SSP - JOURNAL OF CIVIL ENGINEERING

Technical University of KošiceCivil Engineering Faculty

SSP - JO

URNAL OF C

IVIL ENGINEER

ING

Selected Scientific Papers

Vol. 6, Issue 2, 2011ISSN 1336-9024

SSP - JOURNAL OF CIVIL ENGINEERING Selected Scientific Papers

Volume 6, Issue 2, 2011

ISSN 1336-9024

is an international journal presented the latest research results, trends and future directions in the broad field of civil engineering.

FOUNDER AND PUBLISHER Technical Uiversity of Košice Civil Engineering Faculty Vyskoškolská 4 040 22 Košice Slovak Republic www.svf.tuke.sk EDITOR´S OFFICE ADRESSES Technical University of Košice Civil Engineering Faculty Vyskoškolská 4 040 22 Košice Slovak Republic Phone: +421 55 602 4003 Fax: +421 55 623 3219 e-mail: [email protected] EDITOR-IN-CHIEF

Katunský Dušan, Slovakia SCIENTIFIC EDITORIAL BOARD Kmeť Stanislav, Slovakia Kozlovská Mária, Slovakia Kvočák Vincent, Slovakia Števulová Nadežda, Slovakia Vranayová Zuzana, Slovakia ASSOCIATE EDITORS Bednar Thomas, Austria Keppl Julián, Slovakia Kisilewicz Tomasz, Poland Kolbitsch Andreas, Austria

Korjenic Azra, Austria Kozłovsky Alexander, Poland Lazič Ladislav, Hrvatska Motyčka Vít, Czech Republic Niemiec Witold, Poland Portela Maria Manuela, Portugal Radujkovic Mladen, Croatia Rak Janusz, Poland Singh Amarjit, USA Száva Ioan, Romania Šenitková Ingrid, Slovakia Šiaučiunas Raimunds, Lithuana Tesár Alexander, Slovakia TECHNICAL EDITORS Olejníková Tatiana, Slovakia Stanová Eva, Slovakia e-mail: [email protected]

REVIEWERS Pačaiová Hana, Slovakia Draxler Erich, Germany Bielek Milan, Slovakia Jelínek Vladimír, Czech Republic Dimer Vojtecg, Czech Republic Fazekašová danica, Slovakia Vajsáblová Margita, Slovakia Přívratská Jana, Czech Republic Sičáková Alena, Slovakia Kmeť Stanislav, Slovakia Kvočák Vincent, Slovakia Kormaníková Eva, Slovakia Böszörményi Ladislav, Slovakia Očipová Daniela, Slovakia

© Technical University of Košice, Civil Engineering Faculty, Slovak Republic

EDITORIAL The Journal of Civil Engineering, SSP (Selected Scientific Papers) was established in 2006. This effort, led by FCE TUKE creates opportunities for staff and postgraduate students at FCE TUKE to publish the results of their research activities in English for the general scientific and professional community.

This journal and its editorial board have taken their commitment very seriously; to publish only original research results of operations, as evidenced by the fact that from the very beginning, the issue regarding originality, and scientific contribution may be reviewed by two opponents (one from Slovakia and the other from abroad). Several journals were issued as a result of scientific publications and scientific contributions which were hosted at professional events - Scientific conferences and seminars.

The journal is intended to publish the contributions in the fields of: civil engineering (structural engineering), problems concerning the architectural design of buildings, building construction, civil engineering and road construction technology which includes construction management. The journal is published bi-annually and is available online at the FCE TUKE website.

After more than six years of operation in SSP - Journal of Civil Engineering, we aim to create the option to publish the results of research activities externally. We would also like to address our scientific colleagues from abroad to participate on the editorial board of the journal SSP - Journal of Civil Engineering to expand the scope of the journal with the assistance of our partners from abroad, especially those with which FCE TUKE has conducted long-term research and maintains working contacts.

Our goal is to improve and expand publication manifestations so that contributors with a serious interest may be included in the journal’s databases, thereby enhancing its status and recognition from the scientific community.

The newly revamped journal hopes to compete for the favour of readers not only at FCE TUKE, but all whom we maintain long-term good business contacts with. I trust you find the way to those who regard the development of scientific disciplines of Civil Engineering with the same enthusiasm as I do.

Dušan Katunský editor in chief


Volume 6, Issue 2, 2011

ISSN 1336-9024

Contents

Air-handing systems and their evaluation in term of microbial pollution of treated air.........................................................................................................................................Knížová Katarína, Vranayová Zuzana

.......5

Solar chimney.....................................................................................................................Kováč Martin, Vranayová Zuzana, Košičanová Danica

.....17

Applicability verification of in situ solidification/stabilization technology in terms of environmental burdens clean up – pilot testing on the sites in the Czech Repub-lic and Albania…………………...……………………………………………………....Copan Jozef, Bálintová Magdaléna, Urban Ondrej

.....29

Prismatic tensegrity systems.............................................................................................Olejníková Tatiana

.....39

The influence of chemical admixtures on wather resistance of gypsum materials......Ahmad Mohamed

.....47

The load-carrying capacity of the eccentrically-compressed reinforced-concrete columns strengthened with loading……………………………………..........................Blikharskyy Zinoviy, Tsariov Evgen, Khmil Roman

.....57

Experimental tests of steel column to concrete wall connection……………………....Janas Lucjan, Kozłowski Aleksander, Klich Rafał

.....63

Nondestructive tests of laboratory models based on elastic waves measurements and artificial neural networks……………......................................................……….....Nazarko Piotr, Jurek Michał, Ziemiański Leonard

.....75

Technological progress in production, logging and processing of the biomass............Niemiec Witold, Stachowicz Feliks, Szewczyk Mariusz, Trzepieciński Tomasz

.....85

Analysis of failures of the Krosno water network...........................................................Pietrucha Katarzyna, Studziński Andrzej

.....93

Authors´ Guidelines ............................................................................................................ ...101

3

Selected Scientific Papers Vol. 6, Issue 2, 2011

Air-handling systems and their evaluation in term of microbial pollution of treated air

Katarína Knížová, Zuzana Vranayová

Technical University of Košice Civil Engineering Faculty, Institute of Building and Environmental Engineering

e-mail: [email protected], [email protected]

Abstract

The subject of this article is the evaluation of air-handling systems in term of microbiological contamination of treated air. It was designed the methodology of microbiological survey for the purpose of research, in which was evaluated existed air-handling systems in Košice. The aim of this survey was to show the air-handling units and air conducts as potential sources of microbiological pollution in the internal environment of buildings. It is needed to follow hygienic requirements for elimination of microbiological contamination in the design phase, installation phase and during their operation. For this purpose, the controls activities were defined for individual equipments of air-handling systems and designed the methodology of risk analysis. This analysis is tool for identification of possible undesired conditions, definition of their failures, consequences. This is the background for improvement of system design and operation from hygienic aspect.

Key words: air-handling system, microbiological survey, risk analysis, hygienic aspect

1 Introduction

The role of ventilation and air conditioning systems is to provide a hygienically superior conditioning and distribution of air in the internal environment of buildings. In the case of neglected operation and insufficient maintenance, the device itself becomes a source of pollution. The specific type is microbiological contamination, such as bacteria, fungi, viruses. Germs are gated in the indoor air in form of an aerosol, in the device they can cumulate and reproduce by the desirable conditions. This option is regarded very rare by design and operation of ventilation systems in Slovakia nowadays. It confirms the fact that there isn’t sufficient framework for properly design and operation of these systems in terms of hygiene. The presence of microbes in air can cause some allergies and infections as well as different diseases (Legionary illness, Pontiac fever, fever from humidifier, etc.). The microbiological survey of existing ventilation systems in selected buildings in Kosice has shown the large contamination of inner surfaces of the individual components. The lack of control and

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treatment caused the contamination of air passing ventilation system; even through the quality of internal environment was satisfactory. It is important, to pay attention to hygienic control of ventilation systems and to incorporate the schedule of checks into the operation.

2 Microbiological survey of existing air-handling systems and indoor environment

The microbiological survey of air-handling units and indoor environment is aimed to determine of a contamination of individual equipment components and an efficiency of systems in term of microbiological quality of supply air.

2.1 The methodology of microbiological survey

The 4 steps were suggested within the frame of survey, that allow to know the under consideration system and to evaluate the quality of its activity in compliance with the legislation and standard terms of Slovak as of the European Union. The series of basic steps:

1) finding the fact about equipment (type of unit, operation and maintenance), 2) risk assessment of microbiological contamination and determination of the sampling

points, 3) sampling of air samples, samples from the surfaces of equipment and water samples

for the humidification and cooling, 4) evaluation of the measurements, determination of pollution and measures design.

Taking of samples was carried out according standard operating procedures for investigation of microbial contamination in the building internal environment [1]. Samples are evaluated in the laboratory in terms of two biological indicators, and that are the presence of the bacteria Legionella pneumophila and the total number of cultivable bacteria at 36°C. The impact method [2] is used for bioaerosol sampling from the air, on which principle the standard aeroskop works. The nature of aeroskop is the air suction through a perforated plate, which is directed over the area with the culture media (Petri dish or so. Agar strips) and exhausted out. Two taking of samples were made for each measuring point, the culture media was chosen according to the specifications of identifiable organisms. One taking of air lasted 4 minutes; therefore air volume was 400 litres at speeds suction 100 litres per minute. The resulting number of colony forming units deducted from the Petri dish was multiplied by a factor for expressing the total number of bacteria in a volume 1 m3 of air drawn by active suction. Microbial contamination of water for cooling or humidifying was determined from samples in volume 1 litre, which were collected in the sterile glass bottles. The water is then filtered in the laboratory and the filter is given to cultivation at the culture medium by species of identified bacteria. The culture medium for bacteria Legionella pneumophila consists of activates carbon, yeast extract and cysteine (BCYE agar). The taking of samples from surfaces of equipment and air conducts was made by the swab method, i.e. sampling by means of the bleeder tampon humidified by the sterile saline. The wiping area is 10 cm2; it is wiped twice in two directions perpendicular to each other.

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2.2 The results of microbiological survey

The operation of 12 ventilation systems in buildings of private and public sector, e.g. office buildings, bank, sport hall etc. was evaluated during the months from April to December 2009. All systems except one were operated intermittently by operation of indoor environment or by user needs. Every system contained supply duct, ventilation unit with air filtration, air heating, air cooling, heat recovery, with air dehumidification in one case, and duct to supply of air to the interior with end elements. One ventilation system contained cooling tower. The samples evaluation was made in accredited laboratory according by standard cultivation methods for detection the total number of bacteria and for detection of Legionella pneumophila. A total, 62 air samples, 78 samples from surfaces and 1 water sample were taken. In the air samples and samples from internal surfaces only the total concentration of bacteria cultivable at 36 °C were identified, bacteria Legionella pneumophila didn’t identify. Either monitored indicators were identified in the sample of cooling water, the total concentration of bacteria in the value 2,4.105 CFU/l and bacteria Legionella pneumophila in the value 640 KTJ/l. Measuring data comply with values according by German guidelines VDI 6022 Hygiene Anforderungen an raumlufttechnische Anlagen – Blatt 1 und 2 (see Table 1).

Table 1: Limit concentration of biological indicators in cooling water [3]

Biological indicator Limit concentration [CFU/ml] The total concentration of bacteria 10 000 Legionella pneumophilla 10

On the internal surfaces of ventilation unit and air ducts was visible the particulate matter pollution, which was reflected in the measured values of bacteria. The ventilation units are operated in the time 2 – 25 years as well as distribution systems, usually without any mechanical cleaning or chemical treatment. Only ventilation units of System 09 and System 10 in office building are regularly cleaned twice a year. Most of systems are used intermittently only by user needs. It is other significant risk factor for clogging of internal surfaces and creating of cultivating medium for microbiological contamination, except age of devices. The high degree of contamination on internal surfaces of evaluated ventilation systems is caused by inadequate operation in terms of hygiene air treatment. The whole distribution system of ventilation units in the first office building should be excluded from operation as well as air diffuser in systems 05 and 08 by according to requirements of German standard DIN 10 113-3 [4]. These components represent a high hygienic risk in treatment of supply air (see Fig. 1). The concentration of bacteria in indoor air measured near the air diffusers are below the limit of category “very low” indoor air pollution according by legislation of European Union, despite the finding high surface contamination. In two cases was concentration in supply air into internal environment higher than limit value 500 CFU/m3 that is determined in Order No. 259/2008 Ministry of Health of the Slovak Republic for residential area. The concentration of bacteria in supply air after passing through ventilation system was increased in eight systems (it is 66,6 % from total number) in compare with the concentration of bacteria in the intake

7


air. This fact shows negative impact of air ducts and ventilation unit on microbiological contamination of supply air (see Fig. 2).

Figure 1: The concentration of bacteria in samples from surfaces and comparison with requirement of standard DIN 10 113-3

Figure 2: The concentration of bacteria in air samples and comparison with requirement of Order No. 259/2008 Ministry of Health of the Slovak Republic

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2.3 The evaluation of systems operation

The operation quality of these systems was evaluated by comparison of praxis with requirements that are based on standard STN EN 13 779 [5], German guideline VDI 6022 [6] and publications of American society NADCA [7]. It was defined 5 significant requirements for hygienic operation of ventilation systems. They are:

1) relative position of intake and exhaust openings and control of pollution of intake openings,

2) the class of the filtration – two-stage air filtration with recommended class F7 (minimum F5) for predfilter and class F9 (minimum F7) for end filter, one-stage air filtration with minimum class F7,

3) interval of filter exchange – on the basis of allowed pressure loss respectively filters of the first stage once a year, filters of the second stage once two years,

4) control and cleaning of internal surfaces of ventilation unit, 5) availability (inspection chamber) and cleaning of internal surfaces of air ducts during

operating time.

Table 2: Meeting the requirements for the operation of ventilation systems

The requirement is met YES – PARTLY – NOW Air filtration Ventilation

system Position of

intake/exhaust openings Filter class Exchange

interval

Cleaning of unit internal

surfaces

Availability and cleaning of air ducts

System 01 a 02 YES NOW YES NOW PARTLY System 03 YES NOW YES NOW NOW System 04 YES NOW YES NOW NOW System 05 PARTLY NOW YES NOW NOW System 06 YES PARTLY YES PARTLY NOW System 07 NOW PARTLY YES PARTLY NOW System 08 PARTLY NOW YES PARTLY NOW System 09 YES NOW YES YES NOW System 10 YES NOW YES YES NOW System 11 YES NOW YES NOW NOW System 12 YES NOW NOW NOW NOW

3 Possibilities of prevention and elimination of microbiological contamination in air-handling systems

There are several options for removal of microbiological contamination, in existing systems. The aim is to minimize the impact on human health – the user of internal space, which is supplied by the system. We can divide the pollution of air-handling systems by individual components into:

1) the pollution of internal surfaces in air-handling units and air conducts, 2) the contamination of water for humidifying or water for cooling, 3) the pollution in the supply air.

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3.1 Methods for removing of microbiological contamination from internal surfaces of air conducts and air-handling units

Cleaning of internal surfaces of air conducts and surfaces of individual components has three basic reasons:

1) distorted the function of system, 2) threat of fire protection, 3) health risk from the release of established pollutants [8].

Cleaning of internal surfaces in order to maintain hygienic treatment of supply air is the latest reason within the era of air-conditioning systems, because established dirt and dust on internal surfaces of components and ducts may provide ground for microbial growth by the presence water and moisture. The first step is to remove the solid impurities by mechanical cleaning, either with the air stream or by cleaning brush. The effect of mechanical cleaning may increase an additional chemical treatment of cleaned internal surfaces. Disinfectants in the form of solution or foam have an antibacterial effect and reduce the risk of re-growth of bacteria colonies in treated areas.

3.2 Methods for elimination of microbiological contamination of water in air-handling system

Water humidifiers, evaporative condenser and open cooling towers for heat dissipation from the cooling water present risk of humid environment that provides suitable conditions for growth and reproduction of microorganisms. The efficiency of some methods for disinfection of water for air humidifying or cooling water is influenced by the corrosion of materials, production of scale and deposits on internal surfaces, which provide fertile ground for the microbial activity [9]. Oxidizing or non-oxidizing biocides are used for control of microbial activity in water. Halogens on the base of chlorine or bromine are used most frequently from oxidizing biocides. The main disadvantages of dosage oxidizing biocides are the increased effect on corrosion of materials in the system and the dependence of disinfection on the pH of water. We can eliminate these disadvantages with the application of water disinfection by chlorine dioxide, which has high efficiency even at low doses. Disinfection by non-oxidizing biocides is the second possibility. It is more stable and longer-term operating. The physical methods for disinfection of water systems are disinfection with ozone and UV radiation. The main disadvantage of these methods is weak effect on biofilm degradation, what causes repeated microbiological contamination in the short term. This water disinfection doesn’t decrease the water quality; don’t influence chemical composition and pH of water.

3.3 Methods for elimination of microbiological pollution in supply air

The removal of pollutants and microorganisms in the supply air can be achieved by applying the following methods:

1) air filtration, 2) air disinfection by UV radiation.

Air filtration is effective at removing of particles and demands on minimal filtration classes according to the required quality of supply air are part of the standards. The fundamental demand in terms of hygiene is the application of two-stage filtration. Disinfection system of

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air and internal surfaces by ultraviolet lamps (UVGI system) [10,11] can be applied to the recirculation air, directly in ventilation chamber, to the supply air and also for control of microbial growth on internal surfaces of the individual components. This method allows directly deactivation and destruction of biological pollution or undesirable gaseous components in the air. We recommend that this method is always used in parallel with air filtration, not to replace that mechanism.

4 Activities for safety of hygienic air treatment in air-handling systems

It’s important to think over hygienic aspects of the work of ventilation systems in their design, construction and in actual operation. There are introduced base conditions on air-handling systems and activities in this part, which have to be provided in this three phases in order to observe microbiological quality of supply air into internal environment.

4.1 The design phase of air-handling systems

In the design phase, it’s important to apply so approach that assumes a minimum of pollution sources and maximum availability of equipment for cleaning and disinfection. The bases for such design are valid standards and guidelines of Slovakia, as well as the European Union. When we go out from these rules and from survey results of air-handling systems, we have to put the accent on the following facts by their design: location intake of fresh outside air away from sources of pollution with air suction velocity

< 3m/s [12], the short air conduct between air-intake and air-handling units, available for cleaning, accountable filter choice on the basis of required internal air quality, according to purpose

of internal spacing and to assumed quality of outside air in given location, by [5], two-stage filtration with observance of minimal requirements of standard STN EN 13779

and guideline VDI 6022, by [3,5], maximum humidity around filter material < 80 %, measuring the pressure in the filter chamber, to prevent air flow out of filter material, protection of heat exchanger for heat recovery on the side of exhaust air, to ensure the

greater pressure on the side of supply air as on the side of exhaust air, condensation bath with a functional drainage of condensate in the condenser chamber, to prioritize steam humidification or humidification with fresh water, not circulation water,

to ensure the technical possibility of disposal and drying of humidification chamber in the case of decommissioning,

drops eliminator and functional drainage of condensate after air cooler and air humidifier, suitable material and finish treatment of air-handling units and air conducts in order to

minimize accumulation of dirt on their surface (the relationship of surface roughness and air velocity),

isolating of equipment and air distribution systems in areas of possible occurrence of condensation on the internal surfaces (no insulation on the internal surface),

access to all internal parts of air-handling units, by [5], inspection openings on the air conduct system, by [13].

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For effective maintenance of these facilities, it is important at this stage to ensure the technical availability of each component in air-handling units and air conduct for mechanical cleaning, for application of physical or chemical disinfection of air, water and internal surfaces in systems.

4.2 The phase of construction and activation of air-handling systems

Located components of ventilation systems on the site can be polluted by solid dirt, foliage and biological materials. These components should be inspected before installation in to systems in terms of pollution or damages. A found pollution and structural deficiencies must be removed or damaged parts must be replaced with new ones. It is needed to control following activities and equipments of air-handling systems: drain of condensation water in chambers of humidifier and air cooler, air tightness of whole system, undesirable by-pass of air in filter chamber, availability to system components and to inspection chamber, functional of equipment for chemical or physical disinfection of air and water for air

humidifying or air cooling, max allowed humidity in filter chamber.

4.3 The operation phase of air-handling systems

The present practise in Slovakia within operation of air-conditioning systems is especially aimed at function of all equipments. This is mainly reason for periodic services controls of air-handling units. Ones of the results from realised survey is the frequency of this control, which are realised once or twice a year like spring and autumn service in time when the character of equipment operation is changed (heating/cooling period). It’s needed to incorporate the control in terms of hygienic operation of system in the control schedule. This may be made by extension of existing control schedule or by increase the frequency of controls. The total hygienic control of full air-conditioning system must be realized once a year for a unit with humidifying, for a unit without humidifying is interval or control 2 years. Every control of equipments should bring the answers on concrete questions for individual components of whole system (see Table 3). Table 3: Example of questions for hygienic control of air-handling systems, working by [14]

Equipment Control questions Outdoor air intake Where is located?

Is entry of fresh air limited by dirt, unwanted objects? Are there any sources of pollution near (parking, extracted road...)? Is open for exhaust air located at a distance min. 2 m? Is the occurrence of standing water, biological waste (bird droppings) in the vicinity? Are there a cooling tower? At what distance?

Air cooler Is it available for cleaning? Is its surface clean? Are there any problems with water condensation?

