bruno briseghella repair and retrofitting of rc bridge...

Repair and Retrofitting of RC Bridge Piers toImprove Plastic Dissipation and Shear Strength

Bruno Briseghella ([email protected])Professor and Dean, College of Civil Engineering, Fuzhou University (China)

Camillo Nuti ([email protected])Professor, Department of Architecture, Roma Tre University (Italy)

Visiting Professor, College of Civil Engineering, Fuzhou University (China)Marcello Tarantino ([email protected])

Professor, Department of Engineering, University of Modena and Reggio Emilia (Italy)

The Seventh Kwang-Hua Forum on Innovations and Implementations in Earthquake Engineering ResearchShanghai, December 9-11th 2016

College of Civil Engineering Fuzhou University

Department of ArchitectureRoma Tre University

Department of Engineering “Enzo Ferrari”

Bergami A., Carnevale L., Fiorentino G., Furgani L., Lanzoni L., Lavorato D., Nuti

C., Santini S., Sguerri L., Xsu L., Tarantino M., Zhihao Z., Vanzi I., Biondi S.

Briseghella B., Marano, B., Huang Y., Huang F., He L., Liu T., Mazzarolo E.,

Munoz M., Xue J., Zhou W, Gu Y.

Acknoledgements

Seismic Design and Retrofitting of Structures

Master and PhD students: Angela Falotico, Daniele Napoli, Matteo Pietrobelli, Andrea Sacchetti, Davide Toto, Shangjie Nie, Wu Jiajie, Matteo Giovannini, Hai Bin Ma, Matteo Pellicciari, Tommaso Cuoghi




Fip IndustrialeRoma Tre UniversityInternational Joint Labs

Pt 30Pt 31

Pt 1

Pt 32

Pt 39

Pt 16 Pt 17

500kN Actuator

Load cell A(B)

Reaction beam

Hydraulicjack M1(M2)Column

anchoringsystem

Hinge

Specimen

Verticalframe

Tophinge Horizontal

Load cell

Acknoledgements




National Center for International Research

Acknoledgements




Contents

1. Introduction. Goals and History of the research

2. Phase 1-2. Typical experimental damages after tests on substandard bridges (old code prescriptions). Retrofitting criteria with advanced materials: Carbon and stainless steel, SCC, CFRP

4. Phase 3. Improvement of the retrofitting techniques & application to Chinese bridges

5. Phase 4. Test results of the improved retrofitting:1. New rebar connections2. New concrete UHPRC with steel or polymer fibers

6. Conclusions. Results and future steps




Is it possible to repair and retrofit it?

1. Introduction‐ Goals of the research




‐ Goals of the research A. How to repair quickly RC bridge piers subjected to large damages after strongseismic events.

‐ Use of advanced materials to guarantee: safety, durability, simplicity (quickand error free)

‐ Expected life is increased (better performances)‐ Materials used are: self compacting concrete (with/without fibres), CFRP,stainless steel.

B. Comparison between European and Chinese Codes and MaterialsC. UHPRC – STEEL FIBERS/POLIMER FIBERS – NO STIRRUPS?

7

1. Introduction




1) Italy 1992‐1998: EUROPEAN (EC8) AND ITALIANBRIDGES WITH AND WITHOUT PROPER SEISMICDETAILS RESPECTIVELY

2) Italy 2005‐2011: RAPID REPAIR AND RETROFITTINGOF BRIDGE SEVERELY DAMAGED

3) Italy 2011‐2014 + China 2013‐2014: IMPROVEMENTSOF THE RAPID REPAIR TECHNIQUE and APPLication ONCHINESE PIERS.

TECHNOLOGY/DESIGN/CODE

4) Italy 2014‐2016 + China 2014‐2016 IMPROVEMENTSOF THE RAPID REPAIR TECHNIQUE AND APPLICATIONON CHINESE PIERS (2015 Italy = Roma Tre +Modena)

TECHNOLOGY/DESIGN/MATERIALS

Calibration and check ofEC8; check old italian codesubstandards by pseudo‐dynamic tests (PSD)

To evaluate the effectiveness of the new rapid repair technique by pseudo‐dynamic test (PSD)

to evaluate the effectiveness of the improved rapid repair (1) technique by cyclic tests

• Continuous deck/single circular piers

to evaluate the effectiveness of the improved rapid repair (2)(3) technique by cyclic tests

1. Introduction‐ History of the research

Phases:




‐ Proposed repair and retrofitting technique The retrofitting consists of: ‐ phase 1) damaged concrete removal; ‐ phase 2) concrete core restoration with resin injections;‐ phase 3) damaged rebars substitution using standard or stainless steel ones; ‐ phase 4) damaged concrete restoration by self‐compacting concrete (SCC);‐ phase 5) shear strengthening by carbon fiber reinforced polymer composites (CFRP)

3. Phase 1‐2




‐ Proposed repair and retrofitting technique The proposed technique intends to:a) Limit the repair intervention to the most damaged part of the pier only and toreuse, as much as possible, the original element reducing the cost;b) To reach the scope of simple and quick repair, the new concrete is poured usingSCC with great mobility also in small spaces congested with reinforcement;c) Confinement and shear resistance are obtained by C-FRP wrapping;d) To increase the durability, the use of new reinforcement in stainless steel(important for piers in contact with water and moist) is proposed and investigated.

