PROJECT REPORT- PHASE I

On

ANALYSIS & DESIGN ASPECTS OF PRE-STRESSED MEMBERS USING F.R.P. TENDONS

Submitted in partial fulfilment for the award of the degree

Of

BACHELOR OF TECHNOLOGY In

CIVIL ENGINEERING By

GIRISH KUMAR SINGH 1011020021

Under the guidance of

Mr. SELVA CHANDRAN PANDIAN & Ms. ARUNA MALINI ASSISTANT PROFESSOR

DEPARTMENT OF CIVIL ENGINEERING

FACULTY OF ENGINEERING AND TECHNOLOGY

SRM UNIVERSITY

(Under section 3 of UGC Act, 1956)

RAMAPURAM-600089

LIST OF CONTENTS

i

ii

iii

iii

Iv

CHAPTHER NO. TITLE PA GE NO.

ACKNOWLEDGEMENT

ABSTRACT

LIST OF TABLE

LIST OF FIGURES

LIST OF SYMBOLS

1. INTRODUCTION 1

1. 1 Pre-Stressing 2

1. 2 Pre-Stress Concrete 5

1. 3 Pre-Stressed Beam. 6

1. 4 Pre-Stressing Steel 7

1. 5 Anchorage 9

1. 6 Losses in Pre-stressing 17

2. F

P

IBRE REINFORCED POLYMER FOR

RESTRESSING

19

2. 1 Literature Survey 20

2. 2 Historical Development And Use of FRP

Reinforcement

21

2. 3 Design Guidelines And Technical Committees 23

2. 4 Research Efforts 23

3. D ESIGN CRITERIA 26

3.1 Design of Pre-Stress Beam

3.1.1 Using Steel 27

3.1.2 Using FRP 30

3.2 Calculation of Losses

3.2.1 For Steel 33

3.2.2 For FRP 37

3.3 Anchorage Design 40

4. ANALYSIS RESULTS FROM ANSYS 41

CONCLUSION OF THE PROJECT 44

REFERENCES 46

ACKNOWLEDGEMENT

The undersigned wishes to express his sincere gratitude to Er. BabuRajendran A.G.M of

Chennai metro underground section phase II for providing the opportunity to work under Er.

SelvaChandranPandian of Mott Macdonald, Chennai. He is equally thankful to Er.

SelvaChandranPandian of Mott Macdonald, Chennai for giving his precious time and

providing guidance in the preparation of this project report. Despite his busy schedule, he has

been ever ready to find time for the problem and doubts for this report.

He is also very thankful to Ms.ArunaMalini for providing guidance for the completion of this

project report.

ABSTRACT

The purpose of this investigation is mainly a brief explanation about the advantages of FRP

over steel. The various uses and advantages of FRP are explained in this project. In this

project, we have taken a section of 3m length, 200mm width and 300mm depth and using a

parabolic tendon of eccentricity 100mm at the centre. We have design the section for FRP as

well as steel with the above data. The final stresses obtained is being verified with the help of

Ansys software. We have shown the result of steel straight tendon only in this mini project.

LIST OF TABLE

SR. NO. TITLE OF TABLE PAGE NO.

1 Fibre Properties 21

2 Distributed axial force 32

3 Comparison on the basis of losses 44

4 Conclusion on the basis of ACI440-04r 45

LIST OF FIGURES

SR. NO NAME OF FIGURE PAGE NO.

1 Prestress Concrete Diagram 2

2 Tendons 8

3 Types of prestressing steel 8

4 Anchorage 9

5 Prestressing Effect 9

6 Clamp Anchorage 10

7 Sleeve Anchorage 11

8 Contoured Anchorage 12

9 Metal Anchorage 13

10 Types of anchorage systems 14

11a Stress Distribution 16

11b Stress Distribution 16

12 Anchorage Plate 47

13 Model Prepared in Ansys 41

14 Deformation due to prestressing force 41

15 Stress Distribution in beam 42

16 Moment in the beam 42

17 Anchorage portion of the beam 43

CHAPTER 1

INTRODUCTION

1.1 PRE-STRESSING.

1.2 PRE-STRESS CONCRETE.

1.3 PRE-STRESSED BEAM.

1.4 PRE-STRESSING STEEL.

1.5 ANCHORAGE.

1.6 LOSSES IN PRE-STRESSING.

1.1 PRE-STRESSING The stress introduced in concrete or steel prior to the application of loads. At a given time

after transfer, the pre-stress is defined as the stress remaining in the material if all applied

loads, including the weight of the member, were temporarily removed. In other words, pre-

stress is the difference obtained by subtracting the stresses caused by the dead and live loads

from the prevailing stress at the time By this definition, the pre-stress is not changed

instantaneously by the application of any load, and remains a fixed quantity dependent upon

the designand loading history of the members.

This classification is based on the method by which the pre-stressing force is generated.

There are four sources of pre-stressing force: Mechanical, hydraulic, electrical and chemical.

Figure 1 - Prestress Concrete Diagram

EXTERNAL OR INTERNAL PRE-STRESSING

This classification is based on the location of the pre-stressing tendon with respect to the

concrete section.

PRE-TENSIONING OR POST-TENSIONING

This is the most important classification and is based on the sequence of casting the concrete

and applying tension to the tendons.

LINEAR OR CIRCULAR PRE-STRESSING

This classification is based on the shape of the member pre-stressed.

FULL, LIMITED OR PARTIAL PRE-STRESSING

Based on the amount of pre-stressing force, three types of pre-stressing are defined.

UNIAXIAL, BIAXIAL OR MULTI-AXIAL PRE-STRESSING

As the names suggest, the classification is based on the directions of pre-stressing a member.

The individual types of pre-stressing are explained next.

SOURCE OF PRE-STRESSING FORCE HYDRAULIC PRE-STRESSING

This is the simplest type of pre-stressing, producing large pre-stressing forces. The hydraulic

jack used for the tensioning of tendons, comprises of calibrated pressure gauges which

directly indicate the magnitude of force developed during the tensioning.

MECHANICAL PRE-STRESSING

In this type of pre-stressing, the devices includes weights with or without lever transmission,

geared transmission in conjunction with pulley blocks, screw jacks with or without gear

drives and wire-winding machines. This type of pre-stressing is adopted for mass scale

production.

ELECTRICAL PRE-STRESSING

In this type of pre-stressing, the steel wires are electrically heated and anchored before

placing concrete in the moulds. This type of pre-stressing is also known as thermo-electric

pre-stressing.

EXTERNAL OR INTERNAL PRESTRESSING EXTERNAL PRESTRESSING

When the prestressing is achieved by elements located outside the concrete, it is called

external prestressing. The tendons can lie outside the member (for example in I-girders or

walls) or inside the hollow space of a box girder. This technique is adopted in bridges and

strengthening of buildings.

INTERNAL PRESTRESSING

When the prestressing is achieved by elements located inside the concrete member

(commonly, by embedded tendons), it is called internal prestressing. Most of the applications

of prestressing are internal prestressing.