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Air filter The type of filter? Does go the whole volume of air through the filter material? Is pressure drop of filter gone over? Are there visible pollution or sensible odour?

Condensation chamber

Is it available for control and cleaning? Is clean, without sediments and visible deposits? Are there water condensation, sensible odour or water leak? Is drain clean and functional?

Water humidifying (Air washer)

Are all the jets functional? Is collection bath clean, no overflow; is drainage from the bath through and functional? Is applied water disinfection functional (e.g. adding biocide)?

Supply air ducts Are clean? Are closed without air? Are fire valve opened? Are revision openings closed? Is there line up of flexible ducts? Is flexible duct without damage or crack? Is there by-pass or any problems with air distribution?

Air diffuser Are they clean? Is not air flow limited? Is air supplied in determined volume? Is regulating and control mechanism in operation?

Needed frequency of controls is individual for every system that is specific by its structure and operating mode. These controls should be the part of a maintenance plan, which is based on these recommendations and, of course, reflects the time and economic severity of the necessary controls and measurements. The guidelines VDI 6022 that was noted above contain recommended intervals and activity rate for controls of air-handling units.

Table 4: Selected control activities by VDI 6022 for air-handling systems [15]

Equipment Control activity Measure Interval inspect for contamination and damage replace the filter 3 months check the differential pressure replace the filter 1 month Air filter filter change in 1./2. stage 12/24 months inspect for contamination, damage and corrosion clean and rectify 3 months

check/cleaning the condensate bath clean and rectify 3/6 months Heat exchanger

check the condensate drain rectify 3 months inspect for contamination, damage and corrosion clean and rectify 6 months

cleaning of parts of the fan in contact with air 12 months

inspect the drive renew the belt 12 months Fan

inspect the flexible connection renew the connection 12 months

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5 Application of risk analysis in air-handling systems

Intuitive assessment of potential hazard is in progress unconsciously and unsystematically and is the part of everyday life. Conscious and systematically assessment of potential hazards, which are the parts of different processes, is the subject of risk science. This evaluation of potential hazard is aimed at a specific project, which may be some process, activity or object (process of shopping centre building, production of steel construction, manufacturing plant, etc.). Risk analysis is basic element of risk engineering that is necessary condition for decision about risk, and therefore the basic process in the risk management [16]. Risk engineer tries to find these possible hazards and to estimate a process of events that could occur in individual cases. The application of risk analysis in air-handling systems could be a suitable tool for identification of risk elements, activities and for definition of necessary controls and their frequency for purposes of hygienic systems operation. In this case, the analysis project is activity connected with design, operation and maintenance of air-handling systems in terms of possible microbiological contamination of treated air in the individual components and supplied to the internal environment. On the basis of available information about general methods of risk analysis, there were worked two ideological proposals for risk analysis of air-handling systems in terms possible microbiological contamination of supply air. The first proposal represents so-called single-step analysis by application of method “Universal matrix of risk analysis (UMRA)” in full scale. There will be estimated realisation of possible hazards and their sources. On the basis of that guess, expected unconsidered conditions can be identified and numerical evaluated by importance of their effects. The second proposal is consists of three separate parts, it represents so-called three-step analysis with using of partly general methods of risk analysis. The first step is based on method UMRA but only in reduced form, procedures of method FMEA (Failure Mode and Effect Analysis) will be used for the second and the third step. The result will be a numerical evaluation of undesirable conditions by three parameters with the aim to set final RPN index. By this design of risk analysis method for air-handling systems, it is assumed to use the single-step analysis mainly in design phase of systems and the three-step for risk evaluating in operation phase of existing systems. Both ways can be worked by only one expert (risk analyst) but it is recommended teem-work with min 3 members. Air handling unit is the basis for risk analysis of air-handling systems that can provide for elementary air treatment. There are supply of fresh air, air filtration, air heating or cooling, air humidizing, supply of treated air into the room and exhaust of waste air. The components, which will be provided for these activities, are the segments of project. The microbiological contamination of treated air in unit and transported by distribution system into internal environment is project aspect. As sources of hazard were identified:

dirt on internal surface, contaminated air, contaminated water.

On the basis of present knowledge and results from realised survey, there are defined total 11 undesirable conditions, which resulted from logical equivalency of hazard sources and project segments: intake of polluted outdoor air,

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dirt on surface of intake openings, or intake air conduct, pollution on the surface of filtration material, passing of contaminated air through filtration material, dirt on surface of air heater or air cooler, occurrence of contaminated water in chamber of air heater or cooler or on the surface of

plates, contaminated water in system of air humidifier, passing of contaminated air through equipment for heat recovery, dirt on the surface of fan, polluted internal surfaces of chambers in air-handling unit and of air conducts (or air

diffuser).

Figure 3: Proposal of three-step risk analysis for air-handling systems

6 Conclusion

The results of microbiological survey showed significant contamination of ventilation systems and their impact on the quality of supply air into the indoor environment. The comprehensive approach to hygienic treatment of air in these systems is important through the design phase, construction and operation phase. Regular answering of control questions by lists provides the required efficiency and control of all necessary hygienic activities. The question remains by suitability of proposed risk analysis procedure for air-handling systems, which must be verified by applying on the systems included in microbiological survey.

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Acknowledgements

This article was written as a solution of project “Support Centre excellent integrated research advanced building structures, materials and technologies, the promotion of operational research and development program funded by the European Regional Development fund. ITMS Project code: 26220120018 and of project VEGA 1/0079/10 „Smart administrative buildings and related progressive indoor technologies in combination with low greenhouse gases level renewable energy sources”.

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Solar chimney

Martin Kováč, Zuzana Vranayová, Danica Košičanová


e-mail: [email protected], [email protected], [email protected]

Abstract

The aim of the paper is to illustrate results obtained from the solar chimney geometry analysis influencing mass flow of the air at the first part. The analysis was performed in CFD software Star CCM+. The task was solved as if quasi-time dependant with a volatile sun location in the sky as well as volatile outer temperature. Content of the second article part is devoted to a comparative analysis of both theoretical and experimental results arising from the application of the solar chimney built over the hall of Faculty of Mechanical Engineering, Brno University of Technology (BUT), Czech Republic.

Key words: solar chimney, computational fluid dynamics, passive ventilation

1 Introduction

At first, some brief description of the so-called solar chimney. As a matter of fact it is a vertical shaft (pipe, chimney) with glass wall through which solar beams go through impacting and at the same time warming up the absorber surface. This causes the escalation of absorber´s surface temperature. As a result of temperatures difference between the absorber and ambient air there is a spontaneous heat transfer arising from the absorber´s surface into the air. This effect is can be explained by the Newton cooling law. According to this law the heat transfer into a liquid (the air) evokes an expansion in it resulting in decrease of its mass. The air becomes thus lighter and rises in direction against the gravity.

2 Solar chimney – CFD analysis in Star CCM+

The solar chimney schema is displayed on Figure 1. Its geometry was set up as follows (Table 1). The calculation is based on the sun location change over the course of a day, change of solar radiation intensity and outer temperature change (Table 2). The simulation of the solar chimney in Star CCM+ includes only the windlessness conditions without the dynamic wind

17

Martin Kováč, Zuzana Vranayová and Danica Košičanová

impact. The geometric model was created in Star CD software from which it was afterwards exported in file format of Parasolid to simulation CFD tool of Star CCM+.

Figure 1: Solar chimney model with light absorber on its rear side

Table 1: Parameters of solar chimney´s geometry

B [m] 0,35 0,45 0,65 0,95 L [m] 1,0 2,0 3,0 4,0 H [m] 3,0 4,0 5,0 6,0 Ainlet from Aoutlet [%] 25 50 75 100

Table 2: Climatic conditions for simulation day – as of July 21

Time 08:00 09:00 10:00 11:00 12:00

0SA [°] 100 114 131 152 180

h [°] 34 44 52 58 60 IP [W/m2] 128 230 335 409 435 Θe [°C] 21,2 23,0 24,8 26,5 30,0

18


There was used the FVM method (Finite Volume Method) on which base was created a structural calculation grid (Fig. 2). In general the number of calculation cells ranged from 50 000 to 350 000 cells according to a size of the geometric model. For the calculation convergence and more accurate results of observed parameters to be achieved, the basic calculation grid was compressed in the spots of big gradients. Marginal conditions of the calculation model are stated in the following table (Table 3).

Figure 2: Calculation grid with local compression

Table 3: Solar chimney´s features

Surface Parameters Glass Sidewall Absorber

area Bottom surface

Upper surface

Heat transfer coefficient [W/(m2.K)] 5,5 0,297 0,289 - -

Material surface Glass Metal plate

Metal plate

Metal plate

Metal plate

Surface finish - Black paint

Black paint

Black paint

Black paint

Surface emissivity [-] 0,15 0,92 0,92 0,92 0,92 Surface transmissivity [-] 0,75 0 0 0 0 Roughness height [mm] 0,0015 0,15 0,15 0,15 0,15

Physics model:

three dimensional, steady, turbulent flow – RANS, turbulence model – Realizable k – ε

Two Layer

boundary layer: Two-Layer All y+ Wall Treatment, Two-Layer Type – Buoyance Driven (Xu),

radiation – Thermal Radiation, S2S, solar Loads, solver – Segregated Flow

OUTLET

INLET

19


2.1 Results

Fig. 3 depicts the influence of the “B” ventilation shaft´s depth on air flow happening at solar chimney´s constant width “L = 1,0 m” and height “H = 3,0 m”. Theoretic assumption was based on that the highest values would be reached for an option with “B = 0,95 m”. This presumption was correct as per the results of simulation. The graph on the right of Fig. 3 illustrates that the air flow is not directly proportional to the rising depth of solar chimney “B”.

0

0,01

0,02

0,03

0,04

0,05

0,06

0,07

0,08

0,09

0,1

8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00

Mas

s airf

low

[kg/

s]

Time

Depth of ventilation shaft B = 0,35 mDepth of ventilation shaft B = 0,45 mDepth of ventilation shaft B = 0,65 mDepth of ventilation shaft B = 0,95 m

00,10,20,30,40,50,60,70,80,9

11,11,21,3

1,3 1,9 2,7

Gra

dien

t flo

w[-

]

Depth of ventilation shaft [-]

Mass airflow

B = 0,65 m

Reference model Bref = 0,35 m

B = 0,45 m B = 0,95 m

Figure 3: Influence of solar chimney´s depth B on air flow

Fig. 4 shows the influence of parameters “B” and “L” on air flow through the solar chimney. A linear dependence of air flow´s changes at different values of “L” and constant depth “B” can be contemplated on the left chart. The graph on the right side displays a well-visible tendency of air flow at constant width “L” and volatile depth “B”. It is clear from the results that the increase of the ventilation shaft´s depth does not cause a dramatic raise of air flow.

00,030,060,090,120,150,180,210,240,27

0,30,330,360,39

1,0 2,0 3,0 4,0

Mas

s airf

low

[kg/

s]

Width L [m]Depth of ventilation shaft B = 0,35 mDepth of ventilation shaft B = 0,45 mDepth of ventilation shaft B = 0,65 mDepth of ventilation shaft B= 0,95 m

00,030,060,090,120,150,180,210,240,27

0,30,330,360,39

0,35 0,45 0,65 0,95

Mas

s airf

low

[kg/

s]

Depth B [m]

Width of ventilation shaft L = 1,0 mWidth of ventilation shaft L = 2,0 mWidth of ventilation shaft L = 3,0 mWidth of ventilation shaft L= 4,0 m

Figure 4: Influence of solar chimney´s depth “B” and width “L” on air flow

20


The analysis of the solar chimney´s geometry was considering the change of area for air inlet and outlet as well. Compared were also results of solar chimney with different height “H”. The results of air flow influenced by the given parameters are shown on Figure 5.

0

0,01

0,02

0,03

0,04

0,05

0,06

0,07

0,08

0,09

0,1

25 50 75 100

Mas

s airf

low

[kg/

s]

A inlet / A outlet [%]

Mass airflow

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

1,3 1,7 2,0G

radi

ent f

low

[-]

Heigth of ventilation shaft [-]

Mass airflow

Reference modelHref = 3,0 m

H = 4,0 m H = 5,0 m H = 6,0 m

Figure 5: Influence of area of air inlet and outlet and influence of solar chimney´s height on air flow

The aim of simulation was to point out the rate of impact of solar chimney geometry on air flow. We can see from results of numerically simulation, how individual parameters (width “L”, depth “B”, height “H”, dimension of openings area for inlet and outlet) influence on the total air flow. Which parameters have a major impact, and which of them are reflected in the very low rate. The results are applied in real life but we have to remember that the windlessness conditions can last only 20 % of time in the year. It´s clear in this example that we must include the dynamic impact of the wind in the 80 % of time in the year and so count with the temperature difference between the indoor air and outdoor air and the dynamic wind impact. The modeling of the wind impact is very difficult and we need to know the final shape of the building and solar chimneys in order to define the values of the final pressure coefficients and their impact on the both solar chimney treatment and natural ventilation of the building.

3 Practical experiences from the application of a solar chimney

The analysis was performed on a solar chimney installed on the roof of the hall premises (Figure 6) being used as a research lab of the Energy Institute. At disposal was data from experimental measurements in .xls file format (source: Ing. Pavel Charvát, PhD,, Senior lecturer, Dept. Of Thermodynamics and Environmental Engineering). Figure 7 schematically depicts installed sensors – direction and speed of wind stream, speed of air flow in solar chimney, intensity of solar radiation on horizontal and skew surface, air temperature in the hall premises, air temperature underneath the hall´s roof, air temperature at the entrance of solar chimney, air temperature at solar chimney´s outlet, ambient air temperature and finally surface temperature of glass panel and absorbent surface of solar chimney.

21


Figure 6: Solar chimney on hall´s roof - lab of FME BUT (photo – source: Ing. Pavel Charvát, PhD.)

Figure 7: Layout of installed measuring sensors – solar chimney over the hall of FME BUT

3.1 Construction solutions of solar chimney

Transparent part of the solar chimney is made up of 2-layer glass with the slope of 60° from the horizontal surface and southern orientation. The air channel´s inlet is created of PVC pipe

22


with diameter of 380 mm and length of 5 m, the upper part is created of 4-edge area of 200 x 700 mm. External part is made up of galvanized sheet with heat isolation (polystyrene) of thickness of 100 mm. The absorbent area of solar chimney is equipped with black greasy paint. A couple of information with regards to the hall premises. It is a standard hall structure with saw-like roof, having basement, original however insufficient filling constructions (steel windows and entrance gates), suffering from significant heat flow into exterior (heat loss) as well as significant leakage causing the creation of pressure ratio in the building itself.

3.2 Results comparison – as of August 1, 2008

The results from theoretical model of solar chimney (processed by graduant) were within the analyzed day compared to observed data. That day was a sunny day with local occurrence of small cloudiness resulting in local decrease of intensity of solar radiation that can be shown on Firgure 8 (Graph 1 – course of solar radiation intensity). In terms of wind velocity it is possible to see on Figure 8 (Graph 4) a small movement, by 1,0 [m/s] within the time span of 00:00 until 08:00, however the air motion is substantial ranging from 1,0 – 6,0 [m/s] in time window between 08:00 till 23.00. (Graph 2) represents air temperature in the hall (Ti), in exterior (Te) and at the solar chimney´s outlet (Tk). For better visual demonstration purposes temperature differences are displayed on Fig. 8 (Graph 6) as a difference between air temperature at the solar chimney´s outlet and ambient air temperature in the span of 3 – 7 °C or as a difference between air temperature at the solar chimney´s outlet and its inlet ranging from 0 – 14 °C. However the values of measured air flow through the solar chimney shown on Figure 8 (Graph 3) differ from the values set by the theoretical model. The question is what could have caused such a substantial difference in values. From one perspective this can be treated as an error of the theoretical model, on the other hand this can be the result of other reasons such as weather conditions, particularly wind strength and direction. Wind forms pressure ratios in the building´s surroundings as well as in the building itself. Values of air mass flow in the solar chimney between 00:00 and 08:00 are almost the same. Theoretical model computes air flow from the upward pressure arisen from the temperature difference between interior and exterior along with the dynamical effect of wind. It can be seen the wind speed in this time window is low (by 1,0 m/s) following that air flow is primarly determined by the temperature difference in the hall and exterior and the wind impact is minimal. On the contrary, air speed in time between 08:00 and 23:00 is characterized with significant fluctuation following that in this case the wind dynamical impact substantially effects forming the pressure ratios in the hall and its environment. But why in this case did not the wind positively influence the air mass flow in solar chimney? What caused such a substantial decline of air flow in this time span? The distribution of pressure ratios in the building itself is thus essentially influenced not only by the air speed, but also by the direction of air stream. On the Fig. 8 (Graph 5) it can be seen a minimal fluctuation of direction of wind flow which is relatively stable and oscillates around 150° till 200° - southern to southeastern wind. As was already mentioned in the introduction the hall premises suffer from substantially leaking filling constructions through which in consequence of air flow with the direction of 150 - 200° the underpressure can arise in the hall and therefore the air from the hall just because of the leaking constructions is „pulled out“ what in turn can cause this decline of air mass flow in solar chimney. The mentioned leaking filling constructions are located in the norhwestern

23


side of the saw-like roof of the hall. Right in these places there can occur underpressure as a result of such a wind direction.

Legend: Graph 1: [W/m2] – M (solar radiation intensity – measured data) Graph 2: [°C] – Te

[°C] – Ti [°C] – Tk

(temperature in exterior – measured data) (temperature in hall – measured data) (temperature at solar chimney´s outlet – measured data)

Graph 3: [m3/s] – M [m3/s] – T [m3/s] – T,W

(air flow in solar chimney – measured data) (air flow from the temperatures difference – theoretical model) (air flow from the difference of temperatures and wind effect – theoretical model)

Graph 4: W[m/s] – M A[m/s] – M

(wind speed – measured data) (wind speed in solar chimney – measured data)

Graph 5 wind direction [°]

(measured data)

Graph 6: [°C] – Tk,e [°C] – Tk,i

(difference between air temperature at solar chimney´s outlet and ambient temperature – measured data) (air temperature difference between solar chimney´s outlet and inlet – measure data)

3.3 Results comparison – as of August 9, 2008

It was a sunny day again with local occurrence of cloudiness causing decline of solar radiation intensity that can be illustrated on Fig. 9 (Graph1 - course of solar radiation intensity). In terms of wind velocity it is possible to see on Fig. 9 (Graph 4) a small movement, by 1,0 [m/s] within the time windows of 00:00 until 02:45 and 23:00 till 23:59. In time span between 02:45 until 23:00 was happening a gradual rise of wind intensity ranging from 1,0 to 7,0 [m/s]. (Graph 2) represents air temperature in the hall (Ti), in exterior (Te) and at the solar chimney´s outlet (Tk). For better visual demonstration purposes temperature differences are displayed on Fig. 9 (Graph 6) as a difference between air temperature at the solar chimney´s outlet and ambient air temperature in the span of 5 – 11°C or as a difference between air temperature at the solar chimney´s outlet and its inlet ranging from 0 – 7 °C. The values of measured air flow through the solar chimney shown on Fig. 9 (Graph 3) are almost the same as those based on the theoretical model.

Why in this case contrary to the previous instance do the measured results overlap those of theoretical model? Let´s start analysing the data in sequence. The values of air mass flow in solar chimney vary just slightly in time periods from 00:00 to 02:45 and from 23:00 to 23:59. Theoretical model computes air flow from the upward pressure arisen from the temperature difference between interior and exterior along with the dynamical effect of wind. It can be seen the wind speed in this time window is low (by 1,0 m/s) following that air flow is primarly determined by the temperature difference in the hall and exterior and the wind impact is minimal.

24


Figure 8: Analysis as of 01.08.2008

25


Figure 9: Analysis as of 09.08.2008

26


On the contrary, air speed in period between 02:45 and 23:00 achieves significant fluctuation following that the wind dynamical effect considerablyforms pressure ratios in the hall and its surroundings. The question remains why in this case did not happen decline of air mass flow in solar chimney? Why in this case did not the negative influence of wind impact the gauge of air mass flow in solar chimney as it occured in previous example?

Analogous to the former example we were also searching for the reason in dynamical effect of wind, especially in direction of its stream. On Fig. 9 (Graph 5) can be seen a stronger fluctuation of wind stream tendency ranging from 250 – 350° (norhern to western wind). As there are original untight filling constructions located on the northwesternside of the hall´s saw-like roof we suppose that due to the streaming of north to western wind there is overpressure in the hall premises. Subsequently the air is crowded out because of smaller resistance, particularly by the solar chimney itself in this case.

3.4 Conclusion

The aim of this article part was to highlight the results differences obtained from the theoretical analysis on one side and those gained from experimental measurements, searching for possible reasons influencing negatively the running of such equipment. Theoretical model requires further examining, correction so that it is easier and more accurate to predict the behaviour of such equipment under real conditions. It is important to realize there are many factors entering the process which can be individual but as well as rather adherent and linked to each other.

Acknowledgements

This article was written as a project solution entitled “Support Centre excellent integrated research advanced building structures, materials and technologies, the promotion of operational research and development program funded by the European Regional Development fund. ITMS Project code: 26220120018. and “VEGA 1/0079/10 – Smart administrative buildings and related progressive indoor technologies in combination with low greenhouse gases level renewable energy sources”.

