1E7 Rehabilitation VS 1.pdf

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Rehabili tation and Maintenance of Buildings

Valeriu STOIAN

Lecture : 19/06/2014 – 8.30-10.00/10.30-12.00

European Erasmus Mundus Master Course

Sustainable Constructions

under Natural Hazards and Catastrophic Events520121-1-2011-1-CZ-ERA MUNDUS-EMMC


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L10 – B.2 – Mechanical properties of cast iron, mild iron and steel at historical structures


Sustainable Constructions under Natural

Hazards and Catastrophic Events

PART A – STRUCTURAL REHABILITATION USING CFRP

FIBER - carbon- glass- aramid- hybride

RESIN - thermoplast

- thermorigide

COMPOSITE (FRP)(polymers reinforced with fiber)

COMPOZITES ?


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Sustainable Constructions under NaturalHazards and Catastrophic Events


FRP TYPES

1. STRENGTHENING

- FABRIC

- LAMELAS (STRIP)

- REINFORCEMENT


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2. REINFORCEMENT → IN CONCRETE

FPR TYPES


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3. PROFILE

FPR TYPES


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4. SANDWICH PANELS

TYPES


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APPLIED ON THE ELEMENT SURFACE

STRENGTHENING WITH COMPOSITES


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• HIGH STRENTHG (10x steel)

• LESS WEIGHT (1/4 of steel)

• VERRY THIN

• DURABIITY

• NO MAINTENANCE

• HUGE VARIETY OF SYSTEMS

• FAST EXECUTION

• IMPACT RESISTENCE

• THE MATERIAL PROPRIETIES AS A STRUCTURE

ADVANTAGES OF THE STRENGTHENING WITH COMPOSITES


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DESADVANTAGIES OF COMPOSITE STRENGTHENING

• LOW FIRE RESISTENCE

• MECHANICAL DETERIORATION

• ULTRAVIOLET DEGRADATION

• SMALLER LIMIT STRAIN AT RUPTURE THAN STEEL

• ELASTIC BEHAVIOUR WITHOUT YIELDING

• RELATIVELY COSTLY


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• REIFORCEMENT CORROSION

• STRUCTURALE CHANGES, NEW SERVICE DEMANDS,

MODIFIED CODES

• INCREASE OF THE SAFETY LEVELS

• REDUCING THE EXECUTION DURATION

• DESIGN OR EXECUTION FAULTS

STRANGTHENING WITH COMPOSITES


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- WET LAYOUT (FABRIC)

- PREPREG SYSTEMS

- PREFABRICATED SYSTEMS

STRENGTHENING SYSTEMS


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PART A – STRUCTURAL REHABILITATION USING FRP

• FLEXURAL STRENGTHENING OF RC

BEAMS USING CFRP LAMELLAS - ANCHORING SOLUTIONS

PhDs. Eng. Dan DIACONU

Prof. Dr. Eng. Stoian VALERIU

PhDs. Eng. Sorin Codruţ FLORUŢ


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= OBJECTIVE =

=> To clarify some aspects regarded to the influence of some specialanchorage and there inf luences to the overal l behaviour of the RC beamssubjected to flexure.


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= TESTED ELEMENTS =

The beams were cast using Class C32/40 concrete.

RB – reference beam reinforced with 3 Ø16 bars (ft,med=781 N/mm2)

RB2 – second reference beam reinforced with 2 Ø16 bars (ft,med=781 N/mm2)

All of the other beams had the same characteristics as beam RB2, thestrengthening systems being design so that these beams reach the capacity of RBreference beam.

R-1S – RC beam strengthened on bottom face with one C-FRP strip 1,2x50 mm

in section, anchored at both ends with steel plates (150x20...160 mm) connected tothe concrete element by bolts (6 for each steel plate,10 mm diameter)

R-CA-1S – RC beam strengthened on bottom face with one C-FRP strip 1,2x50mm in section, anchored on its entire length with steel bolts (10 mm diameter) thatare chemically anchored in the concrete element


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4,20 a

a

415

stirrups Ø 8/ 15

2Ø 8 L=4,152

4,15

1 3Ø16 L=5,45 3

5

3

20

22Ø 8

3Ø161

4

0

stirrups Ø 8/ 15

3

5

3

5

15

1 5

30 30

3

5

L= 1,15

RB - reinforcement distribution

RB - loading scheme

F F

= RB =


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= RB =


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RB -> 3F16

0

20

40

60

80

100

120

140

160

180

200

220

0 25 50 75 100 125

DISPLACEMENT [mm ]

L O A D

[ k N ]

RB

= RB =

The element reaching an ultimate displacement of 121 mm and withstanding a load of 187kN.