PRE-TENSIONING OR POST-TENSIONING PRE-TENSIONING

The tension is applied to the tendons before casting of the concrete. The pre-compression is

transmitted from steel to concrete through bond over the transmission length near the ends.

POST-TENSIONING

The tension is applied to the tendons (located in a duct) after hardening of the concrete. The

pre-compression is transmitted from steel to concrete by the anchorage device (at the end

blocks).

LINEAR OR CIRCULAR PRESTRESSING LINEAR PRESTRESSING

When the prestressed members are straight or flat, in the direction of prestressing, the

prestressing is called linear prestressing. For example, prestressing of beams, piles, poles and

slabs. The profile of the prestressing tendon may be curved.

CIRCULAR PRESTRESSING

When the prestressed members are curved, in the direction of prestressing, the prestressing is

called circular prestressing. For example, circumferential prestressing of tanks, silos, pipes

and similar structures.

FULL, LIMITED OR PARTIAL PRESTRESSING FULL PRESTRESSING

When the level of prestressing is such that no tensile stress is allowed in concrete under

service loads, it is called Full Prestressing (Type 1, as per IS:1343 - 1980).

LIMITED PRESTRESSING

When the level of prestressing is such that the tensile stress under service loads is within the

cracking stress of concrete, it is called Limited Prestressing (Type 2).

PARTIAL PRESTRESSING

When the level of prestressing is such that under tensile stresses due to service loads, the

crack width is within the allowable limit, it is called Partial Prestressing (Type 3).

UNIAXIAL, BIAXIAL OR MULTIAXIAL PRESTRESSING UNIAXIAL PRESTRESSING

When the prestressing tendons are parallel to one axis, it is called Uniaxial Prestressing. For

example, longitudinal prestressing of beams.

BIAXIAL PRESTRESSING

When there are prestressing tendons parallel to two axes, it is called Biaxial Prestressing.

MULTIAXIAL PRESTRESSING

When the prestressing tendons are parallel to more than two axes, it is called Multiaxial

Prestressing. For example, prestressing of domes.

1.2PRE-STRESS CONCRETE Concrete is strong in compression, but weak in tension its tensile strength varies from 8 to

14% of its compressive strength. Due to such a low tensile capacity flexural cracks develop at

early stages of loading. In order to reduce or prevent such cracks from developing, a

concentric or eccentric force is imposed in the longitudinal direction of the structural element.

This force prevents the cracks from developing by eliminating or considerably reducing the

tensile stresses at the critical mid span and support sections at service load thereby raising the

bending, shear, and torsional capacities of the sections.

The sections are then able to behave elastically and almost the full capacity of the concrete in

compression can be efficiently utilized across the entire depth of the concrete sections when

all loads act on the structure. Such an imposed longitudinal force is termed a prestressing

force that is a compressive force that prestresses the sections along the span of the structural

element prior to the application of the transverse gravity dead and live loads or transient

horizontal live loads.

The type of prestressing force involved together with its magnitude are determined mainly on

the basis of the type of system to be constructed and the span length. As a result, permanent

stresses in the prestressed structural member are createdbefore the full dead and live loads are

applied in order to eliminate or considerably reduce the net tensile stresses caused by these

loads.

With reinforced concrete, it is assumed that the tensile strength of the concrete is negligible

and disregarded. This is because the tensile forces resulting from the bending moments are

resisted by the bond created in the reinforcement process. Cracking and deflection are

therefore essentially irrecoverablein reinforced concrete once the member has reached its

limit state at service load. In prestressed concrete elements cracking can be controlled or

totally eliminated at the service load level.

The reinforcement required to produce the prestressing force in the prestressed member

actively preloads the member, permitting a relatively high controlled recovery of cracking

and deflection.

1.3PRE-STRESS BEAM Design of pre stressed concrete beams is based upon two distinct concepts which lead to two

design methods known as service load de-sign or working stress design, and ultimate design.

In service load design the stresses in the beam are calculated on the basis of the assumption

that concrete is an elastic material. These calculated stresses are to be less than or equal to

certain limiting stresses known as allowable stresses.

The allowable stresses are chosen so that the structure will perform its intended service

satisfactorily under service conditions while providing indirectly for the safety of the beam.

In ultimate design the flexural strength or ultimate moment of the section is calculated based

on the knowledge of behaviour of the beam. The calculated ultimate moment is to be equal to

or greater than the sum of moments of allforces each multiplied by a factor.

These areknown as load factors and are chosen so thatthe structure will be sufficiently safe

underthe service conditions. Moreover, ultimatedesign also requires certain ductility in

thebeam, so that prior to failure the beam willdeform sufficiently. Ductility is measuredby the

deformation of the beam at failure.In our present practice pre stressed concrete beams are in

most cases designed andproportioned by working stress design.

Theprovisions of ultimate design are used to checkthe flexural strength of a section that

hasalready been designed. Further more the provisions for ultimate design in our

presentspecifications are more suitable for calculating the flexural strength of a given

section.It should be pointed out that there is are relationship between working stress design

andultimate design. Although they have differentbases, in fulfilling the objective of one,

theobjective of the other is satisfied to a certain extent.It can be shown that the provisions

ofultimate design can be used to proportion asection with a more rigorous control of ductility.

The provisions of working stress design can then be used to check working stressesin the

section so designed.

Further more rational design of a section is considerablysimpler by ultimate design than by

service Load design.The purpose of this study is to develop amethod by which a prestressed

concrete beam canbe proportioned by the provisions of ultimatedesign. It is intended to show

the importanceof ductility in its influence upon the dimensions of the beam. In addition it is

intended to study the influence of compression steelon ductility and the proportions of a

section.

We will consider a simply supported bonded beam and assume that the strength of thebeam is

measured by flexure. We will assume that the only loads acting in addition tothe prestressing

force, are the weight of the beam the superimposed dead load and live load.

1.4 PRESTRESSING STEEL The development of prestressed concrete was influenced by the invention of high strength

steel. It is an alloy of iron, carbon, manganese and optional materials. The following material

describes the types and properties of prestressing steel.

In addition to prestressing steel conventional non-prestressed reinforcement is used for

flexural capacity (optional) shear capacity, temperature and shrinkage requirements. The

properties of steel for non-prestressed reinforcement are not covered in this section. It is

expected that the student of this course is familiar with the conventional reinforcement.

WIRES A prestressing wire is a single unit made of steel. The nominal diameters of the wires are 2.5,

3.0, 4.0, 5.0, 7.0 and 8.0 mm. The different types of wires are as follows.

1) Plain wire: No indentations on the surface.

2) Indented wire: There are circular or elliptical indentations on the surface. STRANDS A few wires are spun together in a helical form to form a prestressing strand. The different

types of strands are as follows.

1) Two-wire strand: Two wires are spun together to form the strand.

2) Three-wire strand: Three wires are spun together to form the strand.

3) Seven-wire strand: In this type of strand, six wires are spun around a central wire. The

central wire is larger than the other wires.