References

[1] CD ADAPCO user guide STAR – CCM+. file:///C:/CD-adapco/STAR-CCM+%204.04.011/doc/online/wwhelp/wwhimpl/js/html/wwhelp.htm?context=webworks&topic=star.coremodule.actions.MacroPlayAction

[2] FORMAN, M. Přednášky k předmětu počítačové modelování. Brno: Vysoké učení technické v Brně, Fakulta strojního inženýrství, 2010.

[3] CIHELKA, J. Solární tepelní technika. Praha: T. Malina, 1994, ISBN 80-900759-5-9. [4] BIELEK, B., BIELEK, M., PALKO, M. Dvojité transparentné fasády budov, 1. diel.

Bratislava: Coreal, 2002, ISBN 80-968846-0-3.

27


[5] BIELEK, B., BIELEK, M., KUSÝ, M., PAŇÁK, P. Dvojité transparentné fasády budov, 2. diel. Bratislava: Coreal, 2002, ISBN 80-968846-1-1.

[6] JUREČKA, P. Proudění a sdílení tepla, Cvičení do předmětu Sdílení tepla a proudení. Ostrava: VŠB Technická univerzita Ostrava, 2006, ISBN 80-248-1083-2.

[7] HYKŠ, P., HRAŠKA, J. Slnečné žiarenie a budovy. Bratislava: Alfa, 1990, ISBN 80-05-00636-5.

[8] RECKNAGEL, SPRENGER, SCHRAMEK. Taschenbuch für Heizung und Klimatechnik. München: Oldenburg Verlag GmbH, 1995, ISBN 3-486-26213-0.

[9] SZÉKYOVÁ, M., FERSTL, K., NOVÝ, R. Vetranie a klimatizácia. Bratislava: Jaga, 2004, ISBN 80-8076-000-4.

[10] HUMM, O. Nízkoenergetické domy. Praha: GRADA, 1999, ISBN 80-7169-657-9.

[11] HALAHYJA, M., VALÁŠEK, J. Solárna energia a jej využitie. Bratislava: ALFA, 1983, 63-123-83.

[12] Údaje z experimentálnych menraní solárneho komína. Ing. Pavel Charvát, PhD., Brno: FSI VUT.

[13] Fotodokumentácia. Ing. Pavel Charvát, PhD., Brno: FSI VUT.

28


Applicability verification of in situ solidification/stabilization technology in terms of environmental burdens clean up – pilot

testing on the sites in the Czech Republic and Albania

Jozef Copan1, Magdaléna Bálintová2, Ondrej Urban3, 1DEKONTA Slovensko, s.r.o., Slovakia

e-mail: [email protected] 2Technical University of Košice

Civil Engineering Faculty, Institute of Environmental Engineering e-mail: [email protected]

3DEKONTA, a.s., Czech Republic e-mail: [email protected]

Abstract

Locations contaminated as a result of human activity have an adverse impact on the quality of soil and represent a serious hazard to the quality of surface water and consequently on the quality of ground water. The paper deals with a progressive remediation technologies - in situ stabilization and their testing in laboratory and field conditions in localities Zhares, Albania contaminated by organic pollutants and Kank, Czech Republic contaminated by heavy metals. A high-lime stabilization process was proposed for the Zhares location and the process proposed for the Kank location was also based on the application of anhydrous lime.

Key words: In situ stabilization, remediation, heavy metals, organic pollutants

1 Introduction

Stabilization/solidification (S/S) is one of the most effective methods to reduce the mobility of various pollutants in the environment. Cement-based stabilization/solidification (S/S) processes have already proved their worth in the treatment of heavy-metal containing hazardous wastes, organic liquid wastes and low-level radioactive wastes [1-6]. For the immobilization of organic liquid wastes in cement matrices highly effective adsorbent materials are used before the S/S treatment, in order to firmly bind the organics to the cement matrix. If organics were straightforwardly admixed with cement, they would affect the cement hydration kinetics by retarding the reactions via formation of a protective film around the

29

Jozef Copan, Magdaléna Bálintová and Ondrej Urban

cement grain, hindering the formation of calcium hydroxide, and accelerating the reaction via modification of the colloidal C–S–H (C=CaO, S=SiO2, H=H2O) gel precipitated at very early stages around the cement grains [7-10].

For stabilization/solidification of heavy metals various combinations of type I portland cement (OPC), lime, type F fly ash, silica fumes, iron (II) or (III), silicates and blast furnace slag have been used in the treatment of soils contaminated with As [11-12].

Several researchers have shown that As immobilization is mainly controlled by the formation of Ca–As precipitates. Another authors [13-14] demonstrated that the formation of Ca3(AsO4)2 and CaHAsO3 precipitates controls the immobilization of As in contaminated soils, which have been treated with cement, lime and pozzolanic material. At the high pH levels (12–13) induced by lime treatment, where a large fraction of As (III) occurs as HAsO3

2−, the precipitation of CaHAsO3 will take place. Within the same pH range, the formation of Ca3(AsO4)2 occurs in the presence of As(V) ions. These precipitates were found to be responsible for the observed reduction in As leachability. Also, research by [15] has suggested that lime addition reduces As mobility in contaminated slurries due to the formation of low solubility Ca–As precipitates such as Ca4(OH)2(AsO4)2.4H2O and johnbaumite, Ca5(AsO4)3(OH).

Moreover, the reaction of alumino-silicious material, lime and water results in the formation of concrete-like products described as pozzolanic. Dermatas and Meng [16] have demonstrated that in quicklime S/S applications, the formation of pozzolanic reaction products may be associated with heavy metal immobilization by sorption and inclusion in pozzolanic reaction products. Therefore, there seems to be three possible As immobilization mechanisms to be considered. These are Ca–As precipitation, sorption or inclusion in pozzolanic reaction products.

The aim of this work is to reduce the environmental problems at two locations – Zhares in Albania, contaminated by petroleum sludge, and Kank in the Czech Republic, contaminated by heavy metals.

The design of the stabilization/solidification process was based on an individual approach to the selected contaminated materials, taking into consideration the physical and chemical properties of the studied materials, local geological and hydro-geological conditions, availability of stabilization additives, etc.

2 Materials and methods

2.1 Locality and contaminated material

Zhares site is situated 10 km from Fier in Albanie. There are approx. 31,000 m3 of oil sludge and oiled sand stored in oil sludge lagoons. A chemical analysis of tested sample is presented in Table 1. These materials contain relatively high content of asphaltenes (about 20 %).

Kank site represents the premises of abandoned mine in the vicinity of Kutna Hora. The material deposited there is weathered ore, mined 50 years ago. Content of arsenic is around 10,000 mg/kg, zinc around 2,500 mg/kg and lead around 3,000 mg/kg (Table 2)

30


Table 1: Chemical analysis of tested sample from Zhares Contents in dry matter Contens in water leachate

Dry matter TOC NEL DOC PAU Phenols Sample

% g/kg mg/kg mg/l mg/l mg/l Albania 93,4 116 78 250 20,2 0,0053 0,207

Table 2: Chemical analysis of tested samples

Sample

Pollutant Unit Weathered ore material

K1

Weathered ore material

K2

Arsenic-pyrite concentrate

K3 As % 0,95 1,03 1,27 Sb mg/kg 47 39 75 Ni mg/kg 609 34,2 30,5 Tl mg/kg < 5 < 5 < 5 Fe % 9,57 9,4 42,40 Zn % 0,18 0,32 0,08 Cu mg/kg 174 472 0,02 Cd mg/kg 7,9 11,1 19,9 Ag mg/kg 36,6 39,6 111 Cr mg/kg 136 66 17 Ba mg/kg 35,8 62,8 11,4 Pb % 0,33 0,28 0,19 Se mg/kg < 3,5 < 3,5 < 3,5 Mo mg/kg < 2,5 < 2,5 < 2,5 Hg mg/kg 1,34 1,22 1,45

2.2 Laboratory testing

Dekonta a.s., Czech Republic in cooperation with the Research Institute of Inorganic Chemistry in Usti nad Labem carried out the laboratory tests of solidification/stabilization in 2007 and 2008, where approximately 30 stabilization formulas were tested.

Different solidification/stabilization formulas, individually proposed for each contaminated material, were tested in order to determine the most suitable binder mixtures. These formulas were based on mixing with the common additives – cement, lime, gypsum, waste products - fly ash, blast furnace slag, etc.

Solidification/stabilization affects were evaluated on the prepared stabilized specimens after one month curing period. Leaching tests based on EU Directive 1999/31/EC and TCLP (Toxicity Characteristic Leaching Procedure 1311U) methods were performed [17,18].

Based on the initial assessment of the contaminated material from the Zhares location the following S/S formulas were tested (table 3) in laboratory conditions.

31


Table 3: Tested stabilization formulas for sample from Zhares (doses of S/S agents per unit of contaminated material)

S/S additives (kg/kg waste) Identification Quick lime Fly-ash Portland cement Clay Water

ALB-LB2-S1 0,3 0,3 ALB-LB2-S2 0,3 0,3 0,5 ALB-LB2-S3 0,3 0,3 0,4 ALB-LB2-S4 0,3 0,3 0,3 ALB-LB2-S5 0.2 0,1 0,5

Based on the detailed information on contaminated materials from Kank, stabilization formulas were proposed and laboratory assessment of stabilization/solidification was performed.

The formulas were proposed with consideration of the result of the laboratory assessments of S/S of similar material from other locations, whereas it was found that the arsenic and zinc contamination can be successfully stabilized using high quick lime stabilization with resulting low soluble arsenate compounds [19,20,21]. The formulas tested for individual contaminated materials can be seen in table 4. As the samples of the weathered ore material Kank 1 and Kank 2 are almost identical, the Kank 2 sample was tested. Symbols S1, S2 and S3 were used to identify individual formulas used for comparison in the entire test cylinder or crushed sample.

Table 4: Tested stabilization formulas for sample from Kank

Stabilization additives (kg/kg contaminated material) Identification Date

prepared Quick lime - Lhoist

Power plant fly-ash - Poříčí

Slag - Chvaletice

water [ml]

K2-S1 1.7. 0.2 0.2 500 K2-S2 2.7. 0.2 350 K2-S3 2.7. 0.2 0.2 400 K3-S1 1.7. 0.2 0.2 250 K3-S2 2.7. 0.2 300

After 4 weeks of curing, the prepared stabilizates were tested in two alternatives – according to the Ordinance of MŽP ČR 294/2005 Coll. The leach tests were performed on cylinders (uncrushed) with diameters of 4 cm and weights of about 100 g. Field trial testing

Field trial tests were completed in order to confirm that used mixing time and binder quality leads to satisfying stabilization results.

32


Pilot tests at Zhares site were executed in July 2008. Based on the results of the laboratory tests, quick lime admixture was selected as the best stabilization formula. Approx. 4 m3 (which is 4.8 tons) of contaminated oiled sand was mixed with 1.2 tons of lime in situ with a dredger (Fig. 1 and 2).

Pilot tests at Kank site started in October 2008. Quick lime (approx. 900 kg) was mixed with 3 m3 (4.5 tons) of contaminated weathered ore material using ALLU screener crusher (Fig. 3 and 4).

Figure 1 and 2: Pilot test at Zhares site, lime application (left) and material homogenization (right)

-----------------------------------------------------

Figure 3 and 4: Pilot test at Kank site, material homogenization (left) and detail of screen crusher (right)

Solidification/stabilization formulas verified during field trial testing are summarized in table 4. Stabilized materials were left on site in order to be exposed to natural environmental conditions. Subsequent monitoring of stabilized material quality parameters (mainly leaching tests) focused on long terms stability has been carried on both pilot sites.

33


Table 4: Solidification/stabilization formulas verified during field trial tests

Cont. Material Quick lime Water

Site kg kg kg/kg cont.

material kg kg/kg cont. material

Zhares 4800 1200 0.25 1500 0.31 Kank 4500 855 0.19 2100 0.47

3 Results and discussion

The results of leach tests of samples from locality Zhares are presented in Table 2. The tests were performed on the granulate, i.e. sample crushed to less than 4 grain size. The purpose was to determine the worst-case scenario and to achieve the target concentration of the dissolved organic carbon (DOC) in the leachate, in order to select the best stabilization formula for the subsequent semi-field assessment.

Table 2: Results of laboratory test – material from Zhares site

Dry content Content in water leachate Dry content TOC NEL DOC PAHs Phenols Sample

% g/kg mg/kg mg/l mg/l mg/l Water leachate limit –hazardous waste 100

Water leachate limit – non-hazardous waste 80

I. Water leachate limit – inert waste 50 0.1

Drinking water standards 5 0.0001 ALB-LB2-S1 98.8 49.5 32 200 8.4 0.52 0.18 ALB-LB2-S2 97.2 49.9 25 700 6.5 0.96 0.06 ALB-LB2-S3 97.2 43.4 30 690 6.6 0.82 0.08 ALB-LB2-S4 98.6 48.4 28 290 8.8 0.76 0.10 ALB-LB2-S5 92.6 48.4 12 720 15 < 0.04 0.09

The results show that quick lime stabilization is effective and results in major immobilization of organic pollutants. The DOC concentration was below 10 mg/l, except for formula S5 (DOC 15 mg/l), i.e. far below the criteria for class I leachability (50 mg/l). The concentrations of pollutants with adverse effects on human health (poly-aromatic hydrocarbons PAH, phenols) were very low in all cases, at under 1 mg/l.

34


Even formula S1 based on the application of only quick lime results a considerable immobilization of organic pollutants. Formulas S2, S3, S4 demonstrate slightly better results in several parameters (phenols). This can, however, be explained by higher dilution of the original contaminated material.

Based on these results, the S1 formula was proposed for the semi-field testing, i.e. the application of quick lime as part of the Assessment of the effects of the soil environment and ground water on the in situ stabilization process.

Executed laboratory and field trial tests have identified that effective immobilization of organic and inorganic pollutants can be reached by lime stabilization method. Admixtures based on addition of quick lime, alternatively in combination with fly ash or other material with large specific surface lead to very low content of pollutants in water leachate.

Stabilized material from Zhares site is characterized by a high alkalinity and conductivity of its water leachates. Content of DOC is very low, between 10 – 12 mg/l. Content of environmentally and human health hazardous pollutants like polyaromatic hydrocarbons and monohydric phenols is very low (table 5).

Table 5: Results of pilot stabilization test at Zhares site – average values

Content in water leachate DOC PAHs Phenols pH ConductivitySample mg/l mg/l mg/l mS/m

Water leachate limit – non-hazardous waste 80

Water leachate limit – inert waste 50 0.1 Drinking water standards 5 0.0001 Leaching test after 1 month (10.9.2008) 10 0.0059 0.096 12.9 791 Leaching test after 3 months (4.11.2008) 12 0.0066 0.135 12.3 313

Leaching test after 6 months (19.1.2009) 12 0.0183 <0,1 12.2 712

From the laboratory test of stabilization of the contaminated material from Kank resulted in the desired increase of the pH of the leachate and reduction of the concentration of heavy metals and sulphates in water leachates (Table 6). The most important fact is the achievement of zinc reduction by 2 to 3 orders and reduction of arsenic concentration in all leachates by 1 to 2 orders. In the case of cadmium, the concentration was below the level of detection.

Arsenic-pyrite concentrate was best stabilized using the formula based on the addition of quick lime and slag. In the case of testing on the monolithic sample, the concentration of the contaminants in the water leachate was below the level for class II of leachability.

Samples of stabilized weathered ore material from Kank site are characterized by a very low content of heavy metals – arsenic, zinc and cadmium in water leachate. Results performed one month after stabilization test completion have shown that contents of all heavy metals are below threshold values for inert waste. Main mechanism of arsenic and zinc immobilization is

35


formation of non-soluble calcium salts - CaHAsO3 and Ca3(AsO4)2. Other heavy metals are stabilized mainly due to increased pH values between 10-12 which intensify solubility of silicon dioxide and oxide of aluminum and subsequently lead to increased availability for the lime reactions (table 7).

Table 6: Results of laboratory test – material from Kank site

Parameter Unit Class II of leachability

Class III of leachability K2-S1 K2-S2 K2-S3 K3-S1 K3-S2

RL mg/l 6000 10000 372 420 380 494 750 pH > 6 11,43 11,01 11,20 11,45 11,74

SO42- mg/l 2000 5000 90,3 184,8 140,6 89,5 112,4

F- mg/l 15 50 0,110 < 0,2 0,116 0,112 0,108 Cl- mg/l 1500 2500 34,49 37,94 37,94 37,94 41,39 As mg/l 0,2 2,5 0,06 0,15 0,06 0,07 0,43 Ba mg/l 10 30 0,044 0,029 0,037 0,038 0,036 Cd mg/l 0,1 0,5 < 0,005 < 0,005 < 0,005 < 0,005 < 0,005

Cr celk. mg/l 1 7 < 0,005 < 0,005 < 0,005 < 0,005 < 0,005Cu mg/l 5 10 < 0,02 0,04 0,03 < 0,02 < 0,02 Ni mg/l 1 4 < 0,01 < 0,01 < 0,01 < 0,01 < 0,01 Pb mg/l 1 5 < 0,05 < 0,05 < 0,05 0,15 0,44 Sb mg/l 0,07 0,5 < 0,07 < 0,07 < 0,07 < 0,07 < 0,07 Se mg/l 0,05 0,7 < 0,07 < 0,07 < 0,07 < 0,07 < 0,07 Zn mg/l 5 20 0,009 0,006 0,033 0,008 0,026 Mo mg/l 1 3 < 0,05 <0,05 < 0,05 < 0,05 < 0,05 Hg mg/l 0,02 0,2 < 0,001 < 0,001 < 0,001 < 0,001 < 0,001

Table 7: Results of pilot stabilization test at Kank site after one month curing period – average values

Parameter Unit WL limit - inert waste

WL limit – non-

hazardous waste

WL limit – hazardous

waste

Leaching test- before

S/S

Leaching test – after

S/S

pH - > 6 2.65 11.9 SO4

2- mg/l 1000 2000 5000 953 259 Cl- mg/l 80 1500 2500 137 13.8 F- mg/l 1 15 50 0.8 0.222 Ba mg/l 2 10 30 < 0.03 0.077 Cd mg/l 0.004 0.1 0.5 0.87 <0.01

Crcelk. mg/l 0.05 1 7 < 0.005 <0.01 Cu mg/l 0.2 5 10 3.1 0.05

36


Hg mg/l 0.001 0.02 0.2 < 0.001 <0.001 Ni mg/l 0.04 1 4 < 0.1 <0.02 Pb mg/l 0.05 1 5 < 0.5 <0.1 Sb mg/l 0.006 0.07 0.5 < 0.7 <10 Se mg/l 0.01 0.05 0.7 < 0.7 <10 Zn mg/l 0.4 5 20 79.4 0.1 Mo mg/l 0.05 1 3 < 0.2 <0.02

Astot. mg/l 0.05 0.2 2.5 1.7 0.05

*) WL – water leachate

4 Conclusions

Laboratory and field trial tests have confirmed that in situ solidification/stabilization is the suitable method for treatment of material contaminated with heavy metals and/or oil hydrocarbons.

Verified quick lime admixtures have shown effective immobilization of the pollutants, have reached EU/Czech water leachate limit values for inert waste and have demonstrated their long term stability. In comparison with other remediation technologies, in situ solidification/stabilization might lead to significant cost optimization.

Acknowledgements

Authors would like to acknowledge the Czech Ministry of Industry and Trade for its financial support (Grant No. FI-IM3/095).

References

[1] OUKI, S.K., HILLS, C.D. Microstructure of Portland cement pastes containing metal nitrate salts. In Waste Manage. vol. 22, 2002, p. 147–151.

[2] HILLS, C.D., SWEENEY R.E.H., BUENFELD, N.R. Microstructural study of carbonated cement-solidified synthetic heavy metal waste. In Waste Manage. vol. 19, 1999, p. 325–331

[3] ANDAC, M., GLASSER, F.P. The effect of test conditions on the leaching of stabilised MSWI-fly ash in Portland cement. In Waste Manage. vol.18, 1998, p. 309–319

[4] DIET, J. N., MOSZKOWICZ, P. SORRENTINO, D. Behaviour of ordinary Portland cement during the stabilization/solidification of synthetic heavy metal sludge: macroscopic and microscopic aspects. In Waste Manage. vol. 18, 1998, p. 17–24.

[5] HAMILTON, W.P. BOWERS, A.R. Determination of acute Hg emissions from solidified/stabilized cement waste forms. In Waste Manage. vol. 17, 1997, p. 25–32

[6] OSMANLIOGLU, A.E. Immobilization of radioactive waste by cementation with purified kaolin clay. In Waste Manage. vol. 22, 2002, p. 481–483.

[7] CHANDRA, S. FLODIN, P. Interactions of polymers and organic admixtures on Portland cement hydration. In Cem. Concr. Res. vol. 17, 1987, p. 875–890.

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[8] POLLARD, S.J.T. MONTGOMERY, D.M. SOLLARS, C.J. PERRY, R. Organic compounds in the cement-based stabilization/solidification of hazardous mixed wastes—mechanistic and process considerations. In J. Hazard. Mater. vol.28, 1991, p. 313–327.

[9] ABD EL WAHED, M.G. Electrical conductivity of Portland cement admixed with some azodyes. In J. Mater. Sci. Lett. vol.10, 1991, p. 1349–1351.