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RB - loading scheme

F F

4,20 a

a

41 5

stirrups Ø 8/ 15

2Ø 8 L=4 ,152

4,15

1 2Ø16 L=5,45 3

5

3

20

22Ø 8

2 Ø 1 61

4

0

stirrups Ø 8/ 15

3

5

3

5

15

1 5

30 30

3

5

L= 1,15

RB2 - reinforcement distribution

= RB2 =


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= RB2 =


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0

20

40

60

80

100

120

140

160

180

200

220

0 25 50 75 100 125

DISPLACEMENT [mm]

L O A D

[ k N ] RB2

RB

= RB2 =

The element reaching an ultimate displacement of almost 100 mm and withstanding a loadof 126 kN.


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= R-1S =


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= R-1S =

In order to choose the most adequate epoxy resin used for anchoring the bolts into concrete,a series of pull out tests have been carried out using two different types of resins.

Resistant torque [Nm] Failure mode

SI

K

A

1 over 54 tear out of bolt

2 over 54 break of bolt

HI

LT

I




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The steps that need to be carried out for this solution are:

•grinding of concrete surface

•drilling of 12 mm diameter bores for attaching the steel plate to the concrete

•cleaning the dust and all other residues by vacuuming and using compressed air

•applying of epoxy resin on the concrete surface

•applying of epoxy resin on the lamella

•lay up of the lamella and applying pressure with the roller

•filling of the bores with anchoring resin

•inserting of the bolts into the resin filled bores•applying of epoxy resin onto the steel plates

•lay-up of the steel plates in a proper position so that they fit with the bolts

•tightening the screw by applying a torque of 40 Nm.

= R-1S =


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The failure mode of the element began with the composite debonding between theanchorages, followed by concrete crushing in the compression zone, and finally by the

sliding out of the FRP from the anchorage simultaneous with the failure of the strip.

= R-1S =


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0

20

40

60

80

100

120

140

160

180

200

220

0 25 50 75 100 125

DISPLACEMENT [mm]

L O A D

[ k N ] RB2

R-1S

= R-1S =

The element reaching an ultimate displacement of 87 mm and withstanding a load of 215 kN.


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= R-CA-1S =


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= R-CA-1S =

In order to verify the resistance of the lamella to local pressure on the hole, a series of tension tests have been carried out :

• solely the lamella – for reference

• with steel plate of 2 mm in thickness glued with resin on one face

• with steel plate of 2 mm in thickness glued with resin on one both faces• with GFRP fabrics wrapped around the lamella in a double layer • with GFRP fabrics glued only on one face in four layers (0-90-45-135)


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The steps that need to be carried out for this solution are:

•drilling of 12 mm diameter bores for attaching the steel plate to the concrete

•cleaning the dust and all other residues by vacuuming and using compressed air

•creating 10 mm holes in the lamella

•positioning the lamella on the RC beam

•filling of the bores with anchoring resin

•fitting the bolts to match the holes in the lamella

•placing the washers

•tightening the screws

= R-CA-1S =


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The element failed by concrete crushing in the compressed zone simultaneously with the

rupture of CFRP lamella at the mid span.


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0

2 0

4 0

6 0

8 0

1 0 0

1 2 0

1 4 0

1 6 0

1 8 0

2 0 0

2 2 0

0 1 5 3 0 4 5 6 0 7 5 9 0 1 0 5 1 2 0 1 3 5

D I S P L A C E M E N T [m m ]

L

O

A

D

[

R B - > 3 F 1 6

R B 2 - > 2 F 1 6

R - C A - 1 S

R B 2

R BR -C A -1 S

[ k N ]

= R-CA-1S =

The element reaching an ultimate displacement of almost 70 mm and withstanding a load of 204 kN.


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0

20

40

60

80

100

120

140

160

180

200

220

0 15 30 45 60 75 90 105 120 135

DISPLACEMENT [mm]

L O A D

[ k N

RB -> 3F16

RB2 -> 2F16

R-CA-1S

R-1S

RB2

RBR-CA-1S R-1S

= COMPARATIVE LOAD – DISPLACEMENT DIAGRAM =


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The two beams strengthened by the above mentioned methods have resisted to loadshigher than the designed one - RB (187 kN).

The ultimate load capacity for element R-1S was higher with 15% than that of RBbeam, but ultimate reached displacement was 28% lower than in the case of RBelement.

The ultimate load capacity for element R-CA-1S was higher with 9% than that of RBbeam, but ultimate reached displacement was 30% lower than in the case of RBelement.

In terms of structural efficiency the first solution is slightly superior, but in terms of easiness of application it is inferior to the second solution.

The second solution (R-CA-1S) limits the use of epoxy resin only to anchoring the

bolts into the concrete beam, significantly reducing the exposure to toxic environmenteffects that it creates while conducting the strengthening procedure.

The execution and curing time it is lower for the second solution in comparison withfirst one (one day for R-CA-1S instead of one week for R-1S).

As it can be seen in the comparative load-displacement diagram, the strengthenedelements presented a slightly higher initial stiffness than the reference beams, but were

characterized by a poorer ductility.