TENDONS A group of strands or wires are placed together to form a prestressing tendon. The tendons

are used in post-tensioned members. The following figure shows the cross section of a typical

tendon. The strands are placed in a duct which may be filled with grout after the post-

tensioning operation is completed.

CABLES

Figure 2 - Tendon

A group of tendons form a prestressing cable. The cables are used in bridges.

BARS A tendon can be made up of a single steel bar. The diameter of a bar is much larger than that

of a wire. Bars are available in the following sizes: 10, 12, 16, 20, 22, 25, 28 and 32 mm.

Fig 3:- TYPES OF PRESTRESSING STEEL

1.5ANCHORAGE

Anchorage are those mechanical plates which holds the prestressing force developed in the prestressing steel. It is used under both pre-tensioning as well as post-tensioning.

FIG4 :- ANCHORAGE

FIG5 :- PRESTRESSING EFFECT

TYPES OF ANCHORAGES :- (REFER ACI440-04R)

2.4.1 CLAMP ANCHORAGE—A clamp anchorage consists of grooved steel plates

sandwiching the FRP rod and held together by bolts. The force is transferred from the tendon

to the anchorage by a shear friction mechanism and is influenced by parameters such as the

roughness of the interface surfaces and the clamping force applied by the bolts. The

performance of the anchorage is improved by using a sleeve material (protection media) to

encase the tendon. This intermediary material with low stiffness and high ultimate elongation

smooth’s the lateral pressure distribution on the tendon (Malvar and Bish 1995). The length

of the anchorage may be varied, depending on the material chosen to ensure that the ultimate

strength of the tendon is reached.

FIG6 :- CLAMP ANCHORAGE 2.4.2 PLUG AND CONE ANCHORAGE—The plug and cone (or barrel and spike)

anchorage is made of a socket housing and a conical spike (Burgoyne 1988). Such a system is

particularly well suited to anchor Parafil tendons where the aramid fibers are not encased in

resin media but are held only by an outer protective sheath. Parafil is unique in its ability to

evenly distribute the aramid fibers around the spike, thereby achieving high anchorage

efficiency.

The gripping mechanism of the anchorage is similar to that of a wedge anchorage where the

tendon is held by the compressive force applied to the fiber by inserting the spike into the

barrel. This compressive stress together with the friction between the rod material and the

socket in addition to the spike generate a frictional stress that resists the slipping of the

tendon out of the socket. The field application of this system requires the removal of the

plastic sheath combing and spreading of the individual fibers and proper placement of the

spike with a uniform distribution of fibers all around it.

FIG7:- SLEEVE ANCHORAGE 2.4.3 STRAIGHT SLEEVE ANCHORAGE—In this anchorage the FRP tendon is

embedded in resin that fills a tubular metallic housing such as steel or copper. The potting

material ranges from non-shrink cement, with or without sand to expansive cement to epoxy-

based materials. In the case of non-shrink cement and polymeric potting materials the load-

transfer mechanism depends completely on bonding and interlocking between the anchorage

components. The mechanism of load transfer is by bond at the interface between the rod and

the filling material and between the filling material and the metallic sleeve. To increase the

bond between the anchorage components in such casesan internally threaded sleeve is used or

a rigid filler material such as sand is added to the resin or both. Filler in the resin also serves

to reduce chemical shrinkage of the resin during curing. To enhance the bond between the

tendon and the grout material, surface modifications such as braiding twisting or ribscan be

applied to the tendon. Harada and co-workers were among the earliest users of expansive

cementitious materials to fill straight metallic sleeve anchorages (Harada et al. 1993).

Expansive cement generates significant lateral pressure and increases the slipping resistance

of the tendon. The 25 to 40 MPa (3600 to 5800 psi) internal radial pressures developed by the

expansive cementitious materials are adequate for gripping FRP tendons with a wide range of

surface configurations without causing undue stress concentrations at the point of egress of

the tendon during quasistatic and cyclic loadings (Harada etal. 1997). Anchorages as long as

300 to 400 mm (12 to 16 in.) have been shown to be sufficient for developing the full

strength of CFRP tendons without slippage at the free end of the anchorage. The

effectiveness of such anchorages has also been demonstrated in elevated temperature

extended duration relaxation tests (Dye, Bakis, and Nanni 1998). At this time, the main

shortcoming of this type of anchorage appears to be the 2- to 3-day curing time for expansive

cementitious materials.

FIG8:- CONTOURED ANCHORAGE 2.4.4 CONTOURED SLEEVE ANCHORAGE- The contoured sleeve anchorage has the

same components as the straight sleeve anchorage. The principal difference between the two

systems is the varied profile of the inner surface of the contoured sleeve, which may be

linearly tapered or parabolically tapered.

The load transfer mechanism from the tendon to the sleeve is by interface shear stress, which

is a function of bonding, and radial stress produced by the variation of the potting material

profile. A conical profile with a constant taper angle is the most popular type of resin potted

anchorage. Kim and Meier (1991) developed a variable stiffness anchorage for CFRP

tendons. The work was based on concepts of a commercial anchorage developed by the Swiss

company BBR. The anchorage was made of a cone filled with an epoxy matrix containing

high-modulus ceramic filler. Holte Dolan, and Schmidt (1993) described a parabolic

anchorage with epoxy sand filler.The following parameters affect the performance of a

resinpotted anchorage length of the anchorage angle of theanchorage cone front radius of

anchorage cone modulus ofelasticity of the potted material, and length and

moduluscharacteristic of the “soft zone” in resin filler at the front ofthe anchorage. Potted

anchorages often fail through pullout of the tendon from the resin grout rather than by rupture

ofthe tendon. Practical drawbacks with this anchor includepre-cutting the tendons to length

and the curing time for thepotting material.

FIG9 :- METAL ANCHORAGE 2.4.5 METAL OVERLAYING- The die-cast wedge system forCFCC requires that the

tendon length be predefined so that ametal tube can be cast onto the tendon at a specific

locationduring fabrication with the result that adjustment on site islimited. The metal overlay

is added to the ends of the tendonby means of die-molding during the manufacturing process.

The die-cast molding can then be gripped at the location ofthe metal material using a typical

wedge anchorage. The useof this system is limited because of the inflexibility in thespecified

length of the tendon. The load transfer in thisanchorage is achieved by shear (friction) stress

which is afunction of the radial compressive stress and the friction atcontact surfaces.

2.4.6 SPLIT-WEDGE ANCHORAGE- Split-wedge anchoragesare generally preferred

because of their compactness ease of assembly reusability and reliability. This type of

anchorage can be subdivided into two categories systems with directcontact between plastic

or steel wedges and the tendon andsystems using a sleeve between the wedges and the

tendon.Wedge anchorages are widely used in anchoring steeltendons but should be modified

for use with FRP tendons byincreasing their length to reduce transverse stress on thetendon

and controlling roughness in the wedge to preventnotching the tendon. The number of the

wedges in the split-wedgeanchorage varies from two to six wedges inserted intothe barrel.