[10] EDMEADES, R.M. HEWLETT, P.C. Cement admixtures. In: P.C. Hewlett, Editor, Lea's Chemistry of Cement and Concrete, fourth ed, Arnold, London, 1998, p. 837–901.

[11] AKHTER H., CARTLEDGE, F.K., ROY, A., TITTLEBAUM, M.E. Solidification/stabilization of arsenic salts: effects of long cure times. In J Hazard Mater vol. 52, 1997, p. 247–264.

[12] LEIST M., CASEY, R.J., CARIDI, D. The management of arsenic waste: problems and prospects. In J Hazard Mater. B76, 2000, p. 125–138.

[13] DUTRÉ V., VANDECASTEELE, C., OPDENAKKER, S. Oxidation of arsenic bearing fly ash as pretreatment before solidification. In J Hazard Mater B68, 1999, p. 205–215.

[14] VANDECASTEELE, C., DUTRÉ, V., GEYSEN, D., WAUTERS, G. Solidification/stabilization of arsenic bearing fly ash from the metallurgical industry. Immobilization mechanism of arsenic. In Waste Manage vol. 22, 2002, p. 143–146.

[15] BOTHE, J.V. AND BROWN, P.W.. Arsenic immobilization by calcium arsenate formation. In Environ Sci Technol vol. 33, 1999. p. 3806–3811.

[16] DERMATAS, D. AND MENG, X., 2003. Utilization of fly ash for stabilization/solidification (S/S) of heavy metal contaminated soils. J Eng Geol 2189, pp. 1–18.

[17] U.S.EPA: International Waste Technologies / Geo-Con In Situ Stabilization/ Solidification Application Analysis Report, 1999,http://www.epa.gov/ORD/SITE/reports/037.htm,

[18] Stabilization/Solidification Processes for Mixed Wastes, U.S.Environmental Protection Agency, 1996, http://www.epa.gov/radiation/docs/mixed-waste/402-r-96-014.pdf.,

[19] URBAN, O., RODOVA, A., COPAN, J. Applicability verification of in situ solidification/stabilization technology in terms of environmental burdens clean up – pilot testing U.S.EPA. In International Waste Technologies / Geo-Con In Situ Stabilization/ Solidification Application Analysis Report, 2009, http://www.epa.gov/ORD/SITE/reports/037.htm

[20] Wimmerová, L., Čopan, J., et al.: The knowledge transfer of in situ remedial techniques – from laboratory to field-scale. In: ConSoil 2010. Salzburg 2010, 95-96

[21] Zídkova, L., Čopan, J.: Remediation technologies in dekonta – verified methods and new approache. In: ConSoil 2010. Salzburg 2010, CD

38


Prismatic Tensegrity systems

Tatiana Olejníková

Technical University of Košice Civil Engineering Faculty, Institute of Construction Technology and Management

e-mail: [email protected]

Abstract

In the paper there is described one class of bi dimensional assemblies of tensegrity systems constituted by prismatic cells with rhombic configuration with triangular bases so-called prismatic tensegrity systems. There are described bi-dimensional assemblies created double grids with three strut cells by a node on cable junction.

Key words: tensegrity system, compression, tension, self-stress, equilibrium, prismatic tensegrity system

1 Introduction

Tensegrity structures are the most recent addition to the array of systems available to the designers. The concept itself is about eighty years old, and it came not from within the construction industry, but from the world of arts. Although its basic building blocks are very simple – a compression element and a tension element – the manner in which they are assembled in a complete, stable system is by no means obvious.

Tensegrity systems are spatial reticulate systems in a state of self-stress. All their elements have a straight middle fibre and are of equivalent size. Tensioned elements have no rigidity in compression and constitute a continuous set. Compressed elements constitute a discontinuous set. Each node receives one and only one compressed element.

There are two kinds of components according to their state of load effect: compression or tension. A second character is included in the concept: compression is inside tension. The compressed entities are islands-they constitute a discontinuous set. Tensioned entities are gathered in a continuous set. (Olejníková, 2010)

A tensegrity system is established when a set of discontinuous compression components interact with a set of continuous tensile components to define a stable volume in space. But it needs to be slightly modified to take into account the following factors:

• Components in compression are included inside the set of components in tension.

39


• Stability of the system is self-equilibrium stability.

Perhaps because of these conceptual difficulties, progress in the realization of tensegrity structures has been rather slow.

2 Geometry of prismatic three-strut cels

For a defined elementaty cell, geometry is characterised by coordinates for the n (n = 3,4,6) nodes of the system. Lenght „s” of struts and „c” of cables can be derived from the coordinates. If topology „struts” and „cables” are defined, then the geometry is qualified by the whole set of coordinates, which is closely related to the self-stress equilibrium.

If topological characteristics mentioned in the definition of tensegrity systems are important, specific attention should also be paid to another characteristic. But it is sufficient to know at this stage that a self-stress state is such that every element is under tension or compression, the whole system being in static equilibrium without any external actions. A node receives three cables and one strut. A necessary condition of equilibrium can be expressed in geometrical terms: the strut has to be inside the solid angle defined by the three cables.

Let us consider a straight prism with a triangular base, its edges are cables. One strut is inserted diagonally to each square face (Fig. 1). A simple way to attain the corresponding tensegrity system will be to operate a relative rotation between the upper triangle and the lower triangle. The generation mode is the basic of the chosen „prismatic system” names simplex, elementary equilibrium. These terms are defined in connection with the relative rotation with angle equal to 30° (Fig. 2, Fig. 3).

Figure 1: Triangular prism Figure 2: Simplex, equilibrium

The simplest idea is to assemble elementary cells so as to constitute a double layer grid, as can be done in a tiling operation. Elementary cells are self-equilibrated and so is their assembly. Several junction can be used: node on node, node on cable, cable on cable. In type 1 (Fig. 5) the junction is operated with a single bracing cable: each of its two ends lies in different horizontal planes, and it is used in a plane configuration leading to a double layer grid (Fig. 4).

40


Figure 3: Twist angle Figure 4: Threecels junction

1 2 3

Figure 5: Three junction models of two cells Planar double layer tensegrity grid is created by using three-struts cells by node on cable solution (Fig. 6). The node coordinates of one cell in the planar grid are in (1) with parameter

10 =k , where “k” is number of node in one cell (Fig. 3)

( ) ( ) ( ) ( ),ksink,kcosk 00 ϕ=ϕ= rkyrkx

( ) ( ) ( ) 1,2,3kfor,0k,3

21-k12

k ==π

+π

−=ϕ z (1)

( ) ( ) ( ) 6,5,4kfor,31,k,3

24-k12

k =+==π

+π

=ϕ rhhz

The node coordinates of all cells in the planar grid, where i,j determine position of cell in the grid, are

( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )kkj,i,,jkkj,i,,jkkj,i, 1y1x1 zzdyydxx =+=+= (2)

)3

(i).cos(j)3

(i).sin(j(j) , )3

(i).sin(j-)3

(i).cos(j(j) yxyyxxπ

+π

=ππ

= vvdvvd (3)

30°

3

1

4

5

6

2x y

0=z

41


( ) ( ) ( ) ( ) ( ) ( ) ,293,

453,2,2,011,

43,

23

2y1x2y1xyx21 vvvvvvvvvvrvrv ======== (4)

( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) 2y1x2y1x2y1x2y1x 87,237,

2116,

496,35,35,24,24 vvvvvvvvvvvvvvvv ========

Figure 6: Planar prismatic tensegrity system By maintaining the principle of elementary self-stressed cells it is posible to modify the equilibrium shape so as to generate double curvature systems, spherical surface with radius R. The elementary cell must be modified by the parameter ko in the equations (1) of the node coordinates of the upper triangles.

The transformation of the node coordinates of the lower layer of planar grid on the sphere with radius R and centre S(0,0,-R) is for 1,2,3k = and parameter 10 =k in equations (1)

( ) ( ) ( )[ ] ( ) ( ) ( )[ ]kj,i,,kj,i,,kj,i,kj,i,,kj,i,,kj,i, 111 zyxzyx ′′′→

( ) ( ) ( )kj,i,coskj,i,coskj,i, vuRx =′ (5)

( ) ( ) ( )kj,i,sinkj,i,coskj,i, vuRy =′

( ) ( ) RuRz −=′ kj,i,sinkj,i,

42


where

( ) ( ) ( ) ( ) ( ) ,kj,i,2

kj,i,,kj,i,kj,i,kj,i, 21

21 R

duyxd −π

=+=

( ) ( ) ( )( )kj,i,

kj,i,arccoskj,i,sgnkj,i, 1

1 dx

yv = (6)

The transformation of the node coordinates of the upper layer of planar grid on the sphere

with radius R+h and centre S(0,0,-R) is for 6,5,4k = and parameter R

hRk +=0 in equations

(1)

( ) ( ) ( )kj,i,coskj,i,cos)(kj,i, vuhRx +=′

( ) ( ) ( )kj,i,sinkj,i,cos)(kj,i, vuhRy +=′ (7)

( ) ( ) RuhRz −+=′ kj,i,sin)(kj,i,

where

( ) ( ) ( ) ( ) ( ) ,kj,i,2

kj,i,,kj,i,kj,i,kj,i, 21

21 hR

duyxd+

−π

=+=

( ) ( ) ( )( )kj,i,

kj,i,arccoskj,i,sgnkj,i, 1

1 dx

yv = (8)

In the Fig. 7 there is displayed the grid composed from three-strut cells transformed on the spherical surface. Fig. 8 is the illustration figure of this transformation, where the point A[x,z,y] is in the tangent plane of the sphere and the point A´[x´,y´,z´] is located on the sphere and it is determined by the parameter d and angles u and v.

Figure 7: Double curvature system Figure 8: Transformation A → A'

z

x

y A

A´

0

v

u

d

z

43


3 Prismatic four-strut cels

In (Olejníková, 2010) there was described the tensegrity system composed of the prismatic four-strut cells. Application of the planar double layer grid is displayed in Fig. 9, spherical grid with one curvatur in Fig. 10 and with double curvature in Fig. 11.

Figure 9: Planar tensegrity system Figure 10: One curvature system

Figure 11: Double curvature tensegrity system

44


4 Prismatic six-strut cels

In this chapter there is displayed planar tensegrity system composed of six-strut cells. Axonometry view and top view of the one cell is in Fig. 12 and Fig. 13, planar grid is in Fig. 14.

Figure 12: Axonometric view of cell Figure 13: Top view of cell

Figure 14: Six-strut cells tensegrity system

45


5 Conclusion

We have tried to give some examples of planar or non planar prismatic tensegrity systems. Some are only geometrical studies without equilibrium considerations. It is not easy to define Tensegrity systems. It could be claimed, that everything in the universe is tensegrity with properties related to the continuum of tensioned components.

Acknowledgements

This work was supported by the VEGA 1/0400/09 „Integrated analysis of intelligent adjustable cable and tensegrity systems“ and by project OPVaV/2008/2.1/01 „Support of centre of integrated research of progressive bilding constructions, materials and technologies“.

References

[1] OLEJNÍKOVÁ T.: Geometry of tensegrity systems. In: Zborník vedeckých prác „Inovatívny prístup k modelovaniu inteligentných konštrukčných prvkov v stavebníctve 2010“.ISBN 978-80-89338-05-4,(2010), s.98-104

[2] MOTRO R.: Tensegrity: Structural Systems for the Future. Kogan PageLimited, 2003. London and Sterling, VA, ISBN 1-903996-37-6, http://www.google.com/books?hl=sk&lr=&id=0n0K6-zOB0sC&oi=fnd&pg=PR7&dq=Tensegrity:+Structural+Systems+for+the+Future&ots=85AsVSIo_l&sig=amBKpKIADyZVPlpc0vVQ03g0OUI#v=onepage&q&f=false

[3] BURKHARDT R.W.: A Practical Guide to Tensegrity. Cambridge, MA 02142-0021, USA, 2008, http://www.angelfire.com/ma4/bob_wb/tenseg.pdf

[4] KMEŤ S.,PLATKO P.,MOJDIS M.: Navrhovanie a analýza tensegrity sústav. In: The international Journal “Transport & Logistics”. ISSN 1451-107X, Č. 18 (2010), s. 42-49

46


The influence of chemical admixtures on water resistance of gypsum materials

Mohamed Ahmad 1

State Higher Vocational School in Krosno Polytechnic Institute, Department of Civil Engineering

e-mail: [email protected]

Abstract

This paper presents the results of the laboratory research concerning the influence of artificial resins on hydrophobic and water resistance features of gypsum materials. The research results prove that inuring gypsum materials in their whole mass is by all means advisable. In this way, it is possible to obtain gypsum materials with good technical parameters making it possible to use them in wider areas in building industry.

Keywords: gypsum material, hydrophobia, water resistance

1 Introduction

Gypsum adhesives are one of the oldest building materials all over the world. Thanks to archaeological research, nowadays we know that gypsum was used in ancient times. Together with the fall of the antique culture, gypsum was forgotten as a binding material. The next traces of using gypsum were found in the epoch of renaissance of sacral objects [3]. In Poland, gypsum was used for finishing works, decorations and as mortar in walls in the 9th century. The beginning of the cement industry resulted in the immediate decrease of interests in gypsum adhesives. After the World War II the lack of building materials caused the increase in the demand for gypsum adhesives in building industry [2,7]. In this period also in Poland the structures producing gypsum were created. Unfortunately, because of the lack of researches and specialist literature concerning gypsum, the technical staff was not numerous and qualified enough and consequently the knowledge and achievements in gypsum industry from the past were forgotten. The Polish gypsum deposits are estimated at 230 million tons and they are one of the richest all over the world. The other important areas of gypsum deposits are among others: the USA, Mexico, France, Chile, Spain [2]. Fast development of the building industry resulted in the need for materials which allow to build quickly, cheaply and well. For certain, gypsum materials with building gypsum as their main component, fulfil

1 PhD. Eng., State Higher Vocational School in Krosno, POLAND

47

Mohamed Ahmad

these requirements. Gypsum stone used in building industry is burnt in the temperature 150-190°C. The product obtained in this way includes among others half-water gypsum, and the rest constituting waterless gypsum – anhydrite and deposit effluents. The product of burning in the ground form is building gypsum. The major advantage supporting using gypsum materials compared to lime or cement in building industry is economy. The advantages of using gypsum materials support the development of gypsum industry in Poland. The most significant advantages of gypsum are: quick bonding and hardening; low volumetric weight; sizeable porosity; frost resistance; white colour and attractive texture. The main disadvantages, on the other hand, are: unfavourable influence of humidity on gypsum materials strength; low malacia factor; quite big gypsum consumption on 1 m3 of the ready product; low adherence to aggregates, in particular to smooth aggregates.

2 Justification for undertaking the research subject

With regard to very favourable advantages, gypsum materials are applicable in wider and wider areas of building industry, however in Poland, compared to other countries, the prevalence of using gypsum in building is still quite low. The major disadvantage of gypsum materials limiting their wider usage in building industry is their susceptibility to water effects. Thus, it is essential to modify some features of gypsum materials such as decreasing their absorbability and increasing their water resistance while at the same time keeping their other advantages unchanged. There have been many researches over increasing water resistance of gypsum materials conducted for a lot of years, however since early eighties the researches have been intensified. The issue of increasing water resistance of gypsum materials is nowadays very significant, topical and up to date [2]. Within the framework of this elaboration in the Department of Building of the State Higher Vocational School in Krosno, the laboratory research was conducted over hydrofobization of gypsum materials. The research was limited to hydrofobization of gypsum materials in the whole mass through introduction of chemical admixtures - synthetic resins to gypsum leavens. Technological operations such as: vibration, compaction, ultrasound etc. were omitted. The attention was mainly focused on the simplicity of the realization technology. Chemical admixtures correcting the gypsum materials features such as decreasing their absorbability or increasing their water resistance were searched for. From the great range of products that are available on the market, several chemical admixtures were chosen and mixed with gypsum leaven. The major criterion of choosing admixtures was their availability, price and lots of other features such as very good adherence, considerable hydrophobicity and their ability to dose them to make-up water or gypsum leaven. The influence of water on gypsum materials is destructive. This feature limits the wider use of gypsum materials in building industry. Gypsum materials in humid state demonstrate the decrease in their strength up to 60-80% and big absorbability reaching 30-50% [1]. The technology of manufacturing gypsum products favours the pore emerging in the structure of those materials. In theory, hemihydrate of calcium sulfate attaches 18,6% of water, however in practice the role of water in gypsum leaven fluctuates between 40-90%. After drying, volumetrically equivalent number of pores come into being [2]. The porosity of gypsum materials particularly influences their strength features, absorbability, capillary absorption of water and a lot of other physical features. The modern technology of building materials should make use of the data concerning the structure of

48


pores in wider scope than it does nowadays. Works of many researchers engaged in the subject and research on gypsum materials are focused on this phenomenon. The researches conducted on increasing hydrophobic features focus mainly on the phenomenon of moistening, absorbability or capillary water absorption.

3 Characteristics of the blank material

The gypsum used in laboratory research was produced by the company “Dolina Nidy” in Gacki (Świętokrzyskie Voivodeship). All researches and markings were based on half-water gypsum (building gypsum). The product from the company mentioned above is an appropriate material for laboratory research for a couple of reasons: high quality of the raw material and production technology (calcination technology) eliminating adhesive effluents during production. For the purpose of assessment of the quality of the building gypsum produced in Poland, a lot of researches were conducted aiming at determining strength homogeneity of this material. The research proved that building gypsum as a basic form of gypsum adhesive available on the market fulfils all the conditions and requirements stated in the norms. The features of control samples are presented in table 1.

Table 1: Features of gypsum control samples

STRENGTH MALACIA FACTOR ABSORBABILITY

Rs Rsm Rz Rzm Nm W/B

MPa Ks Kz %

0,60 11,00 2,86 4,20 1,22 0,26 0,29 34 0,55 12,10 3,39 4,80 1,50 0,28 0,31 31 0,50 13,30 4,41 5,30 1,75 0,30 0,33 27

W/B - Water/Binder; Rs - Strength against squeezing in the dry state; Rsm - Strength against squeezing in the humid state; Rz - Strength against bending in the dry state; Rzm - Strength against bending in the humid state;

Ks - Malacia factor during squeezing; Kz - Malacia factor during bending; Nm - Mass absorbability.

4 Methodology and the research scope

In order to assess the features of gypsum materials correctly, it is essential to establish precise research methodology. Physical and strength features of gypsum materials mainly depend on the way and conditions of the appropriate marking. Consequently, during researches the major attention was focused on the gypsum, distilled water and environment temperature. All measurements were made in the laboratory room protected from draught and sunlight. In accordance with the norm requirements [8,9] the temperature of gypsum, distilled water and the environment during marking was 20±2ºC, and the relative humidity in the laboratory room reaching 65±5%. The purpose of using distilled water in all the researches was to eliminate the influence of chemical elements (admixtures) in tap water on accuracy of the results. These admixtures can aggressively influence the gypsum material. All gypsum materials features were marked on norm trabeculas of dimensions 4x4x16 cm according to the norms [8,9]. The measure of gypsum material strength against water is the value of malacia

49

Mohamed Ahmad

factor expressed by the proportion between samples strength against squeezing (bending) in the water saturated state and strength against squeezing (bending) in the dry state [9]. That is why, while stating the scope of the research, the possibilities of gaining information on the influence of implemented chemical admixtures on waterproof and hydrophobic features of gypsum materials were taken into account. The major technical features of gypsum materials which show the ability and effectiveness of admixtures in strengthening these materials against water are strength against squeezing and bending in the dry state and water saturated state, absorbability and capillary water absorption. All chemical admixtures used in the laboratory research were added/dosed to gypsum leavens in amounts between 0,5-3,5% in relation to gypsum mass.

5 Features of the chemical admixtures used to modify building gypsum

5.1 Silicon resins admixtures

Silicon resins, thanks to their precious features are used in wider and wider areas as specialist materials and auxiliary materials in various economy branches [10]. Some silicon polymers, thanks to their great water resistance features, are used for effective demonstrations of hydrophobic features, so called: “bouncing putty”. Silicon resins including reactive groups are used to modify alkane, epoxy and acrylic lacquers in order to improve their resistance on weather conditions [11]. Silicones are multi-molecular silicon organic built from silicon atoms linked with oxygen atoms and partially linked with carbon atoms. Merging organic and inorganic elements in one silicon polymer molecule results in providing these materials with lots of valuable and usable features. Silicon aids used for hydrophobization of building materials are produced on the basis of methylsilicone resins. They provide the building materials with hydrophobic features while keeping their steam and gas permeability unreduced. They result in the improvement of thermal insulation, they protect from cracking as a result of frost and increase their dirt resistance [10]. Silicon aids, mainly sodium and potassium methylsilicone are used most often for surface protection of building elevations nowadays. Silicone preparations can be used for hydrophobization of building materials both in housing building and industrial building [10]. For the purpose of hydrophobization of building materials, the specific resins are not used but waste products from which sodium or potassium methylsilicone is obtained in the form of water solutions. In order to modify the features of gypsum materials, two silicon admixtures were chosen: Ahydrosil K and Sarsil H-14/R. Ahydrosil K is a silicon resin solution in potassium lye. It is clear and transparent liquid of colour ranging from pale yellow to brown. It is easily diluted with water. Ahydrosil K is used for waterproof impregnation of concrete, bricks, roof tiles, stone and gypsum linings etc. Using Ahydrosil K for hydrophobization of gypsum materials it has to be diluted with water in the ratio ranging from 1:8 to 1:10. Mechanical damage of the elements made in this way does not change their hydrophobic features. Using this method, it is enough to add 15 kg of diluted Ahydrosil K for 1 m3 of mortar. Sarsil H-14/R is a solution of methylsilicone resin in washing benzene. It is used for direct application and it does not require dilution. It is colourless or yellow liquid of low viscosity and the smell of washing benzene.

