REHABILITATION SOLUTIONS FOR EXISTING STRUCTURES IN ROMANIA

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REHABILITATION SOLUTIONS FOR EXISTING

STRUCTURES IN ROMANIA

Sorin Dan1 : 69.059.25:631.24

DOI:10.14415/konferencijaGFS 2015.015

Summary: The paper deals with aspects regarding strengthening of reinforced concrete

existing structures in seismic zones, like Romania. Some case study and the

rehabilitation of characteristic structures are analysed. The rehabilitation solutionswere chosen in accordance with the actual stage of building deterioration as well as

function of the actions characteristics. Classic (reinforced concrete and/or steel) and

modern (Carbon Fibre Reinforced Polymers) materials and technologies for

strengthening have been used.

Keywords: Existing reinforced concrete structures, seismic action; strengthening;

classic rehabilitation solutions; modern rehabilitation techniques; carbon fibre

reinforced polymers (CFRP)

1. INTRODUCTIONThree strengthening solutions will be analyzed in the paper. The strengthened elements

are existing reinforced concrete columns as vertical structure of different constructions.

The rehabilitation solutions are:

steel bracing with four angle steel shapes connected by flange plates;

carbon fibre polymer composites (CFRP): longitudinal strips and transversal wraps;

jacketing by reinforced concrete using longitudinal reinforcement bars andtransversal stirrups.

2. REHABILITATION OF REINFORCED CONCRETE SILOS

The assessment and rehabilitation solutions for a group of silos owned by the SAB

Miller Brewery Company Timisoreana are presented. The silos (Figure 1) were built40 years ago and stand 28 m high and 7.30 m in diameter.

1Sorin Dan, Lect.Dr.Civ.Eng., University Politehnica Timisoara, Department of Civil Engineering andInstallations, Str. T. Lalescu, No. 2, Timisoara, Romania, tel: +40256403933, e mail: [email protected]


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Contemporary achievements in civil engineering 24. April 2015. Subotica, SERBIA

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Figure 1. Reinforced concrete silos Figure 2. Reinforcement corrosion

of discharge funnel supporting

columns

Initial silos inspection (1999) revealed

large zones of circular cells with concrete

cover dislocated and corrosion of

circumferential steel reinforcement.

Recent silos inspection and assessment(2004) emphasized other vulnerable parts:

infrastructure and charging platform

(gallery).

The silos infrastructure consists offoundation raft, discharge funnel and its

supporting columns and beams.

The main damages are due to water

infiltration and high humidity inside of

each cell bottom part, which caused

important dislocated concrete cover and

corrosion of the columns steelreinforcement (Figure 2).

The strengthening of supporting columns

for the discharge funnel consists of steel

profiles (Figure 3). This solution has a

smaller cost than CFRP materials. On the

other hand, steel profiles have a better

buckling behaviour than CFRP strips. ConexpandM12/120/30

L60X60X6L=4000mm

L 80x80x8

L 80x80x8

40x5...295

40x5...295

Conexpand

M12/120/30

Figure 3. Strengthening solution with steel

profiles


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3. REHABILITATION OF A FRAMED BUILDING

The Western University of Timisoara has

many buildings, among them the Main

Building (Figure 4 and 5) that is used as

administrative part as well as classrooms

for students, was built in 1962-1963.

The RC structure consists of:

transversal and longitudinal frameswith eight storeys and two spans of

5.6 m and eleven bays of 3.8 m;

floors with girder mesh in two

directions and a slab of 10 cm; foundation with a thick slab and deep

beams in two directions.

Figure 4. The Western University of

Timisoara

3.90

Strengthened columns at the first storey

Legend:

5.

60

1

5.6

0

Stairs

3.80 3.80 3.80 4.00 3.80 3.80 3.80 3.80 3.80 3.90

2 123 4 5 6 7 8 9 10 11

A

B

C

SC 1 SC 2 SC 3 SC 4 SC 5 SC 6 SC 7 SC 8 SC 9 SC 10 SC 11 SC 12

SB 1 SB 2 SB 3 SB 4 SB 5 SB 6 SB 7 SB 8 SB 9 SB 10 SB 11 SB 12

SA 1 SA 2 SA 3 SA 4 SA 5 SA 6 SA 7 SA 8 SA 9 SA 10 SA 11 SA 12

Figure 5. Framing plan ground storey

On examination of the building and from non-destructive measurements no important

damages of the RC structure were noticed. Some local damage due to incipient

reinforcement corrosion was detected at the columns of the ground storey.

The analysis of the structure has been performed at both combinations of actions:

fundamental combinations and special combinations including seismic action at present-

day level. From the analysis it was noticed:

weakness of reinforcement and insufficient anchorage of beam-positivereinforcement at the beam-column joint, especially in the longitudinal direction;

the drift limitation conditions are not within the admissible limits at the groundstorey.

Rehabilitation solution consists in strengthening of the columns located at the ground

storey (Figure 6 and 7): some columns were strengthened in 1999 to prevent the local

damages due to reinforcement corrosion; the other columns were rehabilitated in 2004


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for decreasing the lateral displacements (drift limitation conditions) and for a

homogeneous columns stiffness at the ground storey.

SB1,

12

550

900

100x10...900

100x10...550

100x10...550L100x100x10...5130

100x10...900

Figure 6. Strengthening solution with steelprofiles

Figure 7. Rehabilitation solution ofcolumns

4. REHABILITATION OF A MASONRY BUILDING

The "Palace" structure (Figure 8) is a huge building (underground floor, ground floor -

restaurant, 3 storeys - apartments, timber roof), built before 1900's with a composite

structure: masonry and reinforced concrete framed structure (Figure 9).