= CONCLUSIONS =


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II. RC BEAMS STRENGTHENED WITH FRPS DIMENSIONING

CROSS SECTION: 20 x 40 CM

SPAN: 400 CM

REFERENCE BEAM 1 (RB): 316

REFERENCE BEAM 2 (RB2): 216

RETROFITTED SPECIMENS: 216

FOR STRENGTHENING DIFFERENT FRP COMPOSITES

SYSTEMS WERE USED, WHICH WERE DESIGNED TO REACH AN

APPROPRIATE LOAD BEARING CAPACITY AS THE FIRST

REFERENCE BEAM (RB).


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II. RC BEAMS STRENGTHENED WITH FRPS TEST SET-UP

400

130 140 130

stirrups Ø8/15 2Ø8

2Ø16

20

4 0


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II. RC BEAMS STRENGTHENED WITH FRPS TEST RESULTS

R-2W strengthened with 2 layer of 18cm wide unidirectional carbon FPR fabric

in the bottom part, without any anchor system.

The failure of the element was through debonding of the FRP.

0

2040

60

80

100

120

140

160

180

200

220

0 25 50 75 100 125

L O A D

[ k N ]

DEFLECTION [mm]

RB2

RB

R-2W


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RL-2W-A strengthened with 2 layer of 9cm wide unidirectional carbon FPR fabric

applied in the lateral part of the both side, anchored with three spikes/end/side.

The failure of the element was debonding inside the FRP.

0

2040

60

80

100

120

140

160

180

200

220

0 25 50 75 100 125

L O A D

[ k N ]

DEFLECTION [mm]

RB2

RB

RL-2W-A


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R-1S strengthened with 1 layer of 5cm wide carbon FPR strip applied in the

bottom part and anchored at the ends with steel plates.

the failure began with the composite debonding between the

anchorages, followed by concrete crushing in the compression zone, and finally by

the sliding out of the FRP from the anchorage simultaneous with the failure of the

strip.

0

20

40

60

80

100

120

140

160

180

200

220

0 25 50 75 100 125

L O A D

[ k N ]

DEFLECTION [mm]

RB2

RB

R-1S


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R-2NSMS strengthened with two 20mm wide carbon FPR strip, in the bottom

part of the beam, applied in cut grooves (NSM technique).

The failure began with the composite debonding in the grooves,

followed by concrete crushing in the compression zone, and finally by the tensile

failure of the FRP strip in the middle region of the beam.

0

20

40

60

80

100

120

140

160

180

200

220

0 25 50 75 100 125

L O A D

[ k N ]

DEFLECTION [mm]

RB2

RBR-2NSMS


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II. RC BEAMS STRENGTHENED WITH FRPS CONCLUSIONS

BASED ON THE PERFORMED EXPERIMENT, RESPECTIVELY ONTHE BEHAVIOUR OF THE TESTED SPECIMENS, THE FAVOURABLE

EFFECTS OF MECHANICAL AS WELL AS CHEMICAL ANCHORAGE

WERE EXPERIMENTALLY DEMONSTRATED, BOTH FOR BOTTOM ANDLATERALLY APPLIED COMPOSITES.

THE MOST EFFECTIVE STRENGTHENING SOLUTION FOR THE

INCREASING OF THE FLEXURAL CAPACITY OF REINFORCED

CONCRETE BEAM PROVED TO BE THE NSM TECHNIQUE


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Ductility Increasing for Concrete Columns:

Experimental Results

• Authors: C. Al. Dăescu,

V. Stoian, T. Nagy-György, D. Dan, I. Demeter

•


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- Strengthening of the RC columns

- Superposition of the two methods of strengthening

(bending and confinement)

- Study on the ductility of the strengthened specimens.


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Testing program – 2nd series:

-BM – Bars of Metal

-AF – Anchored into Foundation

-GW – Glass Wrap

-BC – Base Confinement

-CSS - Carbon Sheet Strand

Element Cons olidation system Test type

C5M Un-strengthened reference specimen from the 2nd casting monotonic

C5C Un-strengthened reference specimen from the 2nd casting cyclic

C6M – GW – BC Base confinement using glass fibre fabric monotonic

C6C – GW – BC Base confinement using glass fibre fabric cyclic

C7M – BM + GW Strengthening for bending using metallic bars anchored into the foundation(2 bars on one side) and strengthening by base confinement using glass fiber fabric.

monotonic

C7C – BM + GW Strengthening for bending using metallic bars anchored into the foundation(2 bars on two sides) and strengthening by base confinement using glass fiber fabric.

cyclic

C8M – CSS – AF Strengthening for bending using carbon sheet strands anchored into the foundation (2 strandson one side)

monotonic

C8C – CSS – AF Strengthening for bending using carbon sheet strands anchored into the foundation (2 strandson two sides)

cyclic

C9M – CSS + GW Strengthening for bending using carbon sheet strands anchored into the foundation (2 strandson one side) and strengthening by base confinement using glass fiber fabric.

monotonic

C9C – CSS + GW Strengthening for bending using carbon sheet strands anchored into the foundation (2 strandson two sides) and strengthening by base confinement using glass fiber fabric.

cyclic


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Abaqus initial model in monotonic loading

Magnitude of principal stresses Direction of principal stresses


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Layout of the testing frame. No axial force applied.