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5.2 Acrylic resin admixtures

Acrylic resins are derivatives of acrylic acid, more precisely: esters of derivatives of acrylic acid [4]. Materials from these resins has high technical and aesthetic values, however because of its price, products made of this are still treated as luxury products [12,13]. Acrylic resin products appear on the market as solid resins or solutions but among others as dispersions. Elastoplastic copolymers are the main ingredients of mass used to sealing joints in the building industry; variants having > 20% of acrylic acid are dissolved in water. They are also used as capsules with regulated absorbability and water permeability. Acrylic acid is easily dissolved in water. Being kept, it easily undergoes polymerisation forming solid resin. In nickel carbonyls presence, acetylene, carbon monoxide, alcohol react with each other creating acrylic acid ester. For the purpose of laboratory research, the acrylic resin Solakryl SW-100 was chosen. It is a mixture of calcium and sodium acrylic acid salt, containing modifying and netting admixtures. Solakryl SW-100 is a dry product of white colour in the form of dusty powder, designed for reinforcing and sealing grounds, water-resistant impregnation of building materials, combining dusty materials and improving mechanical strength and water-resistance features of cement and gypsum mortars. It is easily dissolved in cold water and water suspensions of mineral substances. Water solutions of Solakryl SW-100 polimerize under the influence of initiators forming cohesive, elastic, insoluble in water gels. Thanks to low viscosity level of the preparation together with dissolved initiators in it, it penetrates through porous materials and polimerizes in the stated time making them insoluble for water. The pace of the preparation combining can be regulated in a wide scope by choosing the appropriate quantities of initiators. Solakryl SW-100 in the quantity of several % - to the cement or gypsum, after a couple of days makes the received moulders durable against squeezing exceeding 35 MPa. Products containing Solakryl SW-100 receive high level of water and salt water solution resistance.

6 The influence of chemical admixtures on water resistance of gypsum materials

6.1 The influence of silicon resin admixtures on water resistance of gypsum materials

The results of the research concerning the influence of silicon resin admixtures on water resistance of gypsum materials are presented in table 2 and graphically depicted in charts - pictures 1 and 2. Silicon resin admixtures accelerate combining of gypsum mass what results in the need to introduce inhibitors simultaneously. As a result of my own research, it can be stated that the best inhibitor for combining is citric acid or potassium citrate. Both inhibitors bring about good results and do not influence negatively gypsum materials strength features. On the basis of the results of the research a proposal can be moved that silicon admixtures have clear influence on the improvement of water resistance of gypsum materials. The increase in strength against squeezing of the modified gypsum samples both in dry and water saturation state was noticed. On the other hand, the mass absorbability is decreasing. In the case of Ahydrosil K, strength against squeezing of the modified samples in a dry state increases up to 14,50 MPa and this is 9,02% more than the strength of the control samples.

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Mohamed Ahmad

Table 2: The influence of silicon resin admixtures on water resistance of gypsum materials

CAPILLARY ABSORPTION OF

WATER ADMIXTURE

STRENGTH MALACIA FACTOR

After hours

Rs Rsm Rz Rzm

Nm

1 3 6 24 %

W/B

MPa Ks Kz

% cm

0,5 14,50 7,40 5,70 2,51 0,51 0,44 5,11 1,0 1,4 2,0 3,1

1,0 14,15 6,79 5,25 2,52 0,48 0,48 4,31 0,9 1,3 1,7 1,9

1,5 13,69 6,30 4,98 2,54 0,46 0,51 3,54 0,8 1,3 1,3 1,4

2,0 13,02 5,04 4,37 2,40 0,42 0,55 2,74 0,6 0,9 1,2 1,3 Ahy

dros

il K

2,5

0,5

12,80 4,86 3,84 2,38 0,38 0,62 2,22 0,6 0,7 1,1 1,2 0,5 21,17 14,40 7,54 3,32 0,68 0,44 15,22 2,3 3,4 4,0 7,0 1,0 19,21 11,72 6,67 3,47 0,61 0,52 17,25 2,5 3,6 4,4 8,2 1,5 18,88 10,38 5,33 3,04 0,55 0,57 18,51 2,3 3,4 4,2 7,5 2,0 17,47 8,21 5,27 3,11 0,47 0,59 19,22 1,9 3,1 3,9 4,3

Sars

il H

-14/

R

2,5

0,5

14,22 5,83 4,39 2,68 0,41 0,61 20,51 1,0 1,5 2,5 3,0

The malacia factor during squeezing the modified samples amounts to 0,51 and is greater then the factor of the control samples by 70%. Mass absorbability decreases several times, compared to absorbability of the control samples and it amounts to 2,22%. The decrease in mass absorbability equals 81,07-91,78%.

Figure 1. The influence of silicon resin Ahydrosil K on water resistance of gypsum materials

3456789

101112131415

0,5 1,0 1,5 2,0 2,5

Percentage contribution of silicon resin Ahydrosil K

0,35

0,37

0,39

0,41

0,43

0,45

0,47

0,49

0,51

0,53

0,55

Ks

Rsm

Rs

Stre

ngth

aga

inst

sque

ezin

g in

dry

and

hum

id st

ate

[MPa

]

Mal

acia

fact

or d

urin

g sq

ueez

ing

In case of Sarsil H-14/R the obtained strength results are better than the results using Ahydrosil K, nevertheless the absorbability of the modified samples is greater. Strength in a dry state increases by 6,92-59,17%, and in full water saturation state it increases by 32,20-226,53%. The malacia factor during squeezing equals 0,41-0,68. The decrease in mass absorbability amounts to 24,04-43,63%. Silicon admixtures inhibit and stop capillary water absorption of the gypsum samples. In case of Ahydrosil K, the level of humidity of the samples does not exceed 3,1 cm after 24 hours of vertical alignment in water. The decrease of

52


absorbability of the gypsum samples modified with silicon admixtures and little capillary water absorption can be explained as follows: silicon polymers are one of the greatest hydrophobic materials. Thanks to their hydrophobic features, they are often used to increase water resistance of gypsum materials and other porous materials. As a result of alkylsiloxane molecule orientation on the border surface, gypsum - OH-Si group hydrophyte polymer directed towards gypsum undergoes strong attraction by ions situated on its surface, conditioning the layer adherence. Hydrophobic hydrocarbon groups directed outward determine strong hydrophobic features of the created membrane. Silicon resins cover the walls of porous gypsum materials with a hydrophobic layer (membrane) making them water non-permeable (non-moistening). After hardening the silicon layer on the walls of gypsum pores, their surface is very smooth what causes very low water adherence compared to the surface of gypsum crystals what as a consequence directly influences decrease in absorbability and capillary absorption of water. As a result of weak adherence, water does not fill the cavities of pore surfaces and does not show adherence towards the air located in the pores. This phenomenon is confirmed by the hypothesis that gypsum material moistening does not depend only on chemical gypsum and water characteristics but also on its surface microstructure.

Figure 2. The influence of silicon resin Sarsil H-14/R on water resistance of gypsum materials

5

7

9

11

13

15

17

19

21

23

0,5 1,0 1,5 2,0 2,5

Percentage contribution of silicon resin Sarsil H-14/R

0,38

0,42

0,46

0,50

0,54

0,58

0,62

0,66

0,70

Ks

Rsm Rs

Stre

ngth

aga

inst

sque

ezin

g in

dry

and

hum

id st

ate

[MPa

]

Mal

acia

fact

or d

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g sq

ueez

ing

6.2 The influence of acrylic resin admixtures on water resistance of gypsum materials

The results of the research concerning the influence of acrylic preparation Solakryl SW-100 on water resistance of gypsum materials are presented in table 3. The acrylic preparation, Solakryl SW-100 (trade name) in powder was used for the purpose of this research. This preparation is produced by Zakłady Azotowe “Kędzierzyn - Koźle”. The quantity of the used acrylic preparation amounted between 1,5-3,5% in relation to gypsum mass. As an inhibitor of time of combining the gypsum leaven, citric acid was used in the quantity of 0,04% in relation to gypsum mass. In order to harden the acrylic preparation Solakryl SW-100, initiators were used according to the manufacturer’s manual. These initiators were: triethanolamine (TEA) and ammonium persulfate (APS). The acrylic preparation Solakryl SW-100 was dosed directly with make-up water.

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Mohamed Ahmad

Table 3: The influence of acrylic resin admixtures on water resistance of gypsum materials


WATER ADMIXTURE STRENGTH MALACIA FACTOR

After hours

Rs Rsm Rz Rzm

Nm

1 3 6 24 %

W/B

MPa Ks Kz

% cm

1,5 24,31 10,70 7,90 2,53 0,44 0,32 12,89 0,5 1,0 1,5 2,5

2,0 25,30 12,14 9,15 3,11 0,48 0,34 11,20 0,4 0,8 1,0 2,3

2,5 27,21 13,88 10,59 3,81 0,51 0,36 9,01 0,3 0,5 0,9 2,0

3,0 29,31 - 5,21 - - - - 1,0 1,5 1,7 2,8 Sola

kryl

SW-1

00

3,5

0,5

33,24 - 3,51 - - - - 2,0 2,4 3,0 6,0

However, the quantity of the initiators from water solutions NA and APS, were adjusted to the general mass of the acrylic preparation Solakryl SW-100 dissolved in make-up water. On the basis of the research results, it can be concluded that acrylic preparation Solakryl SW-100 has plasticizing effects because while increasing its dosage to water, the gypsum mass became more liquid, plastic and easily workable. The preparation Solakryl SW-100 inhibits the beginning and ending of the combining of the gypsum leaven. During trabecula deformation, they showed great adherence to the form walls. Norm trabeculas 4x4x16 cm after taking out of the forms were plastic. Together with the increase in Solakryl SW-100 participation, the volumetric consistency of the gypsum samples in dry state increased as well. Basing on the results of the research, it can be concluded that the preparation Solakryl SW-100 increases strength of the modified gypsum samples both in a dry state and in full water saturation state. The increase of the strength is conditioned by the percentage quantity of the preparation in gypsum leaven. Strength of the gypsum samples modified with Solakryl SW-100 kept increasing until the contribution of Solakryl SW-100 in leaven exceeded 2,5% of the weight. Then, the great decrease in strength was observed. Strength against squeezing of the gypsum samples in dry state reached 24,31-33,24 MPa and this equals to 82,78-149,92% in relation to control samples. In full water saturation state, strength increased by 142,63-214,74% in comparison with control samples. Modified gypsum samples containing more than 2,5% of weight after emerging in water showed big swelling what resulted in destruction of their structure and it was impossible to mark their strength features. On the surfaces of these samples, big white rashes appeared.

7 The influence of silicon and acrylic resin admixtures on water resistance of gypsum materials.

Increasing hydrophobic and water resistance features of gypsum materials is a basic and major condition for their application in building industry. This aim is very difficult to obtain and a lot of scientists, researchers, institutions and other units dealing with such issues work on this subject. The obtained results of the researches concerning the influence of chemical admixtures individually introduced to gypsum leavens motivated us to continue laboratory research over increasing hydrophobic and water resistance features of gypsum materials. Most

54


of the chemical admixtures improve one or several features while at the same time deteriorating other features. Introducing chemical admixtures comprehensively to gypsum leavens was aimed at improving both their strength features and hydrophobic features. The results of the research concerning the influence of chemical comprehensive admixtures of silicon resin Sarsil H-14/R and acrylic resis Solakryl SW-100 on hydrophobic and water resistance features of gypsum materials are presented in table 4 and shown in Figure 3. In accordance with the results obtained it can be concluded that the best results as far as hydrophobic and water resistance features are concerned were obtained during simultaneous introduction of these chemical admixtures to the gypsum leaven. Strength against squeezing of the modified gypsum samples in dry state amounts to 22,64-26,41 MPa, on the other hand, in full water saturation state it equals 14,31-19,59 MPa.

Table 4: The influence of silicon and acrylic resin admixtureson water resistance of gypsum materials


WATER ADMIXTURE STRENGTH MALACIA FACTOR

After hours Solakryl SW-100

Sarsil H-14/R Rs Rsm Rz Rzm

Nm

1 3 6 24

%

W/B

MPa Ks Kz

% cm

1,5 0,5 22,64 14,31 7,54 2,50 0,63 0,33 13,21 0,3 0,4 0,8 1,0

2,0 0,5 23,51 15,43 8,34 2,98 0,66 0,36 12,37 0,2 0,3 0,6 0,8

2,5 0,5 24,18 16,58 9,58 4,00 0,69 0,42 11,89 0,1 0,1 0,0 0,0

3,0 0,5 25,38 18,21 10,34 4,89 0,72 0,47 11,21 1,2 1,3 1,5 2,1

3,5 0,5

0,5

26,41 19,59 11,27 5,85 0,74 0,52 10,89 1,3 1,5 1,7 3,2

This strength is higher than strength of the control samples by 224,49-344,22%. The malacia factor during squeezing equals 0,63-0,74 and is greater than the malacia factor of the control samples by 110,00-146,67%. The decrease of the weight absorbability amounts to 51,07-59,67%.

Figure 3. The influence of silicon and acrylic resin admixtures on water resistance of gypsum materials

13

15

17

19

21

23

25

27

1,5 2,0 2,5 3,0 3,5

Percentage contribution of resin Solakryl SW-100 at 0,5% of Sarsil H-14/R

0,50

0,55

0,60

0,65

0,70

0,75

0,80

Ks

Rsm

Rs

Stre

ngth

aga

inst

sque

ezin

g in

dry

and

hum

id st

ate

[MPa

]

Mal

acia

fact

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ing

55

Mohamed Ahmad

8 Conclusion

The conducted laboratory researches showed that the improvement of gypsum materials technical features through implementing organic chemical admixtures to gypsum leavens is the most effective way of modifying the strength and hydrophobic features of gypsum materials. Silicon resins chemical admixtures Ahydrosil K and Sarsil H-14/R have positive influence on strength and hydrophobic features of gypsum materials. However, while increasing the content of admixtures in them, the value of malacia factor of modified gypsum samples during squeezing and bending decreases. Better results were obtained by using acrylic resin admixture Solakryl SW-100. Whereas, the best strength and hydrophobic effects were gained by implementing complex silicon resin Sarsil H-14/R and acrylic resin Solakryl SW-100 admixtures to gypsum leavens. Combined chemical admixtures implemented simultaneously to gypsum leavens influence the technical features of modified gypsum materials in various directions increasing their hydrophobic and water-proof features.

References

[1] Ahmad M., The influence of artificial resins on water resistance of gypsum materials. Exercise books of scientific Rzeszow University of Technology. Civil and environmental engineering. 2009.

[2] Ahmad M., Influence of melamine-formaldehyde resins additives and other combined materials on water resistance of gypsum materials. PhD thesis. Cracow, 1994.

[3] Akerman K., Zawada E. Gypsum. ESL, Common Knowledge. Warsaw, 1951. [4] Kowalski Z., Plastic coatings. WNT, Warsaw 1973. [5] Kucharska L., Moczko M., Effect of sulfur and polyethylene on the material properties

of hot pressed plaster. Building Materials, 1987, No. 1, 16-17. [6] Mlynarczyk E., Bending pieces of wood, glass-reinforced polyester laminate. PhD

thesis. Cracow, 1989. [7] Osiecka E., Gypsum Building Materials - past and present. Cement Concrete Lime, No.

5, 2002. [8] PN-B-04360:1986 Adhesive plaster. Test methods. Physical and strength features

marking. [9] PN-B-04500:1985 Building mortars. Research on physical and strength features. [10] Experimental Plant Brochures silicones, Nowa Sarzyna, Industrial Chemistry Research

Institute. Warsaw 1993. [11] Saechtling H., Zebrowski W., Plastics, guide. WNT, Warsaw 1978. [12] Skalmowski W., Chemistry of building materials. Arkady, Warsaw 1971. [13] Skalmowski W., Building materials technology, vol third. Arkady, Warsaw 1968.

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The load-carrying capacity of the eccentrically-compressed reinforced-concrete columns strengthened with loading

Zinoviy Blikharskyy, Evgen Tsariov, Roman Khmil

Lviv Polytechnic National University, UKRAINE, Building construction and bridges department,

e-mail: [email protected]; [email protected]; [email protected]

Abstract

This article deals with the methodology of experimental researches of the eccentrically-compressed reinforced-concrete elements strengthened with loading. The characteristics of the prototypes stand for testing and measuring devices are described. The research has been carried out by testing two series of reinforced-concrete columns 2200х140х180 mm of size under the action of the short-term loading. Reinforcement of specimens is symmetric with the longitudinal armature of А400С Ø12 mm class. Descriptions of experimental columns are presented in table. At the second stage of research two reinforced columns were tested under loading of 30% of the maximum expected. In the process of testing the destruction of columns passed fluently. Cracks 0.05 mm arose at loadings of 30-40 кN, approaching approximately 25% from the destructive one. Considerable opening of cracks 0.2-0.3 mm as well as increase of bendings was observed at 100-110 кN, and physical destruction passed at 164.8 and 160.9 кN. The strengthened columns had physical destruction at 235-247 кN. On the basis of experimental data the graphs of deflections, deformations of the stretched armature and compressed concrete were built. As the destructive loading for two specimens the average value, namely 141 кN, was accepted. The ultimate loading of strengthened columns was graphically obtained at 181,5 кN As a result of the conducted research there has been approved the method of experimental research of the compressed reinforced-concrete elements under the action of the short-term loading, enclosed with an eccentricity, as well as there has been revealed that the method of calculation allows to determine the strength of the eccentrically compressed columns (EC) with satisfactory convergency and reinforced columns (RC) with not satisfactory convergency .

Key words: methodology, research, eccentrically-compressed, reinforced concrete, strengthened with loading.

1 Introduction

There columns are the one of the basic carrying part of all buildings. They usually have a considerable reserve of bearing capacity, since they are designed taking into account the most

57

Zinoviy Blikharskyy, Evgen Tsariov and Roman Khmil

disadvantageous combination of loadings the simultaneous action of which is of low possibility. However in the process of their exploitation there arises necessity in columns strengthening. It is related to the mistakes at design and building, improper exploitation, the increasing of loading at a reconstruction, etc. Consequently there is a necessity of estimation of bearing capacity, firmness and deformability of reinforced-concrete columns and methods of calculation of the strengthened constructions.

For today the amount of works devoted to research of the eccentric compressed elements, in particular increased at the action of loading, is insignificant. Therefore there is a necessity to continue researches in this direction and obtain more experimental results.

The grounds of choice of methods of strengthening and methods of calculation are presented in papers of many researchers [1-7]. The strengthening holders are the separate issue in researches, since they are the cheapest and the most technological in the production process. Mainly all proposals in relation to the calculation are based on the method of ultimate equilibrium, nevertheless not enough attention is paid to the firmness and deformability of constructions. The experimental researches of the eccentric compressed elements increased by concrete holders, especially at the action of loading, are practically absent.

2 Results of researches

For the holding of experimental researches there were made 4 reinforced-concrete columns from two experimental series. The first series are exemplary columns without strengthening (EC-1.1 and EC-1.2) tested on the eccentric pressure. The second series are columns, which were strengthened by the concrete holder at the action of loading which was 30% from the destructive load of 1-t series columns (RCc-2.1-0.3 and RCc-2.2-0.3).

The experimental specimens of reinforced-concrete columns are 2200 mm long, 140 mm wide and 180 mm high with console for the transferring of load with eccentricity. Columns reinforcement is symmetric with the longitudinal armature ∅12mm A400C. Concrete mix was accepted with the proportion of components Cement/Sand/Stone=1/1,16/2,5 at the water/cement relation of 0,375. A concrete holder was accepted in 30 mm thickness on all of the column length. The concrete holder mix was accepted with the proportion of components of Cement/Sand/Stone=1/1,26/2,42 at the water/cement relation of 0,35.

At determining the strength characteristics of materials there has been received that the limit of armature yield stress was σy=590 MPa, the average prism concrete strength of columns was Rb=38,7 MPa, the average prism concrete strength of holder was Rb,ad = 45.4 MPa.

Columns were tested on the special facilities by the hydraulic jack. The construction of facilities foresaw the test of specimens on pressure with the joint of fixing in horizontal position. Loadings were applied by the single force with the eccentricity е=150 mm on the console of column. Loadings were put by steps of N=0.05Nmax with 12 min exposure time after each step. Data from devices were taken twice – at once after loading and at the end of the exposure time.

The force values were controlled by the exemplary manometer, that was calibrated together with the pumping station and jack before testing and after it. Deformations of concrete were measured in three sections by 18-th (for the series of EC) and 34 (for the series of RC)

58


indicators of 0,001 mm scale. Deformations of armature were measured by 12 indicators disposed at a special fixing welded to the armature in a way to avoid contact with concrete. Indicators were disposed with a 200 mm base in relation to experimental sections on 25 mm height from the surface of the concrete holder. Deflection of columns was measured by 7 indicators with 0,01 mm scale (for the series of EC) and by 5 indicators (for the series of RC) which were disposed on the less compressed columns edge with similar steps. In the process of testing there has also been conducted visual control after the moment of cracks formation, cracks width and their development by the microscope MPB-2M with 0.05mm scale.