The main reason for increasing the number ofwedges is to provide a smoother lateral stress

distribution inthe radial direction of the tendon. The mechanism of grippingrelies on friction

and clamping force between the wedges barrel and tendon. Using a small taper on the wedges

is ofgreat importance to provide a smooth and uniformly distributedtransverse stress.

A metallic anchorage was developed as part of the ISISCanada program (Sayed-Ahmed and

Shrive 1998; Campbellet al. 2000) for 8 mm LeadlineCFRP tendons. Theanchorage consists

of three components: a stainless steelbarrel with a conical socket a four-piece stainless

steelconical wedge set and a thin soft metal sleeve that is placedbetween the wedges and the

tendon. The distinct feature ofthe anchorage is that the taper angle of the wedge is 0.1degrees

greater than that of the inner surface of the barrel.The difference in angle between the barrel

and the wedgeshelps to produce more desirable radial stress distribution onthe tendon and

ensures that failure of the tendon occursoutside the anchorage. An experimental and

analyticalinvestigation of this anchorage has been reported by Al-Mayah,Soudki, and

Plumtree (2001). Non-metallic versions of this anchorage in which the elements are made

either from ultra-high-performance concrete (UHPC), where the barrel is wrapped with CFRP

sheet or from carbon fiber reinforced reactive powder concrete have been developed

andtested by edaTaha and Shrive (2003a,b) and Shaheen(2004) respectively.

2.4.7 FAILURE MODES OF ANCHORAGES- Various failure modeshave been observed

with wedge anchorages and FRP tendons, and these are summarized by separating them into

two main categoriesfailure of the anchorage system and rupture.

FIG 10 TYPES OF ANCHORAGE SYSTEMS

Failure of the anchorage system This kind of failure can be classified into four modes:

1. Movement or slip of the tendon out of the anchorage caused by insufficient grip (low shear

force) between the tendon and sleeve-Grip can be increased by increasing thefriction at the

contact surfaces, by increasing the normalforce applied, or both.

2. Slip of the sleeve and tendon together relative to the wedges-This indicates a high shear

force between thetendon and sleeve together with a lower shear force betweenthe sleeve and

wedges. This can be overcome in the samemanner as mentioned in 1.

3. Slip of the wedges relative to barrel-This rarely happens, mainly because of the design and

geometrical configuration of the wedges and the barrel. It is often accompanied

by crushing of the tendon.

4. Rupture of the rod inside the anchorage-High stress concentrations can be generated in the

tendon inside the anchorage, causing damage of the fibers. An anchorage design that results

in low stress concentration and uniform load distribution in the anchor overcomes this

problem.

Failure of the tendon outside the anchorage-If the tendon does not break in or

within three diameters of the anchorage, then the anchorage is not contributing to the failure

of the tendon and is considered a satisfactory anchorage design.

Stress Distribution in End Block-The end zone (or end block) of a post-tensioned

member is a flared region which is subjected to highstress from the bearing plate next to the

anchorage block. It needs special design of transversereinforcement. The design

considerations are bursting force and bearing stress. Unlike, in a pretensioned member, where

the prestress is transferred gradually, in a post-tensioned member, the stress is transferred at

the end. Hence, the end region of a post-tensioned member, which is called the end zone (or

the end block) is subjected to much higher stress concentration. To reduce the effect of stress

concentration for an I section, the end is made into a rectangular section by bearing the web,

so that the thickness at the end zone is much larger than the thickness of the web in the

intermediate region. Thus, the end zone of a post-tensioned member is usually a rectangular

section. This part of the rectangular section is carried over a certain distance within which

there is a high stress concentration. Beyond that end zone region, the width of the web is

reduced and for the intermediate region, it is narrowed down with the design width of the

web.

Fig:-11a Stress Distribution

This sketch helps us understand the effect of stress concentration, the cause and the effect of

stressconcentration in the end zone region. The bearing plate next to the anchorage block

applies theconcentrated stresses at the end of the member, yp0 is the dimension of the bearing

plate. After the stress is transferred to the concrete in this bearing region, the compressive

stress trajectories which are denoted by green lines, expand and over a certain length they

become parallel. It is assumed that the distance within which it becomes parallel is equal to

the larger dimension of the end zone. Thus, y0 is the larger transverse dimension of the end

zone within which the stress concentration effect gets reduced. Beyond y0, the stress

distribution is uniform, if the pre-stressing tendon is concentric and we do not have the effect

of stress concentration beyond the length y0.

Fig 11 b :- Stress Distribution

The end zone is divided into a local zone and a general zone. The local zone is a prism, right

behindthe bearing plate, it is subjected to very high stress concentration and to the tensile

stresses sigmat,which we take into account in designing reinforcement for the local zone. The

region outside the localzone is denoted as general zone. In fact, the local zone is considered

to be a part of general zone. Thegeneral zone also has stress concentration, but not as much as

the local zone but it has some othereffects, like spalling of concrete in the region outside the

bearing plate. The general zone is reinforcedby the end zone reinforcement to check the

bursting effect of the tensile stresses.Thus, the local zone is the region behind the bearing

plate and is subjected to high bearing stress and internal stresses. The behaviour of the local

zone is influenced by the anchorage device and the confining reinforcement.

The general zone is the end zone region which is subjected to spalling of concrete. It is

strengthenedby end zone reinforcement. We do provide special reinforcement in both the

local zone and generalzone region.

1.6 LOSSES IN PRESTRESSING

Losses of prestress are evaluated with reference to the initial tensioning stress in the steel

elements as existing upon anchorage to the prestressing bed. Thereforeprestress losses

include the contributions of elastic shortening, creep, shrinkage and relaxation In contrast, the

friction and anchorage losses which take place at the time of tensioning, are not considered.

Shrinkage: Shrinkage of a prestressed concrete member is taken to be the same as that of an

unstressed and unloaded companion member. In other, words shrinkage is defined to be

independent of stress. Furthermore in Section 30103 the restraining effect of longitudinal

steel is excluded from the shrinkage phenomenon. Hence shrinkage strain of a member is

defined to bethat of an unreinforced and unloaded companion member.

Creep: The time dependentstrain of concrete under sustained loading including both basic

creep and drying creep. In cases where the stressvarywith timethe instantaneous strain caused

by the change of stress is included in the elastic strain and is not considered a part of the

creep strain However the long term effect of the change of stress is included in creep .

Relaxation: The decrease of steel stress when subjected to a sustained strain Similar to the

creep strain the stress change which can be elastically calculated from the strain change is not

included in the relaxation. In other words relaxation is defined to be that portion of the

prestress loss which cannot be elastically related to the changes in strain so relaxation loss of

prestress is subdivided into two parts the initial relaxation loss occurring before transfer of

prestress and the long term relaxation loss occurring after transfer.