Confinement

CFRP wrap

Steel rods

for bending

HH

E E M d M t C


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Reinforcing Layout of the Specimens

1 8 5

1

3 Ø 1 2

P C 5 2

L

= 2 . 4 0 [ m ]

20

35

1

3 Ø 1 2

P C 5 2

L

= 2 . 4 0 [ m ]

1 8 5

20

35

Column

Reinforcement

Layout

9 Etr.Ø8/10/20

OB37 L = 0.95[m]

1 4

1 4

2 0

2 0

2 0

2 0

2 0

2 0

3 7 . 5

2 . 5

2

20

20

20

20

1 1

1

2

2

23 3

120

3 4Ø16 PC52 L = 1.90[m]

3 5

3 5

120

4 4Ø12 PC52 L = 1.40[m] 1 0

1 0

120

5 4Ø16 PC52 L = 1.60[m]

2 0

2 0

120

6 4Ø12 PC52 L = 1.60[m]

2 0 2

0

22 Etr.Ø10/5/10

OB37 L = 1.25[m]7

35 35

20

20

20

20

1515

22 Etr.Ø8/5/10

OB37 L = 0.85[m]8

Section 1-1

2 5

25

Foundation

Reinforcement

Layout

Section 3-3

Section 2-2

2 5

1.25

4 0

25

E E M d M t C


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Reference specimen [C1]Monotonic loading, with axial force

C1 - Force Displacement Diagram

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 15 30 45 60 75

Displacement [m m]

F o r c e [ d a N ]

D1 - Top displacement

D2 - Midspan displacement



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Reference specimen [C1M]

Monotonic testing

C1M - Force Displaceme nt Diagram

0

500

1000

1500

2000

2500

3000

3500

4000

0 10 20 30 40 50 60 70 80 90 100

Displacement [mm]

F o

r c e [ N ]



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Reference specimen [C1C]

Cyclic testing

C1C - Envelop e Curve

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-100 -75 -50 -25 0 25 50 75 100

Displacement [m m]

F o r c e [ N ]



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Specimen strengthened by a carbon fiber wrap base confinement

[C1C-CW-BC] Cyclic testing

C1C-CW-BC Enve lope Curve

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

-125 -100 -75 -50 -25 0 25 50 75 100 125

Displacement [mm]



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Specimen strengthened using metallic rods anchored into the

foundation. [C3M-BM-AF] Monotonic testing

C3M-BM-AF - Force Displace ment Digram

0

1000

2000

3000

4000

0 25 50 75 100

Displacement [mm ]

F o r c e

[ N

]



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Specimen strengthened using metallic rods anchored into the

foundation and a carbon fiber wrap base confinement

[C4M-BM+CW] Monotonic testing

C4M-BM+CW - Force Displacement Diagram

0

1000

2000

3000

4000

5000

6000

0 25 50 75 100 125 150

Displacement [mm]

F

o

r c e

[ d

a N

]



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Specimen strengthened using metallic rods anchored into thefoundation and a carbon fiber wrap base confinement

[C4C-BM+CW] Cyclic testing

C4C-BM+CW Envelope Curve

-6000

-4000

-2000

0

2000

4000

6000

-100 -75 -50 -25 0 25 50 75 100

Displacement [mm]

F

o

r c e

[ d

a

N

]



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p




Superposition of the individual monotonic tests

Superposit ion of the Monotonic Tests

0

1000

2000

3000

4000

5000

6000

0 25 50 75 100 125 150

Displacemen t [mm]

F o r c e

[ d a N ]

C1M

C3M-BM-AF

C4M-BM+CW



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Superposition of the individual cyclic tests

Superpos i t ion of th e cyc l ic tes ts

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

-125 -100 -75 -50 -25 0 25 50 75 100 125

Displacement [mm]

F

o r c e [ N ]

C1C - left

C1C - right

C1C-BM+CW - lef t

C1C-BM+CW - r ight

C1C-CW-BC - left

C1C-CW-BC - right



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Conclusions

Element Ultimate horizontal

load

[kN]

Difference in the

ultimate horizontal

load [%]

Displacement ductility

factor

μΔ

C1M 35.00 - 3.64C3M-BM-AF 38.30 +9,4% 3.95

C4M-BM+CW 52.00 +48% 6.39

C1C 32.15 - 3.08 … 3.11

C1C-CW-BC 32.50 +1% 3.89 … 5.49

C4C-BM+CW 45.70 +42% 4.50 … 6.39



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• BY

• Ta m ás N AGY- GYÖRGY , P hD , L e c t u r e r Cosmin DĂESCU , Ph D S t u d e n t