The general view of reinforced-concrete column of series of EC and RC in a special facility is presented on Fig.1.

a)

b)

Figure 1: A general view of experimental column of EC (a) and RC (b) series

Destruction of columns EC-1.1 and EC-1.2 passed fluently. Cracks 0.05 mm arose up at loadings of 30-40 кN, that were approximately 25% from the failure loading. Considerable cracks 0.2…0.3 mm wide as well as the increase of deflection were observed at 100-110 кN. The physical failure passed at 164.8 and 160.9 кN. On the basis of the obtained results the graphic curves of deformations of the stretched armature and compressed concrete depending on loading are built. We graphically obtained the value of loading at which destruction of

59


columns took place by fluidity of armature with the next physical destruction of the compressed concrete. For the failure loading is accepted the average value of two specimens graphically determined, namely 141 кN. The general view of the tested columns specimens is given on Fig.2.

Figure 2: General view of the tested columns from top to bottom: EC-1.1, EC-1.2, RC-2.3-0,3 and RC-2.4-0,3

The testing of reinforced-concrete columns, reinforced at the action of loading, was conditionally divided into 2 stages. The 1-st stage (before strengthening) includes the preparation of specimens, leading to loading of a necessary level and implementation of strengthening at the action of loading. On the 2-nd stage (after strengthening) there are set measuring devices and a column is tested to the physical destruction.

On the I-st stage the surface of column concrete was carefully cleared up from laitance by the abrasive circle. To improve the adhesion of “new” and “old” concretes special notches were executed. For measurement of “old” concretes deformations to the surface of column the special metallic holders were glued with a 200 mm base. Then there was arranged a stocking carcass from the steel wire of ∅1,2 mm (four longitudinal bars and transversal loops with a step 60 mm). A ready column was set in the project position and centered at loading N=0.1Nmax, whereupon there were finally fixed supporting hinges by the cement-sandy mix.

On the 2-nd stage after 28 days of concretes hardening of holder the columns were tested by short-time loading. At loading to 70-80 кN practically no increases of deflection and deformations are fixed. Beginning from 100 кN we observed the increase of deformations of armature and «new» and «old» concretes. At value of loading 235 and 247 кN the physical destruction of columns took place. It was accompanied by the considerable increase of deformations and deflections. Cracks to loading of 180 кN were within the limits of 0.05…0.3 mm and only on the last stages took place their considerable opening to 5 mm.

On the basis of the experimental data graphic curves of maximal deflections, deformations of the stretched armature and compressed concrete of column depending on loading are built. Also the comparison of bearing capacity with theoretical values, obtained according to the calculation by Ukrainian norms SNiP 2.03.01-84* [8], is conducted The curves of maximal

60


deflections are shown on fig.3, deformations of stretched armature on Fig. 4 and deformations of compressed concrete depending on loading on Fig. 5 correspondingly.

Figure 3: Maximal deflection of columns.

Figure 4: Deformations of stretched armature.

Figure 5: Deformations of the compressed concrete.

The data of experimental and theoretical researches are presented in table 1. At calculation of the increased section by Ukrainian norms SNiP 2.03.01-84*, there has been considered that

61


the increased section was solid with the given physical and mechanical characteristics of «new» and «old» concretes.

Table 1: Bearing capacity of reinforced-concrete columns

Experimental value Theoretical value Code column Physical destruction

Nf.exp, кN Bearing capacity

Nu.exp, кN By SNiP 2.03.01-84*

Nu.norm, кN

Nu.exp/ Nu.norm

EC-1.1 164.8 142.6 139.1 1.03 EC-1.2 160.9 139.9 139.5 1.01

RC-2.1-0,3 235.0 181.2 250.6 0.72 RC-2.2-0,3 247.0 182.0 251.3 0.73

3 Conclusions

Experimental researches of the eccentric compressed columns, including those reinforced at the action of loading, have been conducted. The comparison of experimental bearing capacity of columns with the theoretical values, obtained after calculation according to Ukrainian norms SNiP 2.03.01-84*, has been conducted. It has been set that the method of calculation of the eccentric compressed reinforced-concrete elements according to SNiP 2.03.01-84* gives a satisfactory convergence, however the stocked bearing capacity is only up to 3%. For the calculation of the eccentric compressed columns reinforced by concrete holder the method of SNiP 2.03.01-84* gives the considerable overstating of results up to 28% in comparison with the experimental data.

[1] References

[2] Blikharskiy Z.Ya. Reconstruction and strengthening of buildings and constructions. – Lviv: «Lviv Polytechnic National University», 2008. – 108 p. (in Ukraine).

[3] Golyshev A.B., Krivosheev p.I., Kozeleckiy p.M. and others; edited by Golysheva A.B. Calculation and technical solutions of strengthening of the reinforced concrete constructions of the manufacture plants and bases subsidence. Kiev: LOGOS, 2008. – 304 p. (in Russian).

[4] Mal'ganov a.I., Plevkov B.C., Polischuk a.I. Reconstruction and strengthening of building constructions of accidental reconstructed buildings. – Tomsk, 1990. - 316 p. (in Russian).

[5] S.V. Bondarenko, R.S. Sanzharovskiy. Strengthening of the reinforced concrete constructions at reconstruction // Stroyizdat. – Moscow, 1990. - 352 p. (in Russian).

[6] A.L. Shagin, Yu.V.Bondarenko, D.F. Goncharenko, V.B. Goncharov. Reconstruction of buildings and constructions. - Moscow, 1991. – 351p. (in Russian).

[7] N.M. Onufriev. Strengthening of the reinforced concrete constructions of the manufacture plants and constructions. - Moscow, 1965. – 340 p. (in Russian).

[8] E.R. Khilo, B.S. Popovich Strengthening of the reinforced concrete constructions at changing of the calculation scheme of the stressed state. - Lvov, 1976. -145 p.(in Russian).

[1] SNiP 2.03.01-84*. Concrete and reinforced concrete structures. - Moscow: USSR TSITP Gosstroya SSSR, 1989. – 80p. (in Russian).

62


Experimental tests of steel column to concrete wall connection

Lucjan Janas, Aleksander Kozłowski, Rafał Klich

Rzeszów University of Technology Faculty of Civil and Environmental Engineering

e-mail: [email protected], [email protected], [email protected]

Abstract

In top roof extension of existing buildings there is often a need to connect steel columns of new bearing structure to existing, old concrete walls. To investigate behavior of such connections, experimental tests were conducted. Two frames in natural scale were investigated: Frame F-1: columns of HEA200, beams IPE3000, two anchors in column bases, Frame F-2: columns IPE270, beams IPE300, four anchors in column bases. Height of the frames was 3,0 m, span 4,2 m. Frames were supported on the concrete walls made from concrete C16/20, what might simulate “old concrete wall”. Experimental tests were conducted in the Laboratory of Faculty of Civil and Environmental Engineering, Rzeszow University of Technology, Rzeszow, Poland.

Key words: steel column, concrete wall, column base connection

1 Introduction

In many European cities, because of the lack of available land and economic reasons, there is a need to extend and adapt existing buildings to meet new social and functional demands. Horizontal or vertical extension can be adopt to create a new habitable space, while vertical extensions are more common and often used in city centres. Vertical or roof-top extensions create particular requirements, as a full understanding of the structural capabilities of the existing building, including foundation, and of the connection between the new and existing structure. Type of these connection depends on the structural system applied to top roof extension. If the existing structure is made of masonry walls, the roof-top extension should be constructed from light steel framed wall panels. To connect these panels to the existing wall, a continuous connection in the form of a U-track is required. In case of framed steel structures used as structural system, typical column bases can be adopted, but with the following restriction: - supporting concrete base is often in the form of narrow concrete walls, as in prefabricated buildings, - concrete condition is rather poor after many years of exploitation, - point loading is applied to concrete wall.

63

Lucjan Janas, Aleksander Kozłowski and Rafał Klich

In order to validate the expected behaviour of the connection between a new steel frame and the existing building structure, a series of tests was carried out at the Rzeszow University of Technology, in the Laboratory of Faculty of Civil and Environmental Engineering [1].

2 Description of samples

Two frames, namely F-1 and F-2 were investigated. Frames were supported on the concrete walls made from concrete C16/20, what might simulate “old concrete wall”. Test set-up consists of heavy test rig frame, to which two oil Instron-Schenck jacks of capacity 630 kN were connected by steel rods. Vertical loading was applied in the column axis through heavy steel beam (Fig. 1, 2).

Figure 1: Frame F-1 on test rig; 1 - tested frame F-1, 2 - concrete wall (foundation), 3 - investigated connection, 4 - test rig, 5 - column to apply horizontal force H, 6 - oil jack 630kN, 7 - steel rods, 8 - heavy beam to apply vertical forces V

Frame F-1 was made of steel S355JR, columns of HEA200, beams IPE300. Beam to column connection was designed as welded fully rigid, with stiffeners. Frame consists of two parts, connected in the symmetry axis by four bolts M24 grade 10.9. Column bases consist of base plate of dimensions: 20x220x230. Two holes φ22 for anchors was predicted in the middle of plate (Fig. 3a).

Frame F-2 was made of steel S355JR, columns of IPE270, beams IPE300. Beam to column connection was designed as fully rigid, welded with stiffeners. Column bases consist of base plate of dimensions: 20x165x300. Four holes φ22 for anchors was predicted in the middle of plate (Fig. 3b).

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Figure 2: Frame F-2 on test rig

Figure 3: Column base: a) Frame F-1, b) Frame F-2

3 Concrete walls and anchors

Walls were designed from concrete grade C16/20. Thickness of wall is 20 cm, height is 80 cm. Wall base is 40 cm wide and 40 cm high. Reinforcement of foundation is made of #12 steel bars and stirrups of BSt500S steel grade. General view of foundation is shown in Fig. 4a. Holes were predicted in concrete foundation (Fig. 4b) to connect them to power floor.

a) b)

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Figure 4: View of foundation (a) and connection to power floor (b)

During concreting cubic specimen 150x150x150mm were collected to investigate concrete strength. The 28 days after concreting, compression strength tests were executed and mean value of concrete strength of 20 MPa was obtained.

To connect frame with foundation steel φ20mm bonded anchors were used (HIT-HY 150 MAX produced by HILTI). Anchors were fixed by epoxy resin; the anchorage length is equal to 170 mm. The assembly of anchors is showed in Fig. 5 illustrates detail of anchor fixing. Columns of F-1 frame were connected by means of two anchors each, and columns of F-2 frame by means of four anchors each.

Figure 5: Filling of hole by resin and fixing of anchors

a) b)

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Spaces under base plate were grouted. Grouting layer was 20 mm thick and was made of self-compacting grout SikaGrout-4N, produced by Sika (Fig. 6). After one-day period of bonding in temperature +20oC, it gets characteristic compressive strength 25-30MPa.

Figure 6: Pouring of grouting layer and view to the grouted base plate

4 Instrumentation

During the test, following equipment was used: – static and dynamic loading system Instron-Schenck, to apply vertical forces V, – steel rod with dynamometer, to apply horizontal force H, – Spider and Catman computer systems to collect and record measured data, using linear

variable displacement transducers (LVDT), strain gauges and inclinometers.

Diagram showing points of loads application and diagram illustrating arrangement of LVDT-s is shown in Fig. 7. Arrangement of strain gauges and inclinometers is presented in Fig. 8.

Figure 7: Points of applying loads (a) and arrangement of LVDT-s (b)

a) b)

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Figure 8. Arrangement of strain gauges (a) and inclinometers (b)

By means of LVDT-s (represented by symbols from 1 to 3 and 5 to 10 in Fig. 7b) displacements and angles of rotation of most important parts of frames were measured. Inclinometers (represented by symbols O1 to O4 in Fig. 8b) were used to obtain data to verification of measurements obtained from LVDT-s. Stresses developed by loading were measured by strain gauges (marked T1 to T12 in Fig. 8a).

5 Loading procedure

First, vertical load V + 100 kN was applied in line of each column axes, using oil jacks, steel rods and heavy beam, to cancel slacks and gaps and to test loading equipment. After unloading to “0”, compression force in each column was applied of value equal to 270 kN. Next, horizontal load H was applied in the level of upper beam of frame. Horizontal load was slowly increased, in displacement control manner, up to collapse of frame foundations joints. For frame F-1 unloading from 86 to 70 kN, while for frame F-2 unloading from 110 to “0” were predicted. The full loading procedure is shown in Table 1.

Table 1: Loading procedure Frame F-1 Frame F-2

V [kN] H [kN] V [kN] H [kN] 0 0 0 0

100 0 100 0 0 0 0 0

270 0 270 0 270 86 270 110 270 70 270 0 270 100 (max.) 270 157 (max.) 270 0 270 0

0 0 0 0

a) b)

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6 Tests results

6.1 Frame F–1

Moments in connection were calculated on the basis of strain gauges readings, with taking into account current values of vertical force. Rotations of the left and right connection were calculated using readings of relevant LVDT-s, subtracting rotation of concrete wall. More test results can be found in reports [1] and [2].

The main results for frame F-1 obtained from tests are:

- relation between horizontal load H and global frame drift (horizontal displacement of upper beam of frame), Fig. 9,

- relation between connection moment and angle of rotation of base plate connections, separately for left and right joint, Fig. 10,

- relation of horizontal load H and horizontal displacement of base plate in each (left and right) joint, Fig. 11.

0

20

40

60

80

100

120

0 10 20 30 40 50 60

H [kN]

Δ gl [mm]

H‐Δgl

Figure 9: Relation between horizontal load H and horizontal displacement of upper beam of frame

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‐5

0

5

10

15

20

25

30

0 5 10 15 20 25

M [kNm]

φ [rad*E‐3]

M‐φ

connect‐left

connect‐right

Figure 10: Relation between connection moment and angle of rotation of base plate

0

20

40

60

80

100

120

‐0,5 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0

H [kN]

Δ c [mm]

H‐Δc

Δc‐L

Δc‐R

Figure 11: Relation of horizontal load H and horizontal displacement of base plate

Failure modes:

- on the right side (Fig. 12) there was observed concrete wall cracking followed by conical shape shear cutting through the full thickness of the wall,

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- in the left joint, first separation of base plate from grout was observed in the tension side, then cracking of the wall starting from the middle of the wall and taking shape of the cone (Fig. 13).

Figure 12: Failure mode of the right connection

Figure 13: Failure mode of the left connection

6.2 Frame F–2

The main results of frame F-2 tests are: - relation between horizontal load H and horizontal displacement of upper beam of

frame, Fig. 14,

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- relation between moment in connection and angle of rotation of base plate connections, separately for left and right joint, Fig. 15,

- relation of horizontal load H and horizontal displacement of base plate in each (left and right) joint, Fig. 16.

‐20

0

20

40

60

80

100

120

140

160

180

0 10 20 30 40 50 60 70

H [kN]

Δ gl [mm]

H‐Δgl

Figure 14: Relation between horizontal load H and displacement of upper beam of frame

‐20

‐10

0

10

20

30

40

50

60

‐5 0 5 10 15 20 25 30 35 40

M [kNm]

φ [rad*E‐3]

M‐φ

connect‐left

connect‐right

Figure 15: Relation between bending moment and angle of rotation of base plate connections

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‐20

0

20

40

60

80

100

120

140

160

180

‐0,5 0,0 0,5 1,0 1,5 2,0 2,5 3,0

H [kN]

Δ c [mm]

H‐Δc

Δc‐L

Δc‐R

Figure 16: Relation of horizontal load H and horizontal displacement of base

Failure modes: - right joint: crashing of the concrete was observed on the compression side (Fig. 17), - left joint: main destruction was observed on the tension side (Fig. 18), on the

compression side only grout cracking was noticed.

Figure 17: Failure mode of the right connection – tension side (a) and compression side (b)

a) b)

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Figure 18: Failure mode of the left connection – tension side.

7 Conclusion

The test of pinned connection (frame F–1) was stopped at a shear load of 100 kN, which is considerably in excess of the horizontal wind loads that would be expected in a one or two storey top roof extension. The movement of the concrete wall was 4.5 mm at this load and the displacement of the frame was approximately 50 mm. It is apparent that a small moment is generated at the base of the frame, even if designed as pinned. The tests of the semi-rigid connection (frame F–2) were continued to a shear load of 160 kN, at which point the horizontal displacement of the frame was 60 mm. At a load of 100 kN , the displacement was 60% of that of the pinned test. The bending moment diagram at this load shows that the moment in the column was reduced by 30% and the moment at the base was 60% of that in the frame, which indicated a high degree of base fixity (although not fully fixed). There is a large difference between values of moment in connections between the pinned (14.1 kNm) and semi-rigid connection (45.6 kNm) cases. The failure mode was in the concrete by crushing of the concrete on the compression side, together with cracking of concrete wall on the tension side.

Acknowledgements

Tests were carried out within the grant “Renovation of buildings using steel technologies” (ROBUST) RFSR-CT-2007-0043 financed by the Research Fund for Coal and Steel. Equipment used in tests were purchased in the project No POPW.01.03.00-18-012/09 from the Structural Funds, The Development of Eastern Poland Operational Programme cofinanced by the European Union, the European Regional Development Fund.

References [1] KOZLOWSKI A, JANAS J., et. al. Investigation of attachment of new floors, roofs and

building extensions using steel including second order effects, tolerances, wind loading. WP. 3.3 Individual activity report to RFSR-CT-2007-0043. Rzeszow University of Technology, 2010.

[2] RENOVATION OF BUILDINGS USING STEEL TECHNOLOGIES (ROBUST) RFSR-CT-2007-0043. Final report, 2010.

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Nondestructive tests of laboratory models based on elastic waves measurements and artificial neural networks

Piotr Nazarko, Michał Jurek, Leonard Ziemiański

Rzeszow University of Technology Faculty of Civil and Environmental Engineering, Department of Structural Mechanics

e-mails: {pnazarko, mjurek, ziele}@prz.edu.pl

Abstract

The paper presents some resent results of damage tests performed on laboratory models made of various materials. A nondestructive technique of elastic wave propagation and the technology of piezoelectric transducers were used in this approach. For the purpose of signal analysis, advance signal processing techniques and artificial neural networks were used. In the consequence a structure diagnosis and health monitoring system was developed and two levels of the damage identification problem were realized: novelty detection and damage assessment. The system's accuracy and reliability were verified during laboratory tests of strip specimens made of various materials. Preliminary results of investigations performed on a steel plate specimen were also discussed. It was proved that the system can be used for the analysis of simple as well as complex signals. Moreover, the system can be fully integrated into the monitored structure and can operate on-line as an automatic Structural Health Monitoring system.

Key words: structural health monitoring, nondestructive tests, elastic waves, signal processing, artificial neural networks

1 Introduction

Structural health monitoring (SHM) systems, identify with damage detection, become a very important part of a structure which can improve its safety and reliability. SHM systems are designed to conduct periodical or continuous inspections and to detect abnormal conditions, mainly a damage location, extent and remain time of safety usage. Developments of such systems involved also an enhancement search of nondestructive techniques suitable for on-line monitoring and which make integration with a structure possible.

Beyond the mentioned safety reasons of equip the structure with SHM system, equally important for management staffs are: decreased time and cost of inspection, increased inspection access and structure’s efficiency, repair planning when really needed, absence of periodical rejection structure from usage.

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Piotr Nazarko, Michał Jurek and Leonard Ziemiański

In the present paper some basic ideas of the SHM system functioning are provided and supported by a set of preliminary tests performed on laboratory specimens made of various materials. Thanks to application soft computing methods [1] two levels of damage identification were executed (anomaly detection, prediction of damage size) and are discussed with respect to selected examples. In addition some recent results of investigations performed on geometrically more complex specimens (steel plate) and the proposed identification algorithm were discussed.

2 Elastic waves in structure diagnostics

A nondestructive technique that is suitable for SHM systems utilizes the phenomenon of elastic wave propagation in solids [2-5]. The monitored structure is usually equipped with piezoelectric transducers which are used for the purpose of wave excitation and sensing. It can be done during its construction or an inspection, so that control points can be set up in areas that are hidden or inaccessible for most NDT techniques.

Analysis of elastic wave signals consists in general of quantitative and qualitative descriptions of their changes (e.g. attenuation, distortion, reflection) caused by damage appearance and growth. The principle governing the use of the elastic wave propagation phenomenon rests on the assumption that any obstacles will cause wave reflections and affect theirs transition through a damaged area (Fig. 1). The signals received can be subjected to a procedure which pinpoints the location of the disturbance and predicts its nature and extent.

Figure 1: An idea of elastic waves utilization for structure diagnosis

An operating frequency of excitation signal is usually tuned in order to trigger propagation of selected waveform (mostly A0 or S0) [6]. One reason of this action is sensitivity of certain elastic wave forms for changes due to an expected type of damage [7]. However, a very important issue remains clarity of the signal to be analyzed since a large majority of known approaches deal only with impulse-echo signals where excitation wave package and occurring reflections from a model boundaries (or existing damage) are well distract and visible enough to be recognized. Unfortunately measurements conducted on a real structure or in service conditions may lead to quite complex signals, useless for mentioned techniques and consequently damage detection.