CHAPTER 2

FIBRE REINFORCED POLYMER FOR PRESTRESSING 2.1LITERATURE SURVEY

2.2 HISTORICAL DEVELOPMENT AND USE OF FRP

REINFORCEMENT

2.3 DESIGN GUIDELINES AND TECHNICAL COMMITTEES

2.4 RESEARCH EFFORTS

2.1 LITERATURE SURVEY

(REFER ACI440-04R) Fiber-reinforced polymer (FRP) composites have been proposed for use as prestressing

tendons in concrete structures. The promise of FRP materials lies in their high-strength

lightweight, noncorrosive, nonconducting, and nonmagnetic properties. In addition, FRP

manufacturing, using various cross-sectional shapes and material combinations, offers unique

opportunities for the development of shapes and forms that would be difficult or impossible

with conventional steel materials. Lighter-weight materials and preassembly of complex

shapes can boost constructibility and efficiency of construction.

At present the higher cost of FRP materials suggests that FRP use will be confined to

applications where the unique characteristics of the material are most appropriate.

Efficiencies in construction and reduction in fabrication costs will expand their potential

market. FRP reinforcement is available in the form of bars, grids, plates, and tendons. This

document examines both internal and external prestressed reinforcement in the form of

tendons.

One of the principal advantages of FRP tendons for prestressing is the ability to configure the

reinforcement to meet specific performance and design objectives. FRP tendons may be

configured as rods, bars, and strands as shown in Table. 1.1. The surface texture of FRP

tendons may vary resulting in bond with the surrounding concrete that varies from one tendon

configuration to another. Unlike conventional steel reinforcement there are no standardized

shapes, surface configurationsfiber orientation constituent materials and proportions for the

final products.

Similarly, there is no standardization of the methods of production, such as pultrusion,

braiding, filament winding, or FRP preparation for a specific application. Thus, FRP

materials require considerable engineering effort to use properly. Bakis (1993) has outlined

manufacturing processes. FRP tendons are typically made from one of three basic fibers.

These fibersareARAMID, CARBON, AND GLASS. Aramid fibers consist of a semi

crystalline polymer known as aromatic polyamide. Carbon fibers are based on the layered

graphene (hexagonal) networks present in graphite while glass generally uses either E-glass

or S-glass fibers. E-glass is a low-cost calcium-alumino-boro-silicate glass used where

strength, low conductivity, and acid resistance are important. S-glass is a magnesium-

alumino-silicate glass that has higher strength, stiffness, and ultimate strain than E-glass. S-

glass costs more than E-glass, and both are susceptible to degradation in alkaline

environments. Table 1.1 gives properties of typical fibers.

The selection of the fiber is primarily based on consideration of cost, strength, stiffness, and

long-term stability. Within these fiber groups different performance and material

characteristics may be achieved. For example aramids may come in low, high, and very high

modulus configurations. Carbon fibers are also available with moduli ranging from below

that of steel to several multiples of that of steel. Of the several fiber types glass-based FRP

reinforcement is least expensive and generally uses either E-glass or S-glass fibers. The resins

used for fiber impregnation are usually thermo setting and may be polyestervinylester epoxy

phenolic, or polyurethane.

The formulation, grade, and physical-chemical characteristics of resins are practically

limitless. The possible combinations of fibers, resins, additives, and fillers make

generalization of the properties of FRP tendons very difficult. Additionally FRP composites

are heterogeneous and anisotropic. Final characteristics of an FRP tendon are dependent on

fiber and resin properties, as well as the manufacturingprocess. Specific details of a particular

tendon should beobtained from the manufacturer of the tendon.

Table 1.1 Fiber Properties

2.2 HISTORICAL DEVELOPMENT AND USE OF FRP REINFORCEMENT

(REFER ACI440-04R)

The concept of using short glass fiber reinforcement in concrete was first introduced in the

1930s but was not developed into long fiber reinforcement for nearly two decades. In the

1950s and 1960s the U.S. Army Corps of Engineers was sufficiently interested in long glass

fibers for reinforcement that a series of comprehensive reports was compiled (Mather and

Tye 1955Pepper and Mather 1959; Wines, Dietz, and Hawley 1966). Although these reports

were generated research and site applications were limited. In the 1970s, corrosion-induced

deterioration of concrete structures, particularly bridge decks, led to a renewed interest in

designstrategies that would reduce susceptibility of structures to corrosive environments. In

the 1970s, research activities started in Germany on glass FRP-based prestressing tendons.

In 1978, a joint venture between German contractor Strabag-Bau and German chemical

producer Bayer resulted in glass fiberreinforced polymer (GFRP) tendons and an anchorage

system for post-tensioning applications. These tendons were incorporated in several bridges

in Germany and Austria. After various transition stages however, Strabag stopped its

activities in this field in the early 1990s. The National Bureau of Standards (NBS)now

renamed the National Institute of Standards and Technology (NIST) examined non-metallic

rods for antenna guy wires. In the process, theyconducted some of the first research into

anchorage of composite rods that became relevant to prestressed concrete application of FRP

materials (NBS 1976). Interest in the corrosion-resistant properties of non-metallic bars and

tendons continued to grow in the 1980s. In 1983, AKZO, a chemical producer in the

Netherlands, and HBG, a contractor, jointly developed aramid fiber reinforced polymer

(AFRP) prestressing tendons. The Japanese have also undertaken an extensive national

program to examine the use of FRP reinforcement in concrete structures. Around 1980,

research and development began in Japan on production techniques for FRP reinforcement

and its application to concrete structures.

This research and development originally focused on the development of FRP-reinforced

concrete members that used FRPs instead of steel reinforcing bars andprestressing tendons. In

the United States, a new anchorage was developed for glass fiber tendons (Iyer and

Kumarswamy 1988), and the prestressing use of Kevlar was investigated (Dolan 1989). Iyer’s

anchorage was supported financially by the Florida Department of Transportation (FDOT),

which funded a major study to investigate the prestressing application of glass fiber tendons

for bridge and marine substructures (Sen,Issa, and Mariscal 1992).

This research culminated in the first conference to focus on FRP composites for civil

engineering applications (Iyer and Sen 1991), and the construction of the first FRP

prestressed bridge in RapidCity, South Dakota (Iyer 1993). These similar efforts led to the

development of several commercial tendon systems, many of which are discussed in the

proceedings of the First International Symposium for FRP in Reinforced Concrete Structures

(FRPRCS-1) (Nanni and Dolan 1993), and in a Japanese Society of Civil Engineers

publication (JSCE 1996).