• V a l er i u STO I AN , P hD , P r o f e s s o r D a n D I A CONU , P h D S t u d e n t

• D a n i e l D AN , P hD , A s s o c . P r o f . I s t ván DEMETER , Ph D S t u d e n t

•

RCBEAMS STRENGTHENED WITH FRP SYSTEMS –

RESULTS IN DAPPED-ENDS AND

INCREASE OF FLEXURAL CAPACITY



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I. DAPPED BEAM ENDS STRENGTHENED WITH FRPS DIMENSIONING

PRELIMINARY DIMENSIONING AND DETAILING ACCORDING TO THE

ROMANIAN CODES AND VERIFIED WITH EC2, ACI318, PCI IN ORDER TOOBTAIN THE BEARING CAPACITY OF 800 KN

BEAM’S HEIGHT 150 CMDAPPED ZONE 80/80 CMELEMENT WIDTH 66 CM



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INTRODUCTION• Main objectives of the study

- the behaviour of dapped beam ends strengthened with FRP

composites in various layouts

- the effectiveness of the systems used

• Procedure

1. Theoretical investigation

- simplified design (codes)

- numerical analysis

- strut-and-tie

2. Experimental investigations on full scale beam ends


R S R C R R O S G C R


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RESEARCH SIGNIFICANCE

– For dapped beam end there were identified five potential failure

modes (PCI):

(1) flexure (cantilever bending) and axial tension in the extended end,

(2) direct shear at the junction between the dapped and undapped zone ofthe member

(3) diagonal tension on the re-entrant corner

(4) diagonal tension in the extended end

(5) diagonal tension in undapped zone


PART A STRUCTURAL REHABILITATION USING CFRP


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New strengthening techniques

- development of new strengthening solutions for this type of elements, with deficient load bearing capacity, caused by design errors,

structural or codes modifications, increasing loads or structural damage

- the special advantages offered by the composites in structural

retrofitting, compared with traditional solutions currently used

• Previous researches in CFRP strengthening of dapped beam end

Huang, Nanni & a., 2000

Gold, 2001Tan, 2001

Elgwady, 2002




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• The present research program has been performed in the followingsteps:

- predimensioning and detailing the element,

- numerical analysis with finite element

- strut-and-tie method

- experimental testing on four dapped beam ends strengthened with

FRP composites

- interpreting the results and preparing the conclusions




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DIMENSIONING AND DETAILING

• Preliminary dimensioning and detailing of the studied dapped

beam end were made according to the Romanian codes and

verified with those from EC2, ACI318 and PCI Design Handbook,in order to attain the bearing capacity of 80 t (800 kN).

- beam height = 150 cm,

- dapped zone = 80/80 cm

- element width = 66 cm.




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ELEMENT DETAILS

2 Ø

1 Ø

1 Ø

66

2 Ø

2 Ø

12 Ø

66

2 Ø

2 Ø

2 Ø

1-1

8 Ø

12 Ø

12

90

2-2

1 Ø

70

1 Ø

80

1

2

51 50

4 Ø

80

12 Ø

1 2 2 Ø

2 Ø

2 Ø




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NUMERICAL ANALYSIS

• In the theoretical models, there were used the characteristic

strengths of the concrete and the steel reinforcement.

- elastic analysis (FEM)

- nonlinear analysis (FEM)

- Strut-and-Tie (STM)




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Elastic Analysis

Direction and distribution of the principal stresses

The load level corresponding to the yielding limit in the horizontal

reinforcement was 115 t.




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Nonlinear Analysis

Yielding in the horizontal reinforcement started at the load level of 90 t.

Crack pattern at different load levels




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Strut-and-TieThe analysis was performed to determine the maximum force at which the

horizontal bars from the dapped-end are starting to yield.

The maximum force at which the most tensioned reinforcement started to

yield was 94 t.




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EXPERIMENTAL TESTS




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Test results• The elements showed a similar behaviour as maximum load and

deflection

• The design value of the serviceability limit state was 80 t.

• The stress level recorded in the reinforcement was comparable for allthe elements;

• The unloading behaviour was similar for all the specimens, very close

to the initial starting point;

• It was noted a good similarity between the crack pattern for all thespecimens, the general aspect being identical;


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CFRP used characteristics

System Components

Tensile

Strength[N/mm2]

Tensile

Modulus[N/mm2]

Strain at

Failure [‰]

1 →

RC1

SikaWrap 230C

Fabric 300 x 0,12 mm4100 231000 17

SikaDur 330 Resin 30 3800 -

2

→RC2,

RC4

Sika CarboDur S1012

Plate 100 x 1,2 mm2800 165000 17

SikaDur 30 Resin 30 12800 -

3 →RC3

SikaWrap 400C HiModNWFabric300x0,191mm 2600 640000 4

SikaDur 300 Resin 45 3500 15




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S UC U O US G C

Test results–rehabilitated specimen (RC1)