The first stage of a signal processing algorithm utilizes usually denoising procedure which may be composed of wavelet transformation and digital filtering. Then computed parameters,

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such as wave amplitudes, spectral densities, correlation factors, principal components etc., can be used for training the diagnosis system.

3 Artificial neural networks in damage identification

Beyond the sensor level and signal processing, the next two stages of SHM system involve identification of structure state and prediction of damage parameters. Soft computing methods and computed signal parameters were used to solve this problem.

First Auto-associative NNs were studied for the purpose of novelty detection. In case such trained network is fed with the inputs obtained from a damage state of the system, the novelty index NI(x) = ||x – x’||, which is defined as the Euclidean distance between the target outputs x and the outputs of the NN x’ will increase [8]. If the learning was successful, the index will be NI(x) ≈ 0 for data obtained from undamaged state. However, if data is obtained from the damaged system, the novelty index will indicate an abnormal condition providing a value strongly different to zero. In this task the ANN were trained with the input vector x and the output vector x’ defined as follows x (16×1) = { ci , i=1, ..., 16} → x’ (16×1) = { c’i , i=1, ..., 16} (1)

where c are the principal components computed from the measured signal [9].

Second alternative solution studied utilizes Support Vector Machines Binary Decision Tree (SVM BDT) [10, 11]. The example investigated consists of 4 labels related to specimen’s condition (undamaged, damaged 1, damaged 2, damaged 3) and for each one instance classes were assigned as follows: 0, 1, 2, 3. Then, the classes were organized in clusters since there are two outputs only at each level of BDT (Fig. 2). At first stage a structure can be classified as undamaged (0) or damaged (1, 2, 3). Next the damage patterns (1, 2, 3) can be split to those related to the specimen with one damage (1) and more than one damages (2, 3). Finally, the specimen with two and three damages can be identified at the last stage. In this task the SVM NN was also trained using the computed principal components while at each level the respective input and out vectors were defined as follows x (16×1) = { ci , i=1, ..., 16} → y (1×1) = {l; l=0 or 1}. (2)

Figure 2: SVM Binary Decision Tree

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In case the damage level has been determined a NN designed for damage parameters prediction can be used. In such the way a damage parameters can be evaluated. A standard feed-forward NN was trained with the input and output vectors defined as x(3x1) = {mi; i=1, 2, 3} → y(2x1) = {b, h} (3)

where m is a vector of computed spectrum magnitudes, while b and h refer to the predicted damage width and height given in millimeters.

4 Laboratory tests and results of damage identification

4.1 Strip specimens made of various materials

The proposed approach of NDT was studied for few laboratory strip specimens made of various materials: aluminum, steel and Plexiglas [12]. In general, the investigated models may be divided into two categories, where reflections from existing obstacles (e.g. damage areas, model limits) are well separable, and those which are pretty complex or even non-separable. Analysis of the first group of signals is rather clear and simply, while in case of short models, equipment limitations, low frequency excitations, noise existence it becomes a very hard problem.

An investigated aluminum strip (2000x10x1 mm) is the example where the recorded elastic wave signals are rather simple for visual analysis. In particular, it can be found on the time signal histories that the introduced excitation, reflection from the strip end and additional reflections (between the excitation and the first pass reflections) related with respective damages are well indicated. An analysis of the reflection arrival time and theirs amplitudes can be used for damage detection and evaluation problem. Since the elastic wave signals measured on the strips made of steel and Plexiglas are more complex whereas the obtained accuracy is on the same level, the results of novelty detection and damage parameter’s prediction are discussed following the second example.

Thus, let us consider a specimen steel strip (808x32x2 mm) where damages were introduced by notching across the width of the specimen for 20 mm from an outer edge to the opposite one (Fig. 3). Two piezoelectric transducers served as actuators and sensors of elastic waves. Time signals measured at the actuator position for selected extents of damage are shown in Fig. 4. Unfortunately the disturbances introduced by damage are visually undetectable so that all the runs appear identical. In addition most of the procedures described in the literature refer to analysis of much simpler signals [2, 6]. Nevertheless it was proved that the system established for elastic waves analysis can detect the damage presence and predict its size with a reasonably well accuracy.

Figure 3: An investigated steel strip specimen with location of PZT transducers and damages

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Figure 4: Elastic wave signals recorded in the steel strip (excitation by 6 sine waves, 50 kHz)

The obtained results of novelty detection have shown that two-level (undamaged, damaged) patterns classification was done perfectly. However, in case of multilevel classification (undamaged, 1 damage, 2 damages, etc.) an error arose after separation to indirect damage classes (see Fig. 5 and Table 1).

Figure 5: Results of novelty detection performed on steel strip

Table 1: Confusion matrix obtained for multilevel classification of steel strip: NN testing (16-5-16)

True Predicted classes classes undamaged damage 1 damage 2

undamaged 100% 0% 0% damage 1 0% 89,0% 11,0% damage 2 0% 0% 100%

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The finally obtained results followed many repetitions of NN training with various input vectors related to the extracted wave parameters, type of excitation signal (continuous, impulse), frequencies, location of control points, etc. Testing accuracy for the steel strip varied between 0.10 and 1.13 mm. Fig. 6 shows both the target and the predicted (by the trained NN) values of damage parameters as well as interpretation of one exemplary results obtained for testing pattern.

Figure 6: Damage size predicted by the trained NN in the steel strip

4.2 Steel plate specimen

An example of geometrically more complicated specimen is a steel plate. Monitoring of two-dimensional elements requires an application of sensor networks [13]. Optimal selection of network depends on specimen’s shape and might be crucial for SHM system efficiency. A scheme and dimensions of the investigated steel plate are shown on Fig. 6. In this case the rosette-shaped network of PZT transducers was permanently installed on the plate. Each transducer operated as actuator and sensor of elastic wave. The PAQ-16000D device was used as a generator and receiver of elastic waves.

In the single measurement cycle only one transducer was the actuator while the rest can sens the propagated wave signal. Therefore in each cycle 11 time signal histories were recorded. On the first stage of analysis, presented in this paper, only paths for alternate transducers were considered (Fig. 8a). The task of investigations was to detect and localize disturbance in form of additional mass. The measurements for 25 areas of disturbance with 5 localizations of mass in each area (9 localization in central area) were carried out (Fig. 8b). An example of the mentioned disturbance areas which were consequently numbered are shown in Fig. 9.

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Figure 7: The investigated steel plate specimen with a network of PZT transducers

Figure 8: The used rosette-shaped network of PZT transducers: a) analyzed measurement paths,

b) disturbance (mass) locations (dark circles)

Figure 9: Examples of defined 25 classes of disturbance (mass) localization

The assumption was that a presence of the additional mass in specified location takes effect on signals only for particular paths. The comparison of time signals for undamaged condition (without additional mass) with damage one (in form of additional mass) are shown on Fig. 10.

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Figure 10: Comparison of elastic wave signals for normal and abnormal condition in case of the

disturbance located on the wave path (P 3-9 ) and beyond the path (P 6-12)

It is easy to notice that the disturbances introduced by discontinuity are visible in case of these paths which transit through the area with the additional mass.

If compare undamaged and damaged state it is easy to notice that presence of disturbance on the wave path results in significant decrease of amplitudes related to a first recorded wave package (passing trough the disturbance). Moreover amplitudes of a second wave package (reflected from specimen boundary) also changes. Analyzing wave signals for damaged states it can be found that any additional packages reflected from discontinuity are noticeable. Therefore as a characteristic signal parameter the ratio of first and second package amplitudes was defined.

The objective of further analysis was identification of damage appearance and classification its localization to one of 25 classes considered. In damage detection and evaluation task feed-forward NNs were used. An input vector consisted of 12 parameters corresponding to paths P 1-7, P 2-8, … , P 12-6. Due to the large number of NN parameters to be evaluated a direct classification (algorithm 0) for undamaged class and 25 damaged classes was impossible. Thus the number of subclasses was defined (Fig. 11) and multilevel classification was perform. A classification algorithm I shows a diagram in Fig. 12. The discussed algorithm consists of 4 levels.

Figure 11: An example of defined subclasses in the task of disturbance localization (algorithm I)

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Figure 12: An algorithm of multilevel classification: a percentage classification efficiency and a

number of patterns classified erroneously

The obtained results of damage detection, it means the first level of classification for undamaged (unD) and damaged (D) cases was performed perfectly. Also further two-level classification for two damage classes D-I including both D-II and D-III classes (shown in Fig. 9) produced desired results. However, the next two-level classification (D-I vs D-II ) was performed with an insignificant error (3 patterns were classified erroneously). At the final step multilevel classification was performed. A separation to D-I-1, …, D-I-6 and D-II-1, …, D-II-6 classes was done with an error about 10%. Unfortunately a more precise classification based on the set of P 1-7, P 2-8, …, P 12-6 paths was impossible. Thus in the further studies additional paths should be considered.

5 Conclusions

Results obtained for the investigated specimens show that the presented idea of a diagnosis system can be used for the purpose of damage tests and structural health monitoring. Thanks to the application of NNs even complex signals can be used for anomaly detection and damage evaluation. In case of the investigated 2D specimen, which is geometrically more complicated a crucial role plays an algorithm of damage location. This is also due to the fact that a number of used PZT transducers in a rosette-shaped network causes the large amount of wave paths which should be analyzed in order to reach a better accuracy of the damage diagnosis system.

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Acknowledgments

The Polish Ministry of Science and Higher Education is gratefully acknowledged for its financial support to the presented research activity, Grant No. N N501 134336.

The presented research is also supported by Podkarpackie scholarship fund for Phd candidate.

References

[1] WASZCZYSZYN, Z., ZIEMIAŃSKI, L. Neural networks in the identification analysis of structural mechanics problems. In: Parameter identification of materials and structures, CISM Courses and Lectures, 469, p. 256-340, Springer-Wien, 2005.

[2] LEE, B.C., STASZEWSKI, W. Lamb wave propagation modelling for damage detection: II. Damage monitoring strategy. Smart Material Structures, vol. 16, 2007; p. 260-274.

[3] OSTACHOWICZ, W., KUDELA, P., MALINOWSKI, P., WANDOWSKI, T. Damage localization in plate-like structures based on PZT sensors. Mechanical Systems and Signal Processing, vol. 23, 2009, p. 1805-1829.

[4] GIURGIUTIU, V., CUC, A. Embedded Non-destructive Evaluation for Structural Health Monitoring, Damage Detection, and Failure Prevention. The Shock and Vibration Digest, vol. 37, 2005, p. 83-105.

[5] ZHAO, X., GAO, H., ZHANG, G., AYHAN, B., YAN, F., KWAN, C., ROSE, J.L. Active health monitoring of an aircraft wing with embedded piezoelectric sensor/actuator network: I. Defect detection, localization and growth monitoring. Smart Mater. Struct., vol. 16, 2007, p. 1208-1217.

[6] STASZEWSKI, W.J., LEE, B.C.; MALLET, L., SCARPA, F. Structural health monitoring using laser vibrometry: I. Lamb wave sensing. Smart Mater. Struct., vol. 13, 2004, p. 251-260.

[7] LEE, B.C., STASZEWSKI, W.J. Modelling of Lamb waves for damage detection in metallic structures: Part I. Wave propagation, Smart Mater. Struct., 12, p. 804-814, 2003.

[8] HERNANDEZ-GARCIA, M.R. AND SANCHEZ-SILVA, M. Learning machines for structural damage detection, In: Intelligent Computational Paradigms in Earthquake Engineering, Idea Group Publishing, p. 158-187, 2007.

[9] NAZARKO, P., JUREK, M., ZIEMIAŃSKI, L. Elastic waves in structure tests: I. Signal processing, Zeszyty Naukowe Politechniki Rzeszowskiej, 267, p. 37-42, 2009 (in Polish).

[10] MADZAROV, G.; GJORGJEVIKJ, D., CHORBEV, I. A Multi-class SVM Classifier Utilizing Binary Decision Tree, Informatica, 33, p. 233–241, 2009.

[11] NAZARKO, P. Comparative analysis of Auto-associative NNs and SVMs applied to patterns classification in the damage detection system. 19th International Conference on Computer Methods in Mechanics, 2011, p. 379-380.

[12] NAZARKO, P., ZIEMIAŃSKI, L. Towards application of Soft Computing in Structural Health Monitoring, In: Artifical Intelligence and Soft Computing, LNAI 6114, Springer-Verlag Berlin Heidelberg, p. 56–63, 2010.

[13] STASZEWSKI, W.J., WORDEN, K. Overview of optimal sensor location methods for damage detection. 8th SPIE Symposium on Smart Structures and Materials, Conference on Modeling, Signal Processing and Control of Smart Structures, 2001, vol. 4326, p. 179-187.

84


Technological progress in production, logging and processing of the biomass

Witold Niemiec, Feliks Stachowicz, Mariusz Szewczyk, Tomasz Trzepieciński

Rzeszów University of Technology Faculty of Civil and Environmental Engineering, Faculty of Mechanical Engineering and Aeronautics e-mail: [email protected], [email protected], [email protected], [email protected] Abstract

Abstract

Significant increase of the amount of plantations of energetic plants mainly with ligneous sprouts causes the necessity of searching new technologies allowing for efficient crop and further its in-coming processing. If for large-area plantations exist specialized technological means but in case of cultivation on small areas there is a lack of economically justified machines allowing logging and processing of plant biomass. The production of plant biomass for own needs by a small farm requires the application of agricultural machines adjusted for the scale of production. In the paper unique constructions of machines and devices being a composition of technol-ogy of energetic plant production were presented. Technical solutions of such machines and devices were worked out and patented in Rzeszow University of technology and they are to be wide tested together with the biomass producers and in cooperation with Lvov State Agricultural University within the framework.

Key words: biomass, energy plants, organic waste utilization, renewable energy sources

1 Introduction

Among all kinds of renewable energy sources in Poland, the great potential possible to fast utilization is in biomass especially in biomass of fundamental raw materials i.e. in straw, wood and energetic plants. Actual energetic policy of member state of European Union fa-vours plant production destinied to energetic aims by direct combustion of lignified parts of plants or by processing on the others energy carrier. Because of the almost universal, multi-purpose dependence on biomass, it is important to understand the interrelations between these many uses, and to determine the possibilities for more efficient production and wider uses in future. The success of biomass energy will most probably depend upon the use of reasonably advanced technology. Indeed, if bioenergy is to have a long-term future, it must be able to provide what people want: affordable, clean and efficient energy forms such as electricity, and liquid and gaseous fuels [1]. Large areas of former cropland and unexploited plantation, for-ests and woodlands are likely to be available in most countries to provide a significant bio-

85

Witold Niemiec, Feliks Stachowicz, Mariusz Szewczyk and Tomasz Trzepieciński

mass energy contribution. The process of producing energy from biomass is a chain of inter-linking stages (Fig. 1), which are mutually dependent.

Figure 1: Fuel supply chain for wood biomass [2]

Establishing of energetic plants should consider the problem of their harvesting and final uti-lization so that whole operation process be profitable. In Rzeszow University of Technology the establishing technology of energetic plant plantation, harvest methods and technology of sludge processing were elaborated. Proposed solutions are based on special machines pro-tected by patents. Characteristic feature of proposed solutions is their readjust to agricultural needs of quite small farms in Southern Poland. Proposed technical resources are also cost attractive. Energetic willow, by its different types according to the local climatic condition allow to obtain in a short time very good amounts of wood mass per hectare. With a high pro-ductivity energetic willow can ensure the basic raw material for different applications in order to obtain compacted wooden products like solid bio-fuel or direct combustion products to produce energy. Production productivity of energetic plants depends on applied agrotechnics so workmanship and sequence of protective treatments during cultivation plants in order to get plentiful crop with high quality. The basic knowledge about usability of soil to agricul-tural production are physico-chemical properties of the soils, their chemical constitution, ter-rain hipsography climatic conditions and hydrogeological structure. Characteristics of mu-nicipal solid waste and its utilization in agreement with decree [4] and acts [5,6,7] are condi-tions of application of this fertilizer to the cultivation of energetic plants.

2 Machines for production and logging of the biomass

Characteristic common feature of proposed by Rzeszow University of Technology construc-tional solutions of machines is their readjust to agricultural needs of quite small farms in Southern Poland. Simple construction of proposed machines and instruments cause that they are also cost attractive. One of the premise of taking operations connected with a construction of new machines for planting, logging and processing of the biomass of plants with ligneous shoots is high cost of high-productivity machines. So that their application in small farms are not profitable. Meaningful growth of amount of energetic plant plantation mainly plants with

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ligneous shoots causes the necessity of exploration of new technologies allowing for efficient harvesting and further their processing. Over the last years took place progress in submitting solutions of specialized machines for harvesting and processing of biomass jogging from lig-neous shoots e.g. movers, wood splitten machines, chaff cutter for wood but the problem still exists and requires further searching of correct solutions. Particularly machines assigned for small plantations and adapter for terrain hipsography are searched.

The optimal solution for small farms producing biomass is building machines caught in hook-type coupling of farm tractor, which is their prime mover. Hitherto existing key attainments in development of energetic plant production technology was described in Table 1.

Table 1: Statement of machines and instruments which are components of production tech-nology of energy plants.

Operation Place and realization method Law condition Sludge processing: -stabilization, -thickening, -treatment.

Sewage-treatment plant Technology of sewage treat-ment realized in sewage-treatment plant

Transport of sludge in arable land

Road: - highway, - private.

Highway code

Fertilizer dosage on established plantation

Preparation and fertilization of arable land:

- superficial, - injectional [8, 9]

Acts, decrees and good agricul-tural practice

Investigation of interaction on human and environment

Ecosystem components stud-ied in surround of estab-lished plantation:

- soil - water [10]

Acts, decrees and decisions

Production and storage of cuttings

Farm area [11] Industrial safety requirements and conditions of cutting stor-age

Planting, sowing Area of land [12]

Good agricultural practice and nutritional plant requirements

Cultivation and protection of plantation

Area of land: - manual work - mechanical work

Program of protection and cul-tivation in agreement with good agricultural practice

Harvest produced biomass On plantation: - manual, - mechanical [13, 14]

According to processing aim

Initial processing of the biomass

On plantation or nearest of them: - manual, - mechanical [13, 15]

According to processing aim

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Attention: Mentioned in table 1 reference marks contain complete information about pointed equipments

Till now the base prime mover for agricultural machines are farm tractors with diversified power. In case of establishing, protective treatments, logging and processing of the biomass in plantation of the energetic plants the farm tractors are basic prime mover of specialized ma-chines. Moreover most often farm tractors transport crop from plantation terrain to further processing or to final energetic biomass management.

Design process of a new machine started from building of conceptional spatial model of con-struction with Autodesk Inventor program. Autodesk Inventor allows to attribute kinematic constraints between particular movable parts of the machine and further is enable to observe possible collisions between consisted parts of the machine. The example conceptional model of the machine is presented in Fig. 2 in relation to the mover for the bushes with feeding arm and hydraulic driver of the moving gang. Autodesk Inventor allows to carry through kine-matic and dynamic analysis of mechanisms working. In order to determine relations between mate components may be used wide range of motion constraints and elastic or damping ele-ments as well as definition of friction coefficient in every constraint. To understand the es-sence of the kinematic effects program demonstrates simulation in a form of spatial visualiza-tion directly on model of analyzed mechanism. The stages of design process are preceded by synthesis and next by using analysis techniques verifies functionality of the mechanism and if necessary back to synthesis in order to make modification until it obtains satisfying construc-tion.

Figure 2: Mover model performed using Autodesk INVENTOR program

During the designing of mechanical elements appears a question if specified element with-stand load appears in normal operating. In complex constructions analytic determination of the most efforted places responsible for element destruction is more difficult and often impos-sible. In order to solve this problem carried out the optimization of numerical construction of the mover using ABAQUS program based on finite element method (FEM). ABAQUS allows analyzing physical models of real processes by putting special emphasis on geometrical non-

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linearities caused by large deformations, material non-linearities and complex friction condi-tions. The dimension of the geometrical model of the mover frame was corresponded to the conception model.

Requisite condition to begin the computation using FEM is preparation of accurate numerical model of selected construction and next simplification and digitizing of the model in ABAQUS in order to receive equivalent model to the mathematical model of continuous me-dium. Simplification of the model consists in removing unnecessary details such as small holes, roundings, chamfers which do not influence meaningfully on accuracy of solutions for the purpose of fast processing of the model. Digitizing consists in division of the continuous medium on finite numbers of elements of specified shape. In order to obtain required accu-racy of the searching solution used elements should be possible small so that approximated inside elements functions may be approximated using multinomial. Nevertheless the reduc-tion of elements number leads to increasing of number of searched function of node values which simultaneously causes lengthen time of computation. So most often heterogeneous di-vision of the model on elements was used. In places of expected high stress gradient mesh elements should be concentrated. The following stage of FEM model creation is taking into consideration boundary conditions and parameters describing material of the mover frame. The mover frame is constructed of S235JR constructional steel with following material pa-rameters [16]: density ρ = 7865 kg/m3,Young’s modulus E = 210 GPa, Poisson’s ratio v = 0.33, yield stress ReH = 300 MPa. The mover frame is composed with 38307 4-node ele-ments called C3D4 in Abaqus terminology. To the end of the cantilever jib on which is at-tached saw resultant forces resulted from the cutting process were imposed. Values of these forces were determined in this way so that to introduce construction into first plastic strain. Calculations were performed using the implicit finite element code. In the implicit method the internal forces are made to balance with the external force through an iterative procedure, from with the deformed state after a time increment can be obtained. One of the merits of this method is that the time increment can be relatively large because of conditional stability of the implicit time integrator and static solutions can be always obtained by natural characteris-tics of the method. For the Newton-Raphson’s iterations to solve, the time step is controlled by Abaqus automatic incrementation technique. The double precision executable is used in this analysis. The global equation in models based on FEM is represented as

{ } [ ]{ } [ ]⎭⎬⎫

⎩⎨⎧+= dMdK)t(F &&

(1)

where [K], [M] and [F] are the global stiffness, mass and force matrices, respectively. d are the nodal displacements and d&& are the nodal accelerations.