2.3DESIGN GUIDELINE AND TECHNICAL COMMITTEES

(REFER ACI440-04R) In 1993, the first design guidelines for FRP-reinforced and prestressed concrete buildings

were established by the Japanese Society of Civil Engineers. The Japanese version of the

guideline was released in 1995, while the English version (Sonobe et al. 1997) was published

in 1997. The Canadian Standards Association has produced two standards CAN/ CSA S6-00

and CAN/CSA S806-02 that contain code provisions for the use of FRP prestressing tendons

in bridges and buildings respectively. In Europe, unified design guidelines for FRP

reinforcement are under development. A task group with this aim was established at the end

of 1996, within the former CEB (Euro-International Concrete Committee). In December

1997, a 4-year training and mobility of researcher’s network project titled “Development of

Guidelines for the Design of Concrete Structures, Reinforced, Prestressed or Strengthened

with Advanced Composites,” started. This so called “ConFiber-Crete Network” was

comprised of 11 teams from nine different European countries. Since the merger of CEB and

FIP (Federation Internationalede la Precontrainte), this task group has been integrated in the

new fib(Federation Internationale du Béton). Task Group 9.3 of fibCommission 9 is charged

with developingdesign guidelines for concrete structures reinforced, prestressed, or

strengthened with FRP, based on the designformat of the CEB-FIP Model Code and

Eurocode 2 (fibTG9.3). Recent activities in Europe have been summarized by Matthys and

Taerwe (2001).

The American Society of Civil Engineers (ASCE) establisheda standards committee to

address standalone FRP products.The Transportation Research Board (TRB) has formally

established Committee A2C07 to examine the use of FRP in bridge structures. Other societies

including the Society for the Advancement of Material and Process Engineering (SAMPE)

and the Market Development Alliance (MDA) of the FRP Composites Industry have been

active in the area of FRP for construction use.

2.4RESEARCH EFFORTS

(REFER ACI440-04R) Early development work on prestressing with FRP was carried out at the South Dakota

School of Mines by Iyer who developed the first prestressing anchorage in the late 1980s.

The first glass fiberprestressed bridge built in the United States was in Rapid City, South

Dakota, in 1990. Other research was carried out at the University of South Florida, Florida

Atlantic University, and the Florida Department of Transportation (Sen, Issa, and Mariscal

1992).

Studies included static and fatigue testing of beams and half-scale bridges durability studies

and full-scale testing of piles. All three materials- aramid, carbon, and glass were evaluated.

Work relating to FRP prestressing in the United States has been documented by Dolan

(1999). Much of the research on FRP reinforcement in the United States has been conducted

by individual investigators at the University of Arizona(Eshani, Saadatmanesh and Nelson

1997), the University of Michigan (Naaman and Jeong 1995), the Massachusetts Institute of

Technology (Triantafillou and Deskovic 1991), Pennsylvania State University (Nanni et al.

1996a,b), South Dakota School of Mines (Iyer et al. 1996), the University of California (Long

Beach),

West Virginia University (Vijay and GangaRao 2001), the University of Wyoming (Dolan et

al. 2000), and Lawrence Technological University (Grace 2000a,b). In 1993 FHWA

sponsored research into acceleratedaging and standardized testing of FRP materials at

Georgia Institute of Technology, Pennsylvania State University, and the Catholic University

of America. In 1994, FHWA sponsored research into development of design

recommendations for FRP prestressing for bridge girders that led to design specification

recommendations for AASHTO (Dolan et al. 2000). Lawrence Technological University has

developed a demonstration bridge using external unbonded FRP tendons (Grace 1999). In

Canada, several researchers mostly within ISIS Canada (Canadian Network of Centers of

Excellence on Intelligent Sensing for Innovative Structures), have been investigating

applications of FRP prestressing tendons. Work at the University of Manitoba has

emphasized carbon FRP tendons and has considered the behavior of prestressed beams

underboth service and ultimate conditions (Abdelrahman, Tadros, and Rizkalla 1995; Fam,

Rizkalla, and Tadros 1997). Extensive studies on bond and transfer length have also been

conducted. At the Royal Military College of Canada (RMC), work has been done on aramid

FRP tendons (McKay and Erki 1993), and more recently on carbon FRP tendons.

Researchers at Queen’s University have been investigating the low temperature and long-

term behavior of beams prestressed with CFRP (Bryan and Green 1996). Additionally the

possibility of using CFRP rods to prestress bridge deck slabs was investigated (Braimah,

Green, and Soudki 1996), and work on the transfer length of beams prestressed with carbon

FRP was conducted (Soudki, Green, and Clapp 1997). Partially prestressed, partially bonded

FRP tendons have been investigated (Rizkalla, Fang, and Campbell 2001). Noncorrosive

wedge-type anchorages for FRP tendons have been developed at the University of Calgary

(Sayed-Ahmed and Shrive 1998; Campbell et al. 2000; Shaheen 2004). At the University of

Sherbrooke, extensive investigations are being conducted into the durability of FRP rods for

reinforcing and prestressing concrete, and into the development of a bond-type anchorage

(Zhang 2002).

The effects of temperature on beams prestressed with FRP tendons have been the focus of

research at Concordia University and applications of unbonded FRP tendons have been

considered at the University of Windsor (Salib, Abdel-Sayed, and Grace 1999). Researchers

at Carleton University and the University of Waterloo are also investigating applications of

FRP prestressing tendons. The decline in the Japanese economy in the 1990s slowed the

Japanese development program and has curtailed the availability of many Japanese products

for evaluation and testing in North America.

Developments in Japan have been addressed by Fukuyama (1999), and details of some recent

projects are available from the Advanced Composites Cables(ACC) Club. Activities in

Europe relating to the use of FRP have been reported by Taerwe and Matthys (1999). Of the

projects financially supported by the European community, the BRITE/EURAM project,

“Fiber Composite Elements and Techniques as Non-Metallic Reinforcement for Concrete,”

started November 1991 and ended in 1996. The Universities of Braunschweig and Ghent

together with industrial partners from Germany and The Netherlands, investigated

performance characteristics and structural aspects of FRP reinforcement for prestressed and

reinforced concrete members.

The EUROCRETE project, a Pan-European collaborative research program with partners

from the United Kingdom, the Netherlands, Switzerland, France, and Norway, began in

December 1993 and ended in 1997. This project included material development, research on

durability in aggressive environments, determination of structural behaviour, and

development of design guidance, techno-economic, and feasibility studies. The project

included construction of demonstration structures.

CHAPTER 3

DESIGN CRITERIA

3.1 DESIGN OF PRESTRESS BEAM

3.1.1) USING STEEL.

3.1.2) USING CFRP.

3.2 CALCULATION OF LOSSES

3.2.1) FOR STEEL.

3.2.2) FOR CFRP.