• Specimen RC1 had a linear behaviour up to 160 t

- the first fibre rupture at 160 t

- maximum load was 178 t

- yielding until collapse

-failure mechanism: successive breaking of the carbon fibres along

main crack and not due to fibre debonding or delamination +

concrete crushing in the compressed zone at the maximum load

- maximum displacement was 35 mm

- strain in fibres reached the maximum values




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Crack patterns, load-displacement curves and strains in composite (G)

of the C1 and RC1 elements

V

V

2

13

0

20

40

60

80

100

120

140

160

180

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

DISPLACEMENT [mm]

L O A D

[ t ]

C1

RC1

0

20

40

60

80

100

120

140

160

180

0 2 4 6 8 10 12 14 16 18 20 22

STRAIN [‰]

L O A D

[ t ]

G3 - RC1

G4 - RC1

G5 - RC1

G6 - RC1

G4/G6

G 3 / G 5




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Test results–rehabilitated specimen (RC2)

• Specimen C2 was tested up to 80 t.

- the first crack started at a 42°

- at 65 t appear four major cracks

- the maximum displacement was 6 mm

- strain gages in steel 1.87 ‰ (yielding)


- at143 t appear the peeling-off of the horizontal plates

- maximum load at 176 t when also the vertical plates failed through

peeling-off; the failure was brittle

- the maximum strain in steel was 2.59 ‰ at 148 t

- the maximum strain in composite 7 ‰, which correspond to 41 % ofthe composite’s ultimate value.




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Crack patterns, load-displacement curves and strains in steel

reinforcement (S) and composite (G) of the C2 and RC2 elements

V

V

12 3 4

0

20

40

60

80

100

120

140

160

180

200

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36DISPLACEMENT [mm]

L O A D

[ t ]

RC2

C2

0

20

40

60

80

100

120

140

160

180

0 1 2 3 4 5 6 7 8

STRAIN [‰]

L O A D

[ t ]

S1 - C2

S1 - RC2

G3 - RC2

G4 - RC2

G5 - RC2

G

4 / G 5

G 3

S1


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Test results –rehabilitated specimen (RC3)

• Specimen C3 was tested up to 80 t.

- the first crack started at a 45

- strain in the steel reinforcement 1.95 ‰


- aspect is very close to the one of RC1 specimen

- the maximum load and remanent displacement were identical with

the one from RC1

- the failure was brittle, produced by successive breaking of thecarbon fibres along the main crack


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Test results – rehabilitated specimen (RC4)

• Specimen C4 first crack at 46°

- after 80t four new major cracks developed

- strain in steel 1.44 ‰


-at 119 t a crack developed around the horizontal plates.

- the element failed at 169 t through debonding of vertical plates with

an immediate peeling-off of the horizontal plates; the failure was

brittle

- strain in steel 3.78 ‰ at 153 t

- strain in composite reached 6.72 ‰, which corresponded to 40 %

of the composite’s ultimate value.


S t i bl C t ti d N t l



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1

2

43

0

20

40

60

80

100

120

140

160

180

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

DISPLACEMENT [mm ]

L O A D

[ t ]

C4

RC4

0

20

40

60

80

100

120

140

160

180

0 1 2 3 4 5 6 7 8

STRAIN [‰]

L O A D

[ t ]

S1 - C3

S1 - RC3

G3 - RC3

G4 - RC3

G5 - RC3

G4/G5

G 3

S 2S1

Crack patterns, load-displacement curves and strains in steel

reinforcement (S) and composite (G) of the C4 and RC4 elements


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• The used theoretical models approximate with sufficient accuracy theelements’ behaviour

• The FRP systems used increase the service load

(compared with the reference strain in steel reinforcement at 80t)

• The maximum load bearing capacity of the elements increased

Specimen + ΔSL (%) + ΔUL (%) Δmax(mm)

RC1 - 11 34

RC2 45 10 18

RC3 25 0 27

RC4 40 6 19





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• Elements strengthened with fabrics failed more ductile compared

with those retrofitted with plates

• Strengthened elements exhibit a delay in cracking

• The failure occurred by fibre rupture through principal diagonal crack

in case of fabric used, and by debonding of the horizontal or inclined

plates

• Attention is to be paid for anchorage length in the case of plates





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• BY

• Tamás NAGY-GYÖRGY, Ph.D., Ass. Prof., “POLITEHNICA” UNIVERSITY OFTIMISOARA

• Valeriu STOIAN, Ph.D., Professor, “POLITEHNICA” UNIVERSITY OF TIMISOARA

• Janos GERGELY, Ph.D., Assoc. Prof., UNC CHARLOTTE, USA

• Daniel DAN, Ph.D., Lecturer, “POLITEHNICA” UNIVERSITY OF TIMISOARA

High Performance MaterialsUsed in RetrofittingStructural Masonry Walls





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STUDY THE BEHAVIOUR OF THE UNREINFORCED CLAY BRICK

MASONRY WALLS SUBJECTED TO IN-PLAN SHEAR LOADS

STRENGTHENED WITH FRP COMPOSITES ON ONE SIDE

Field of applications:

- SEISMIC RETROFIT OF STRUCTURAL MASONRY WALLS

- IMPROVE THE SHEAR CAPACITY OF THE MASONRY BUILDING

BEFORE EARTHQUAKE

- RESTORE THE SHEAR CAPACITY OF THE WALLS

OBJECTIVES





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PERFORMING AN ANALYTICAL STUDY

- conceive a device in which the load system creates a pure in-plane shear

of the wall, without much influence from the bending moment

- FEA of the walls, modifying: d/h, f m , Em , V

TESTING, RETROFITTING AND RETESTING OF 5 WALLS

RESEARCH ACTIVITY





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Susta ab e Co st uct o s u de atu a


strenght and stiffness

Masonry Wall

Clay Brick

Frame with very high

H H

V

THEORETICAL MODEL

BIOGRAF

FINITE ELEMENT ANALYSIS


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SPECIMENS TEST SET-UP

• Wall dimension : 150x150 cm• Solid clay bricks units• R.C. contour beam: 50x150x25 cm

• R.C. base: 50x150x25 cm

• Mortar strength > M10 (N/mm2

)





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WALLS RETROFITTED WITH SWM

- SEEMS TO BE APROMISING SOLUTION

- WAS STUDIED THECONTRIBUTION OF THIS TECHNIQUE

THE UM SPECIMEN WAS STRENGTHENED BEFORE TESTING WITH SWM

STAINLESS STEEL BIDIRECTIONAL FABRIC (WIRE MESH) WITH 0.4 mm DIAMETER AND 1.0 mm SPACING, APPLIED WITH AN EPOXY BASED MORTAR.

STRENGTHENING PROCEDURE SIMILAR AS THE USED FOR FRP SYSTEMS





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TEST RESULTS

efrp=0.50%

Differences in capacity : - 23%

Difference in displacement : + 131%

0

20

40

60

80

100

120

140

160

180

200

0 2 4 6 8 10 12 14 16 18 20

HORIZONTAL DISPLACEMENT [mm ]

H O R I Z O N T A

L L O A D

H

[ k N ]

UM1L

UM1R

RM1LRM1R

FAILURE→ EXTENSIVE OPENING OF THE EXISTING CRACKFOLLOWED BY COMPOSITE DEBONDING AT THE CRACKS





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TEST RESULTS

0

50

100

150

200

250

300

350

400

0 2 4 6 8 10 12 14 16 18 20

HORIZONTAL DISPLACEMENT [mm]

H O R I Z O N T A

L L O A D

H

[ k N ]

UM2L

UM2R

RM3LRM3R

efrp=0.15%

Differences in capacity : + 23%

Difference in displacement :

+101%FAILURE→ DEVELOPMENT OF A NEW CRACK AND THROUGH ITSEXTENSIVE OPENING→ THE COMPOSITE WAS DEBONDED JUST IN THE CRACKZONE


Sustainable Constructions under NaturalH d d C t t hi E t



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TEST RESULTS

0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20

HORIZONTAL DISPLACEMENT [mm ]

H O R I Z O N T A

L L O A D

H

[ k N ]

UM3L

UM3R

RM4LRM4R

efrp=0.12%

Differences in capacity : - 16%


+239%FAILURE→ EXTENSIVE OPENING OF THE EXISTING CRACKFOLLOWED BY COMPOSITE DEBONDING JUST IN THECRACK ZONE


Sustainable Constructions under NaturalH d d C t t hi E t



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TEST RESULTS

0

50

100

150

200

250

300

350

0 4 8 12 16 20 24 28 32 36 40


H O R I Z O N T A

L L O A D

H

[ k N ]

UM4L

UM4R

RM5LRM5R



+138%

efrp=1.78%

FAILURE→ EXTENSIVE OPENING OF THE EXISTING CRACKFOLLOWED BY COMPOSITE DEBONDING AT THE CRACKS





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TEST RESULTS



+475%

efrp=0.18%

0

50

100

150

200

250

300

0 2 4 6 8 10 12 14 16 18 20


H O R I Z O N T A L L O A D

[ k N ]

UM5L

UM5R

RM6LRM6R

FAILURE→ FORMING OF MANY NEW CRACKS AND THROUGH THEEXTENSIVE OPENING OF THE EXISTING ONE→ THE COMPOSITE DEBONDED ON LARGE AREAS, NEARTHE CRACK ZONE






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CONCLUSIONS

- The correction and injection mortars had an important role in restoring theload bearing capacity

- A considerable capacity increase was observed for the precracked shear

walls retrofitted with FRP composites

(practically, the load bearing capacity of the cracked walls was negligible)

- The failure of the retrofitted walls was caused by extensive crackingfollowed by FRP debonding and not due to tensile or shear failure of the