Figure 8. The "Palace" building Figure 9. Longitudinal reinforced concrete

frames

Initially it was an entire masonry structure, but later the ground floor was changed: some

resistance brick walls were cut and two longitudinal RC frames were erected to sustain

all the vertical loads. Due to this architectural operation the structure became more

vulnerable at seismic actions: by the transversal direction main part of the ground floor

became unstable at horizontal actions because of some erected columns with hinge


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connection at both ends (masonry wall supports from the underground floor and ground

storey). Other vulnerabilities of the building consist of: overall lateral stiffness valuesalong the two main axes are different; lack of seismic joints to divide building parts

having different dynamic characteristics; lack of straps at each floor.The building assessment emphasized some aspects: concrete quality is very variable in

structural elements, having different classes (C8/10 - C16/20); some cracks in

longitudinal beams; corrosion of the slab reinforcement; etc.

From the static and dynamic analysis a very important conclusion could be drawn: the

earthquake capacity ratios R between the actual values of ultimate bending moment

(Mcap) and the necessary bending moment (Mnec), given by the present-day seismic action

level, were very low for columns. That meant that the building was characterized by a

high risk of collapse at seismic actions. It resulted the necessity of structural

rehabilitation.

In accordance to the structural analysis, the strengthening of the ground floor was chosen

in order to obtain technical and economical advantages: safe behaviour at seismic

actions; slight change of the overall structural stiffness; easy strengthening technology

and short period of refurbishment (December 2004 - June 2006).

The strengthening have been made on the

following structural elements:

strengthening by RC coating (7 cm oneach side) of masonry walls from the

underground floor of the building;

new reinforced concrete floor withembedded steel profiles (HEB 220) intwo directions, which stands as beams

for the new structure;

Figure 10. Strengthening of columns

strengthening of half from the existing columns (60x60m coated by RC to become90x90cm Figure 10) and erecting of new transversal RC beams in order to createnew transversal frames (Figure 11);

strengthening by RC coating of existing longitudinal beams;

rehabilitation of some structural elements having corroded reinforcement.


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GLC 90x90GLC 90x90

GLB 90x90GLB 90x90

GLA 75x90 GLA 75x90

1,92

3,39

3,5

0,47 3,18 0,63,470,9

3,490,9 0,48

1,46

3,

06

0,3

9

1,741,61 3,2

0,6

3,35

0,61

0,46 3,57

5,9

3

5,9

3

5,9

3

3,390,94,720,644,840,9

4,124,15

0,6

0,6 0,38 1,5 0,4 0,63 3,51

4,71

0,8

4

4,66

0,6

5,1

2

0,6

0,9

4,9

4

0,6

0,62

1,9

4

0,9

1

1,86

0,6

0,

6

5

2,7

9

11

,53

3,57

1,

44

0,4

3,26

0,

7

1,

44

S290x9090x90

S2 S290x90

90x90 S1 S1

90x90 S190x90

S190x90strengthened at 90x90cm

Existent longitudinal beam 60x80cm

GT3-90x80

GT2-90x80

NEWB

EAM

GT1-90x80

NEWB

EAM

NEWB

EAM

GT3-90x80

NEWB

EAM

GT2-90x80

NEWB

EAM

GT1-90x80

S190x90

S190x90

strengthenedat90x80cm

Existentbeam60x45cm

strengthened at 90x90cmExistent longitudinal beam 60x80cm

strengthened at 75x90cm

Existent longitudinal beam 60x60cm

Figure 11. Ground floor rehabilitation

5. CONCLUSIONS

The main ideas which may emerge from these studies are:

a) As structural rehabilitation for existing reinforced concrete structures severalstrengthening solutions may be used: steel bracing; carbon fibre polymer composites

(CFRP); jacketing by reinforced concrete.

b) The manufacture time is shorter in case of using CFRP in comparison to classicstrengthening solutions (steel bracing or reinforced concrete jacketing).

c) The cost of CFRP solutions for strengthening is higher than other solutions.d) Using of CFRP solution for strengthening of columns may be inadequate in case of

structural stiffness increase demands.

REFERENCES

[1] fib Bulletin 14, Externally Bonded FRP Reinforcement for RC Structures, fib,Lausanne, 2001.

[2] Ghobarah, A.: Seismic assessment of existing RC structures.Progress in StructuralEngineering and Materials, 2000, Vol. 2, No. 1.

[3] Bob, C., Dan, S.: Analysis, Redesign and Rehabilitation of Reinforced ConcreteFramed Structures in Seismic Regions, fib Symposium: Concrete Structures in

Seismic Regions, Athens, 2003.

[4] Bob, C., Dan, S., Badea, C., Iures, L.: Classic and Modern RehabilitationTechniques in Seismic Zones, IABSE Symposium: Structures and Extreme Events,

Lisbon, 2005.

[5] Dan, S., Bob, C., Gruin, A.: Analysis of Reinforced Concrete Existing Structures inSeismic Regions, WSEAS International Conference: Engineering Mechanics,

Structures, Engineering Geology EMESEG08, Heraklion, Greece, 2008.


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[6] Bob, C., Bob, L.: Sustainability of New and Strengthened Buildings, WSEAS

International Conference on Sustainability in Civil Engineering SSE09, Timisoara,Romania, 2009.

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REHABILITATION SOLUTIONS FOR EXISTING STRUCTURES IN ROMANIA