3.3 ANCHORAGE DESIGN

3.1.1 DESIGN OF BEAM WITH STEEL TENDON Depth, d 300 mm

Breadth, b 200 mm

Length, L 3 m

Eccentricity, e 100 mm

Characteristic Strength of Concrete, fck 50 N/mm2

fy 415 N/mm2

fp 1860 N/mm2

200 mm 3 m

300 mm EFFECTIVE DEPTH FOR STEEL BARS:

Effective Cover 30 mm

Effective Depth 270 mm

EFFECTIVE DEPTH FOR TENDON:

Effective Cover 50 mm

Effective Depth 250 mm

TENDON DIAMETER & AREA:

Diameter of tendon 6 mm

Assume Ap (using 3 bars) 84.8571 mm2

CALCULATION OF AST:

0.85 = Ast Ast = (0.85 x bd)

fy bdfy

= 0.85 x 200 x 300= 110.602 mm2

` 415

DEPTH OF NEUTRAL AXIS:

Compressive Force = Tensile Force

0.36 fck b Xu = fpAp + 0.87 fyAst

Xu = fpAp + 0.87 fyAst

0.36 fck b

Xu = 54.935 mm

From, Apfp/(bdfck) = 0.063

Now, using Table 11 ( IS : 1343 - 1980 )

fpu = 0.87 x fp = 0.87 x 1860

fpu = 1618.2 N/mm2

CALCULATION OF PRESTRESSING FORCE, P:

• ftt = -(4.8 + 0.55x3) = -6.45 N/mm2 ( from Table 8 – IS :1343-1980)

• fct = 0.4266fck = 21.33 N/mm2 ( from Fig. 8A – IS :1343-1980)

• fsup = ftt – Mg/Zt = -7.0215 N/mm2

• finf= fct + Mg/Zb = 21.8925 N/mm2

• P = A (finfZb + fsupZt) = 446.128 KN

(Zb + Zt )

• e = Z (finf – fsup) = 97.216 mm

A (finf + fsup)

MOMENT CALCULATION:

• MOMENT DUE TO DEAD LOAD:

wg = 24 x 0.2 x 0.3 = 1.5 KN/m

Mg = wg L2/8 = 1.6875KNm

• MOMENT DUE TO TENDON:

M1 = fpuAp( d – 0.42 Xu ) = 31.16 KNm

• MOMENT DUE TO AST:

M2 = 0.87 fyAst( d - 0.42 Xu) = 9.86 KNm

• TOTAL MOMENT OF RESISTANCE:

MR = M1 + M2 = 41.012 KNm

• CALCULATION OF LOAD:

Equating, MR = Mg + ML where, ML=

wuL/3 wu = 39.33 KN

Safe Load, w = wu /1.5

= 26.22 KN

3.1.2 DESIGN OF BEAM WITH FRP TENDON

Depth, d 300 mm

Breadth, b

200 mm

Length, L

3 m

Eccentricity, e

100 mm

Characteristic Strength of Concrete, fck

fy

fpu

50 N/mm2

415 N/mm2

2100 N/mm2

200 mm 3 m

300 mm

Stress Curve for FRP Tendon

CALCULATION OF AP: FOR BALANACED SECTION

Compressive force = Tensile force

0.85 fckβ1 cb = ρbdfpu

ρb = 0.85β1fck c

fpu d

= 0.85 β1fckxεcu

fpuεcu + εpu– εpe

= 0.002398003

Hence, Ap = 143.88 mm2

Depth of N.A.: For balanced section Assumed Ap = 96.5 mm2 (4#6.4mm)

c = Ap fpu+0.87fyAst = 54.6875 mm c = 43.906 mm

0.85 fck β1 b Depth of compression block, a = β1 c = 28.593 mm

EFFECTIVE DEPTH FOR TENDON: Cover 50 mm

Effective Depth 250 mm

EFFECTIVE DEPTH FOR STEEL BAR:

Cover 30 mm

Effective Depth 270 mm

MOMENT CALCULATION:

• Moment due to FRP tendon:

Mn = Apfpu (d - a/2) = 47.77 KNm

Strength reduction factor for CFRP, φ = 0.85 (From ACI 440.4R-04)

φMn = 40.605KNm

• Moment due to Steel bar :

M = 0.87 fyAst (d – 0.42 Xu) = 10.0455KNm

• Total Moment of Resistance:

MR = φMn + M = 50.65KNm

Table 3.1.1 - CONDITIONS AT THE ULTIMATE LIMIT STATE FOR RECTANGULAR BEAMS WITH PRE-TENSIONED TENDONS OR WITH POST-TENSIONED TENDONS

HAVING EFFECTIVE BOND

Table 3.1.2 - HYPOTHETICAL FLEXURAL TENSILE STRESSES FORTYPE 3 MEMBERS

3.2.1LOSSES CALCULATION FOR STEEL

Design Data:- Eccentricity of the tendons(e) 100mm.

Initial Pre stress load(Po) 446 kN/mm2

Length of span(L) 3m.

Modulus of Elasticity of Steel(Es) 210kN/mm2

Modulus of Elasticity of Concrete (Ec) 35kN/mm2

Relation of steel stress 5% of initial stress

Coefficient of creep(∅) 1.6 Slip Shrinkage 1 mm

Friction Coefficient (Ø) 0.0015 per m

Calculation:-

Prestressing Force = 446kN

Area of section = 300× 200

=6× 104 mm2

Modular ratio(α) = Es/Ec

=6

Moment of inertia = bd3/12

= 200× (300)3/12

= 45×106 mm4 Stress in concrete

Fc= (446×103/6×104 ) + (446×103×100×100/45× 107) = 17.22N/mm2

Calculation of Losses:-

1. Elastic deformation of concrete

a) Pretension beam

= α×fc

= 6× 17.22 =132.45 N/mm2

2. Relaxation of stress in steel

a) Pretension & Posttension

= 5% of initial stress

= 5×5255.89/100 = 262.79 N/mm2

3. Loss due to creep

a) Pretension & Posttension

Ø×fc×α

= 1.6×17.22×6 = 211.9 N/mm2

4. Shrinkage of concrete

a). Pretension

=300×10-6× Es

= 300 × 10-6× 210 ×103

= 63 N/mm2

b). Post Tension

=200 × 10-6× Es

= 200 ×10-6× 210 ×103

= 42 N/mm2

5. Slip of anchorage

P/A = EsΔ/L

Δ = (210 ×103×1)/(3000) = 70 N/mm2

6. Friction loss

P0(µα×kx)

From IS-1343 µ = 0.55

Equation for the parabolic tendon is :-

y = 4e/L2x(L-x)

α= dy/dx

α= 4e/L (Calculating on starting point, x=0)

α = 0.133

µα = .055× .133 = 7.33× 10 -3

Kx= 0.0015 × 10 = 0.015

Loss due to friction = 1000 (7.33× 10-3 +0.015) = 54.2 N/mm2

Total loss in Pretension beam:

= ES+RS+CR+SR

= 133.8+262.7+214.08+63

= 673.58 N/mm2

Percentage loss =673.58×100/5255.89 = 12.75%

Total Loss due to Posttension beam

= RS+CR+SR+SA+FR

= 262.79+214.08+42+70+54.2

=642.98 N/mm2

Percentage Loss = 642.98× 100/5255.89 = 12.19%

3.2.2 LOSS OF PRESTRESS IN CFRP

Design Data :- Eccentricity of the tendons(e) 100mm.

Initial Pre stress load(Po) 446 kN/mm2

Length of span(L) 3m.