FRP (vertical applied composites debonded just in the vicinity of the major

crack, while those applied horizontally debonded in large areas)

- The maximum horizontal displacements increased at least twicecompared with the displacements of the reference specimens that

demonstrated the increase of the ductility

- The most advantageous system glass fabric applied dry application

process





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APPLICATION OF THE RESULTS

• In 2002, after an earthquake, two residential buildings with masonrystructure, built in 60’, situated in town Moldova Nouă, Romania, weredamaged

(courtesy of Sika Romania)






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ON-GOING PROJECTFP6 - PROHITECHEARTHQUAKE PROTECTION OF HISTORICAL BUILDINGS BY REVERSIBLE MIXED TECHNOLOGIES

Retrofitting masonry walls with Steel Wire Mesh (SWM)

SWM: - bidirectional

- application with epoxy resin (similar with FRP)a) zinc coated steel wires Ru ≈ 515 N/mm

2

b) stainless steel Ru ≈ 700 N/mm2






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SIMPLIFIED MODELS

FOR SHEAR RETROFIT OF

MASONRY WALLS

USING FRP (Glass, Carbon, Steel) AND

STEEL SHEATHED TECHNOLOGY

Dan DUBINA, Ph.D., Professor, “POLITEHNICA” UNIVERSITY OF TIMISOARAValeriu STOIAN, Ph.D., Professor, “POLITEHNICA” UNIVERSITY OF TIMISOARA

Tamás NAGY-GYÖRGY, Ph.D., Ass. Prof., “POLITEHNICA” UNIVERSITY OF TIMISOARADaniel DAN, Ph.D., Lecturer, “POLITEHNICA” UNIVERSITY OF TIMISOARACosmin DAESCU, Ph.D.Stud. “POLITEHNICA” UNIVERSITY OF TIMISOARADan DIACONU, Ph.D.,Stud.,”POLITEHNICA” UNIVERSITY OF TIMISOARACodrut FLORUT, Ph.D.,Stud. ”POLITEHNICA” UNIVERSITY OF TIMISOARA Adrian DOGARIU, Ph.D.,Stud.”POLITEHNICA”UNIVERSITY NOF TIMISOARA Aurel STRATAN, Ph.D.,Lecturesr “POLITEHNICA”UNIVERSITY OF TIMISOARASorin BORDEA, Ph.D.,Student, “POLITEHNICA” UNIVERSITY OF TIMISOARA






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p

PURPOSE- establish a simplified design formula

PROCEDURE

- study the behavior of the structural elements →test

- push over test of experimental specimens- establish the collapse mechanism

- propose the design formula

- calibrate the parameters in the design formula for the

retrofitted masonry using:- experimental tests

- numerical analysis






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p

MAIN CONCLUSION FROM TESTS:

- retrofitted masonry: composite element

- behavior: intense cracking process of the

composite system- first phase: formation of smeared crack

- second phase: develop a general diagonal crack

- third phase: damage of the retrofitting material or

system

- collapse: general diagonal crack when thecomposite system stops functioning






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IMPORTANT NOTICE:

- full displacement compatibility between the

retrofitting material or system and the masonry up to

collapse

- different damage process of the retrofitting system:

debonding of the GFRP or CFRP

yielding of the SFRP

plastic bearing of Steel Sheet accompanied by

vanishing the composite character (equivalent to

debonding)






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S M

E A R E D C

R A C K S





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D I A G O N A L C R A C K





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D

E B O N D I N G G F R P





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D E

B O N D I N G

C F R P






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Y I E L D I N G

S F R P






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P L A S T I C B E

A R I N G


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PARAMETERS TO BE EVALUATED

f rm , φ , c






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CALCULATION EXAMPLE

f rm= 0.5 N/mm2

t = 250 mm

l = 2151 mm

σo = 0.5 N/mm2

c = 0.8,

Φ = 1.0

Q = 360 kN





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E X P E

R I M E N T A L R E Z U L T S






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CONCLUSIONS:-THE PRPOSED MODEL SEEMS TO BE

SUITABLE FOR THE PRACTICAL DESIGN OF

RETROFITT MASONRY WALLS

-THE NUMERICAL ANALYSIS IS PERFORMED

USING BIOGRAF SOFTWARE

-THE PROPOSED DESIGN FORMULA AND THE

SOFTWARE CAN BE APLLIED FOR R.C.STRUCTURAL WALLS






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Daniel Dan

Alexandru Fabian

Valeriu Stoian

Tamas Nagy-György

Politehnica University of Timisoara

Introduction

COMPOSITE STEEL-CONCRETE SHEAR WALLS ARE REINFORCED CONCRETE WALLS

OBTAINED BY REPLACING THE VERTICAL REINFORCEMENTS FROM THE EDGES BYSTEEL ENCASED PROFILES

Examples of the solution in practice

Experimental specimens


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L10 – B.2 – Mechanical properties of ca

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