The analysis available from ABAQUS that is used in the model handles non-linearity’s from large displacements effects, material non-linearity and boundary non-linearity’s such as con-tact, sliding and friction. Solution is obtained as series of increments with iterations to obtain equilibrium within each increment. Implicit method enables full static solution of the defor-mation problem with convergence control. So, theoretically the time increments size can be large but practically however it is reduced by the contact conditions present between the sheet and die and the computer time increases almost four times with increase in elements.

The aim of the simulation was the determination of places in construction potential endanger into failure. In order to determine factual strain values in mover frame necessary is analytical

89


or experimental evaluation of real value of forces load of frame. The place of the most ef-forted is welded joint between mover frame and cantilever jib (Fig. 3). Analysed construction is relatively simple so it was possible with certain approximation the determination of places endangered to failure without application of advanced programs. However presented analysis progress will be used to analyse more complex machines e.g. willow and bush harvester [13].

Figure 3: Distribution of Huber-Mises-Hencky stress in frame of mover

Biomass may be processed directly on chips by using harvester [13] or by using wood cutter [15], especially for cutting on specified pieces bevelled energetic plants or branches constituting discard from e.g. cross-cutting of the fruit tree in orchard. In agreement with registered design wood cutter [15] characterizes by that cutting gang has replaceable heads with three, four or six cutters allowing for change of length of cutting elements.

Discarded biomass e.g. wood, municipal solid waste, discards of fruit-and-vegetable process-ing are main sources of hide and often gone lost energy. Economic meaning have also dis-cards come into beginning in logging of raw material for industrial processing e.g. wood log-ging in the forests and derivative timber i.e. branches and trimmings. Disadvantage of using biomass from food industry is large amount of moisture so before using green waste as a fuel for furnace, it should be dry or mixing with other king of organic materials. Essential meaning for environment protection, energetic utilization and production of plants have municipal solid waste which quantity in town planned regions grows fast. On Fig. 4 was presented an example of technology of their utilization.

Renewable energy sources (RES) may be essential part of energetic balance of individual re-gions of our country. RES may contribute to increase energy safety of the region particularly for improvement of energy supply in areas with weakly developed power of energetic infra-structure. Potential the greatest receiver of energy from renewable energy sources may be

90


agriculture, housing and communication. Especially in regions with high unemployment RES create new possibilities in range of new workplaces. But agriculture areas characterized by strong impurity which are not suitable for food growing may be used for plant cultivation to produce biofuel. Biufuels in general includes any solid, liquid or gaseous fuels produced from organic matter, either directly from plants or indirectly from industrial, commercial, domestic or agricultural wastes.

Figure 4: Technology outline of organic waste utilization

3 Summary

In the subject area of machines characterized by low productivity and destined for working in small plantations as well as verified in practice while field work there are not many commercial offers. Characteristic feature of Polish agriculture especially the area of southern country is size reduction and low degree of mechanization as well as limited buying power. In

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this situation lasts searching of construction solutions complying with conditions of small producers requirements in which farms is small power farm tractor usually with primary equipment. Considering the efficiency of application of proposed machines for production, logging and processing of the biomass in small farms a few factors should be taken into account. First of all should be considered largeness of farm and in consequence demand on manpower and grade of accessibility of high power farm tractors. From point of view of possibility of machine utilization should be considered terrain hypsography and soil structure. The advantage of proposed solutions is their uncomplicated construction which is connected with low production cost and simple machine operation. A low mass of working tools favours carrying out the agricultural operations on fenland.

References

[1] ROSILLO-CALLE, F., de GROOT, P., HEMSTOCK, S.L., WOODS, J. The biomass assess-ment Handbook, London, 2007, ISBN978-1844075263.

[2] STOCKINGER, H., OBERNBERGER, I. Systemanalyse der Nahwärmeversorgung mit Bio-masse, volume 2 in Thermische Biomassenutzung series, dbv-Verlag der Technischen Univer-sität Graz, Graz, 1998, ISBN978-3950198010.

[3] Energia odnawialna - szansą dla rozwoju gmin, Wojewódzki Fundusz Ochrony Środowiska i Gospodarki Wodnej w Katowicach, Katowice, 2010.

[4] Rozporządzenie Ministra Środowiska z dn. 1.08.2002, w sprawie komunalnych osadów ściekowych; Dz.U. Nr 134, poz. 1140.

[5] Ustawa z dn. 27.04.2001r o odpadach. Dz.U. Nr 62, poz. 62.

[6] Ustawa z dn. 27.04.2001 Prawo ochrony środowiska Dz.U. Nr 62.poz 627. z późniejszymi zmianami.

[7] Ustawa z dn. 18.07.2001 Prawo wodne Dz.U. Nr 115, poz.1229.

[8] NIEMIEC, W. Urządzenie do iniekcyjnego dawkowania do gleby sypkich nawozów organicznych i mineralnych, P 382062, 2007.

[9] NIEMIEC, W., PUCHAŁA, J. Urządzenie do wprowadzenia cieczy pod powierzchnię gleb i łąk, W 39050, 1983.

[10] NIEMIEC, W. Urządzenie do zbierania i pomiaru infiltrującej wody w warunkach polowych, W 116896, 2007.

[11] NIEMIEC W., et al. Urządzenie do produkcji zrzezów, P 384427, 2008.

[12] NIEMIEC, W., et al. Sadzarka zrzezów roślin o zdrewniałych pędach, during application.

[13] NIEMIEC, W., et al. Kombajn do zbioru i rozdrabniania zdrewniałych pędów roślin oraz gałęzi, W 119895, 2011.

[14] NIEMIEC, W., et al. Kosiarka do drzewiastych roślin, P 386842, 2008.

[15] NIEMIEC, W., et al. Sieczkarnia do drewna, W 116926, 2007.

[16] MALAG, L., KUKIEŁKA, L. Numerical Analysis of Strains and Stresses in Stretched Speci-mens at Microstructure Level. In Proc. Appl. Math. Mech., vol. 9, 2009, no 1, p. 347 – 348.

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Analysis of failures of the Krosno water network

Katarzyna Pietrucha, Andrzej Studziński

Technical University of Rzeszow Civil and Environmental Engineering Faculty, Department of Water Supply and Sewerage Systems


Abstract

In the article analysis of failures of the Krosno water network has been presented. In the work the analysis of the failure frequency for individual kinds of waterworks (main, distribution and water supply connections) on the example of the Krosno water network was also presented. An analysis based on exploitation data of the water network get from Municipal Services Office in Krosno in years 2005÷2009 was carried out. In the work the analysis of the failures depended on the diversity of applied materials, age and diameters for individual kinds of waterworks was also presented.

Key words: Krosno water network, the failure indicators and analysis

1 Introduction

The Krosno water supply network covers an area of 11 municipalities of Krosno and Sanok counties (Besko, Chorkówka, Iwonicz Zdroj, Jedlicze, Korczyn, Kroscienko Miejsce Piastowe, Rymanów, Wojaszówka, Zarszyn and the city of Krosno). The water network supplies water to about 100 000 recipients of the city of Krosno and neighbouring municipalities. The number of residential water supply connections in all served places is 5 730, including 4 675 terminals located in the Krosno municipality. The scheme of the Krosno network is shown in fig. 1.

The Krosno water pipeline is supplied with water from three water treatment plants (WTP), taking raw water from three independent surface water intakes, located on the river Wislok in Sienawa, Iskrzynia and on the river Jasiołka in Szczepańcowa.

Water is provided to consumers via a water pipe network having radial-ring arrangement, which is beneficial to the reliability of water supply system. Currently, the water supply network has a total length of about 604,7 kilometres and is made of the following materials: steel pipes (34%), cast iron pipes (26%), PVC pipes (22%), PE pipes (18%). The life of the water supply network is as follows: up to 5 years - 6%, from 6 years to 10 years - 12%, from 11 years to 20 years - 25%, from 21 to 30 years - 22%, from 31 to 50 years - 33%, more than 50 years - 3%.

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The purpose of this study is to characterize the unreliability of the Krosno water-pipe network. Detailed analysis of the water network failure, should be a main element of the managing system of the urban water networks, particularly in strategic modernization plans [2,9]. The calculations were made based on the operational data on the water-pipe network in the town of Krosno, developed based on the failure protocols received from the Municipal Enterprise for Communal Economy in Krosno.

Figure 1: The scheme of the Krosno water network

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2 Failures of the Krosno Water Network

The main criterion for assessing the state of water pipes is the failure rate index - λi. Failure rate index estimator per year for particular type of water pipes (mains, distributional and water supply connections), was determined from the formula [3,5,11]:

Δtlkλ

i

ii ⋅= (1)

where: λi – failure rate index estimator per year for particular type of water pipes per one

year, [km-1a-1]; ki – number of failures in one year for particular type of water pipes; li – the lenght of particular type of water pipes, on which failures appeared per one

year, [km]; i – type of water pipes (M - mains, R - distributional, P - water supply

connections); Δt – the lenght of time equal 1 year, [1 rok].

Table 1 shows the unit values of the failure rate in the Krosno water-pipe network in the years 2000÷2010.

Table 1: The length, number of failures and the failure rate for particular type of water pipes in the years 2000÷2010

Year 2005 2006 2007 2008 2009 2010 Mains

The length of water pipes 86,8 86,8 86,8 86,8 86,8 86,8

Number of failures 84 101 75 59 46 42 λM 0,97 1,16 0,86 0,68 0,53 0,48

Distributional The length of water

pipes 241,1 242,2 244,6 244,9 245,9 247,8

Number of failures 51 49 40 50 46 44 λR 0,21 0,20 0,16 0,20 0,19 0,18

Water supply connections The length of water

pipes 247,1 249,9 253,1 259,0 264,2 270,1

Number of failures 151 204 119 147 114 141 λP 0,61 0,82 0,47 0,57 0,43 0,52

The lowest failure rate have distribution pipelines (λRśr = 0.19 km-1a-1) and the highest failure rate have main pipelines (λMśr = 0,78 km-1a-1).

The European criteria say that the pipeline needs repairing when the failure rate index exceeds 0.5 km-1a-1 [7, 10, 13, 14, 15].

However, one should seek to the following values of the failure rate index:

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mains: λ ≤ 0,3 km-1a-1, distributional: λ ≤ 0,5 km-1a-1, water supply connections: λ ≤ 1,0 km-1a-1.

The calculations show that the distribution pipelines and the water supply connections in Krosno are in good condition, but one should focus on improving the technical state of the main water pipelines.

Figure 2 shows the percent of failures in the main water pipes, the distribution pipes and the water supply connections depending on the material from which they were made. 63% of the failures occurring in the main water pipes happened in the cast iron pipes, which results from a significant share of this material in the construction of these pipelines and their significant age. The distribution pipelines are characterized by high failure rate of iron pipes (51% of all failures), and PVC pipes (35%).

Most failures in the water supply connections, as many as 66%, occur in steel pipes, this is due to their poor technical condition.

The lower number of failures in pipelines made of PVC and PE is caused by the fact that they are part of the younger sections of water network and that they are resistant to corrosion.

steelżeliwo

PCVPE

mains

distributional

water supply conections

16,12%

63,00%

20,88%

0

13,00%

51,12%

34,98%

0,90%

65,62%

0

32,95%

0,29%

0,00%

10,00%

20,00%

30,00%

40,00%

50,00%

60,00%

70,00%

[%]

Figure 2: The failures in the main water pipes, the distribution pipes and the water supply connections depending on the material from which they were made in 2005÷2010

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The detailed analysis of the failure rate in water pipes in the years 2005÷2010 showed that:

Pipes made of PE are characterized by the lowest failure rate. In the water supply connections the failure rate index does not exceed 0,11 km-1a-1 and in the distribution pipelines 0,04 km-1a-1.

Iron pipelines in the main pipelines show the highest failure rate. The average failure rate is 1,52 km-1a-1. In the distribution pipelines the average failure rate is 0,36 km-1a-1.

The highest failure rate in PVC pipes is seen in the water connections, from 0,7 to 1,27 km-

1a-1, and the lowest in the distribution pipelines, from 0,23 to maximum of 0,41 km-1a-1. In the main water pipes the average failure rate was 0,73 km-1a-1.

In the steel pipelines the highest failure rate is in the water supply connection, it ranges from 0,76 to over 1,37 km-1a-1, the main pipelines have the average failure rate up to 0,3 km-1a-1. The distribution pipelines have the lowest failure rate, which amounted to 0,09 km-

1a-1.

Comparing the determined average failure rate in the water supply system made of different materials with the required values, it is concluded that (figure 3):

In the case of the main pipelines made of cast iron and PVC the average failure rate is, respectively, 1,52 and 0,73 km-1a-1, while the required value of failure rate index in the main water network is λMwym = 0,3 km-1a-1, the steel pipes, however, have the average failure rate 0.30 km-1a-1.

In the case of the distribution pipelines, the average failure rate for pipelines made of steel (0,07 km-1a-1), made of iron (0,36 km-1a-1), made of PE (0,01 km-1a-1) and PVC (0,35 km-

1a-1) is lower than the required value λRwym = 0,5 km-1a-1.

In case of the water supply connections, the average failure rate in steel pipelines and PVC pipelines (values respectively 1,07 and 1,01 km-1a-1-) is higher than the required value λPwym = 1,0 km-1a-1.

Table 2 shows the percentage of failures depending on the diameter and material of water pipes in the years 2005÷2010. It is clearly visible that the most often the failures occur in the water connections with a diameter of 32 mm, made of steel (14,5% of all failures). The next frequent are the failures in pipes made of PVC and steel, with a diameter of 40 mm, respectively 12% and 9,6% of all failures.

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steeliron

PEPVC

mains

water supply conections

distributional

0,30

1,52

0,00

0,73

1,07

0 0,04

1,01

0,070,36

0,010,350,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

The average failure rate

index [km-1a-1]

Figure 3: The average failure rate index for particular type of water pipes in the years

2005÷2010

Table 2: The percentage of failures depending on the diameter and material of water pipes in the years 2005÷2010

Diameter Steel Iron PVC PE 25 2,7% - 0,24% 0,00% 32 14,5% - 0,47% 0,08% 40 9,6% - 12,00% 0,39% 50 8,8% - 4,18% 0,00% 63 0,6% - 1,34% 0,32% 80 1,8% 4,74% 3,00% 0,16% 100 0,5% 4,26% 3,16% - 150 2,0% 3,47% 4,03% - 200 0,2% 0,39% 0,47% - 250 0,2% 4,42% 0,00% - 300 0,0% 2,68% 0,00% - 350 0,0% 2,05% 0,00% - 400 0,0% 3,63% 0,00% - 500 1,1% 2,53% 0,00% -

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3 Conclusion

Based on the analysis of the results of the studies, the following conclusions and statements were made:

the average failure rate for the main pipelines is λMśr = 0,74 km-1a-1, the distribution pipelines λRśr = 0,19 km-1a-1 and the water connections - λPśr = 0,56 km-1a-1,

the majority of failures (55,22%) happen in the water connections (25 to 63 mm diameter), representing about 44% of the total length of the pipelines,

the lowest failure rate is in the distribution pipelines made of PE - λPEśr = 0,01 km-1a-1, which results from their use since the 1990s,

for the water connections made of steel the average failure rate is λstalśr = 1,07 km-1a-1, the highest average failure rate is found in the cast iron main water pipelines λżeliwośr = 1,52 km-1a-1, which is caused by the fact that steel and iron are the oldest materials used to build that water supply network,

the value of failure rate indexes corresponds to national trends [1,4,6,8,12], the declining trend in both the number of failures and failure rate in water pipelines is seen.

Acknowledgements

Scientific work was financed from the measures of National Center of Research and Development as a development research project No N R14 0006 10: “Development of comprehensive methodology for the assessment of the reliability and safety of water supply to consumers” in the years 2010-2013.

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[12] HOTLOŚ, H. Ilościowa ocena wpływu wybranych czynników na parametry i koszty eksploatacji sieci wodociągowych. Prace naukowe Instytutu Inżynierii Ochrony Środowiska Politechniki Wrocławskiej, nr 84, monografie nr 49. Wrocław, 2007.

[13] KWIETNIEWSKI M., RAK J. Niezawodność infrastruktury wodociągowej i kanalizacyjnej w Polsce - stan badań i możliwości jej poprawy. Komitet Inżynierii Lądowej i Wodnej PAN Warszawa, 2009.

[14] KWIETNIEWSKI, M., ROMAN, M., KŁOS-TRĘBACZKIEWICZ, H. Niezawodność wodociągów i kanalizacji. Arkady, Warszawa, 1993.

[15] RAK, J. Podstawy bezpieczeństwa systemów zaopatrzenia w wodę. Monografie Komitetu Inżynierii Środowiska Polskiej Akademii Nauk, vol. 28, Lublin, 2005.

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Authors’ guidelines for paper submission

First Author, Second Author, Third Author



Abstract

The abstract is to indicate the subject of the paper, how the author proposes to develop the subject and its overall objective, aim or outcome. Abstract is to be in English in 10pt Times New Roman font. It should be concise and short approximately 150 words.

Key words: paper instructions, format, paper size, length

1 Introduction

The formatting of this document indicates the editor requirements for the submission of the articles for Selected Scientific Papers with some enhancements for this particular using. To make it easier for authors this document may be used as an example.

Only papers formatted according to the guidelines indicated in this document can be accepted for publication.

2 Requirements for submission of papers

Papers are to be in English on A4 paper in 12pt Times New Roman font. The page setup is top and bottom 3,5 cm, left and right 2,5 cm. The length of the paper should not exceed of 8 up to 12 pages (in reason cases can be exceed). Documents should not be page-numbered. The deadline for submission of full paper is all year.

2.1 Method and medium of submission

Papers will be reviewed by two independent reviewers in terms of clarity of subject, the objective and aim or intended outcome, adequacy of research development, potential contribution to knowledge, rigor and bibliographic style, language and writing style.

101

Adriana Xxx, Zuzana Yyy and Nataša Zzz

2.2 Length of paper

The final paper should be: of 8 up to 12 (8,10,or 12 pages, including first page and references), in the prescribed font and letter sizes and using the correct typing area per page as in this example.

3 Formatting requirements

3.1 Title Page

The title page must give the title of the paper, all authors with their affiliations and up to five keywords. The title page shall appear as the first page of this document. The body of the text must start after the key words.

3.1.1 Equations

Equations should also be numbered consecutively in parentheses on the right hand side of page for reference purposes in the text.

E = mc2 (1)

3.1.2 Tables and Figures

Tables, Figures and Pictures should be centered, numbered consecutively and referred to in the text as Table 1 and Fig. 1. The Pictures, Figures and Tables shouldn’t be coloured.

Figure 1: Description of figure

Allow at least 1 line space below figure descriptions and text and 1line spaces above table descriptions and text.

Table 1: Description of Table

Xxx Yyy 1 120 7 100

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3.2 Citations

References cited in the text should be indicated by consecutive numbers in parentheses [1,2,3] on the same line as the text and the full source information listed under the heading ‘References’ at end of paper. Examples given below: for articles in journals [1 & 2], conference proceedings [3] for books [4] and a website reference [5].

4 Conclusion

The method of submission is as an attachment by e-mail in MS Word using Windows 97 or later version as well as the written original sent to e-mail [email protected] in accordance with the sample instructions.

Acknowledgements

If appropriate ...

References

[1] STN 73 0036: 1997, Seizmické zaťaženie stavebných konštrukcií, ÚNMS SR, Bratislava, 1997.

[2] HANNA, A.M., NGUYEN, T.Q. Shaft resistance of Single Vertical and Batter Piles in Sand Subjected to Axial Compression Loading. In ASCE, Journal of Geotechnical and Environmental Engineering, vol. 129, 2003, no 3, p.15-28.

[3] SKLENÁRIKOVÁ, Z. One hundred years since death of Karl Pelz. In G - Slovak Journal for Geometry and Graphics, Bratislava: SSGG, vol. 5, 2008, no 9, p. 31 - 44 (in Slovak).

[4] SILVA, J.M., ABRANTES, V. Consequences on brickwork of clay brick and mortar differential movement. In Proceedings of XXV IAHS World Housing Congress, Lisboa, Junho-Julho, 1998, p.141-147, ISBN80-222-0102-2.

[5] ADDLESSON, L., RICE, C. Performance of Materials in Buildings. Oxford: Butterworth-Heinemann Ltd, 1995.

[6] OKRAGLIK, H. Sustainable housing: a case study of Australia’s first green home. http://www.rmit.edu.au/pr:ograms/sustainable(18/03/2005)

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The Slovak Republic Ministry of Culture has approved of the Selected Scientific Papers – Journal of Civil Engineering Reg. No.: EV 3398/09

ISSN 1336-9024

© Technical University of Košice, Civil Engineering Faculty, Slovak Republic

ISSN 1336-9024