Modulus of Elasticity of Steel(Es) 210kN/mm2

Modulus of Elasticity of Concrete (Ec) 35kN/mm2

Relation of steel stress 5% of initial stress

Coefficient of creep(∅) 1.6 Slip Shrinkage 1 mm

Friction Coefficient(Ø) 0.0015 per m

Moment due to dead load 71.7 Nm

Calculation :-

Prestressing Force = 446 KN Area of section = 300× 200

=6× 104 mm2

Modular ratio(α) = Es/Ec =6

Moment of inertia = bd3/12

= 200× (300)3/12

= 45×106 mm4 Stress in concrete

Fc=(446×103/6×104 ) + (446×103×100×100/45× 107)-(71.7*100/6*104) = 17.344N/mm2

Calculation of Losses:-

1. Elastic deformation of concrete

a) Pretension beam

= α×fc

= 6×17.34 =67.30 N/mm2

2. Relaxation of stress in steel

a) Pretension & Posttension

= 3% of ultimate tensile strength of tendon

= .03×5255.89 = 157.67N/mm2

3. Loss due to creep

a) Pretension & Posttension

Ø×fc×α

= 1.6×17.34×6 = 134.61 N/mm2

4. Shrinkage of concrete

a). Pretension

=300×10-6× Es

= 300 × 10-6× 137.2×103

= 82 N/mm2

b). Post Tension

=200 × 10-6× Es

= 200 ×10-6× 137.2×103

= 76 N/mm2

5. Slip of anchorage

P/A = EsΔ/L

Δ = (137.2×103×1)/(3000) = 45.73 N/mm2

6. Friction loss

P0(µα×kx)

From IS-1343 µ = 0.55

Equation for the parabolic tendon is :-

y = 4e/L2x(L-x)

α= dy/dx

α= 4e/L (Calculating on starting point, x=0)

α = 0.133

µα = .055× .133 = 7.33× 10 -3

Kx= 0.0015 × 10 = 0.015

Loss due to friction = 1000 (7.33× 10-3 +0.015) = 5.42 N/mm2

Total loss in Pretension beam :

= ES+RS+CR+SR

= 157.67+67.3+134.61+82

= 441.58 N/mm2

Percentage loss =441.58×100/5255.89 = 8.401 %

Total Loss due to Posttension beam

= RS+CR+SR+SA+FR

= 157.67+67.3+134.61+82+45.733+54.2

=492.733 N/mm2

Percentage Loss = 492.733× 100/5255.89 = 10.31%

3.3ANCHORAGE DESIGN

Bursting Tension formula :

According to IS-1343:

Fbst =P[0.32-0.3(ypo/yo)]

Where,

P = anchorage force

Ypo/yo= distribution ratio

2ypo = depth of the anchorage plate

2yo = depth of the equivalent prism DESIGN PROCEDURE

P = 446 KN

2ypo = 100 mm

2yo =300 mm

Ypo/yo = 0.33

P = 446 KN

2ypo = 100 mm

2yo =300 mm

Ypo/yo = 0.33

Bursting Tension, Fbst

= P[0.32-0.3(ypo/yo)] =446x103[0.32-0.3(0.33)]

= 98120 N

CHAPTER 4

ANALYSIS RESULTS FROM ANSYS

4.1Model Prepared in Ansys

4.1 DEFORMATION DUE TO PRESTRESSING FORCE

4.3STRESS DISTRIBUTION IN BEAM

4.4MOMENT IN THE BEAM

4.5ANCHROGE PORTION OF THE BEAM

CONCLUSION OF THE PROJECT

This report introduce the use of CFRP in the prestress beam as a tendon.

The final conclusion is based on the obtained data from the calculation of losses and

information given in ACI440-04r.

Losses Pre Tension Post Tension

Material Steel C.F.R.P Steel C.F.R.P

Elastic

Deformation

133.80N/mm2 67.307N/mm2 N/A N/A

Relaxation Of

Stress

262.70N/mm2 157.67N/mm2 262.79N/mm2 127.31N/mm2

Creep 214.08N/mm2 134.61N/mm2 214.08N/mm2 134.61N/mm2

Shrinkage 63N/mm2 82N/mm2 42N/mm2 82N/mm2

Anchorage

Slip

N/A N/A 70N/mm2 45.73N/mm2

Friction N/A N/A 54.2N/mm2 5.420N/mm2

Total Loss 12.81% 8.401% 12.24% 10.31%

TABLE 3 -COMPARISION ON THE BASIS OF LOSSES:-

So on the basis of this results we can conclude that the CFRP have less loss in prestressing

over steel tendons as a result we have to apply less prestressing force as compared to steel

tendons.

TABLE 4 - CONCLUSION ON THE BASIS OF ACI440-04R

Typical Uniaxial Tensile Properties of Prestressing Tendons (CAN/CSA-S806-02)

Mechanical Properties Prestressing

Steel

AFRP

Tendon

CFRP

Tendon

GFRP

Tendon

Nominal yield stress

(MPa)

1034−1396 N/A N/A N/A

Tensile strength (MPa) 1379−1862 1200−2068 1650−2410 1379-1724

Elastic Modulus (GPa) 186−200 50−74 152−165 48-62

Yield Strain (%) 1.4−2.5 N/A N/A N/A

Rupture Strain (%) >4 2−2.6 1−1.5 3-4.5

Density (kg/m3) 7900 1250−1400 1500−1600 1250-2400

According to this table we can observe that the density of CFRP is very much less than steel

so due to this the dead load of the beam will get reduce and cost will also come down.

Also the tensile strength of CFRP is higher than the steel tendons so because of that CFRP

can resist more load as compared to Steel

CONCLUSION BASED ON CHARACTERISTIC

• CFRP is non corrosive in nature so can be used in underground construction for better

factor of safety.

• CFRP is non-magnetic so it can be used in the high magnetic field like labs.

REFERENCES:-

1. ACI 440-04r (For Designing FRP Tendons)

2. ACI 440-06r(For FRP Properties)

3. ACI 440-01r (For FRP Anchaorage)

4. IS: 1343-1980 (For Prestressing Steel)

5. FRP tendon anchorage in post-tensioned concrete structures

J.W. Schmidt & B. TäljstenTechnical University of Denmark, Kgs. Lyngby, Denmark

A. BennitzLuleå University of Technology, Luleå, Sweden

J.W. Schmidt & H. PedersenCOWI A/S, Lyngby, Denmark

6. Prestress losses tihuang

7. Prestress Concrete by N.KrishnaRaju (For Design Procedure).

8. Anchoring Method For Prestressing Of FRP reinforcement

D Ďurech, Brno University of Technology, Czech Republic

F Girgle, Brno University of Technology, Czech Republic

D Horák, Brno University of Technology, Czech Republic

I Laníkovcá, Brno University of Technology, Czech Republic

P Štěpánek*, Brno University of Technology, Czech Republic

9. Design Recommendations For Concrete Structures Pre-stressed With FRP

Tendons,Final Report August 1, 2001 Prepared by University of Wyoming Charles W.

Dolan H.R. Hamilton III Pennsylvania State University Charles E. Bakis And

University of Missouri - Rolla Antonio Nanni

10. Google and Wikipedia (For Graphs and Images).