3. Phase 1‐2




7m21m

14m 50m

200m A

AB B

RR

BO

rigin

al

ORIGINALRRB

Bar failure?

Original (EC8) Vs repaired and seismic upgraded (RRB) specimen‐ Proposed repair and retrofitting technique. PSD Tests

3. Phase 1‐2




A. Improvement of Rapid Repair and Retrofitting Techniques:problem of connection between the new rebar part and theoriginal anchorages (asymmetric)

B. Retrofitting materials: a) Comparison between italian andchinese carbon and stainless steel, b) SCC Concrete, c) FRP

‐ Improved repair and retrofitting technique4. Phase 3

After concrete cover removal: failure of the connection during tests




- Different types of weldingsAsymmetric side welding (Misalign)

ImprovementSymmetric side welding

‐ Smaller new bars ‐ Butt weld

‐ Symmetric butt welding ‐ Smaller new bars or turned rebar!!!

- Connection system between the new rebar portions and the original anchorages by head welding: Simple to realize in situ No eccentricity between the rebar axes as in case of side welding.

- New rebar properly turned to reduce the original rebar diameter: assure the distribution of the plastic demand along these new rebar

part in plastic hinge only according capacity design rules. Elastic behavior of anchorages

‐ Improved repair and retrofitting technique4. Phase 3




- Similitude criteria between model (1:6) andprototype are in terms of global quantities:flexural and shear strength, confinement effect(De Sortis et al. 1994) C-FRP wrapping with 1/2/3 layers of C-FRP

to increase the shear strength according toChinese capacity design prescriptions(JTG/T B02-01-2008). (100mm spacing of thespiral to assure quick and simple cast ofconcrete)

- Turned rebar at the pier specimen base: length = Lp plastic hinge length (Priestley et al.

1996) or length = 0.5 Lp rebar diameter reduction 3-4 mm, to assure

anchorages section in elastic range only

Pier specimen scaled 1:6 with (P26,P36,P46) and without (P16‐3A, P16‐3B) turned rebar

Chinese pier specimens (P26, P36, P46)with turned rebars: different longitudinalturned rebar configurations

‐ Pier Tests. Specimens4. Phase 3




CYCLIC TESTS ON SPECIMENS P13‐3A (not reduced) AND P26 (reduced)

15

4. Phase 3‐ Phase 3) Pier 2014‐2015 (Fuzhou+ Roma Tre)

BARRE NONTORNITE

P 16‐3A

NO reduced REBAR

BARRE TORNITE

P26

Reduced REBAR

reducedbarsL=250mm

No Turnedbars

Research on: a) Chinese materials Vs European b) new bar substitution methods

Reduced diameter REBARS




H1

V1, V2, V3[B]

VIEW 2

D3 ︵A ︶D3 ︵B ︶

D2 ︵A ︶D2 ︵B ︶

D1 ︵A ︶D1 ︵B ︶

V1, V2, V3[A]

Vertical JackN = 1000 kN

Horizontal Jack H = 500 kN

Anchorages

POTENZIOMETERS15 total

LVDT10 total

Vertical Load

3

4

5

910

2

18

7

VIEW 2

Load DirectionLoad Direction

‐15.33

14.33

‐36.33

30.67

‐40‐30‐20‐100

10203040

Spostamen

to [m

m]

Tolmezzo

Tolmezzo x2

Load Path

STRAIN GAGES: a) CFRP (32 in tot); b) Bar (26 in tot)

‐ Pier Tests. Test Set‐Up and Instrumentations4. Phase 3

vertical constant load 266kN




- C-FRP wrapping excludes the shear failure with maximumexperimental deformation similar to the design one equal to 0.005

- Axial and bending forces produce not uniform confining pressure (itis generally taken uniform in design)

- Turned rebar zone shows abrubt change in FRP deformation

P16-3AP26

‐ Pier Tests. CFRP Results4. Phase 3

Experimental confining pressure P16‐3A (original) e P26 (turned) during Cyclic actions

0

0.5

1

1.5

2W1‐1

W1‐8

W1‐7

W1‐6

W1‐5

W1‐4

W1‐3

W1‐2

fl_FIB ‐ R2 P16‐3Afl_FIB ‐ R1 P16‐3Afl_FIB ‐ R1 P26fl_FIB ‐ R2 P26




dy= 5.81 mm15% of the Max displacement

Strain gages

A

C

B

Actuator

Actuator

0

5

10

15

20

25

‐0.0025 ‐0.002 ‐0.0015 ‐0.001 ‐0.0005 0 0.0005 0.001 0.0015 0.002 0.0025

Posizion

e sulla

barra [m

m]

Deformazione [ε]

Rebar 2 and Rebar 9 0.2dy PUSH

0.4dy PUSH

0.6dy PUSH

0.8dy PUSH

dy PUSH

2dy PUSH

0.2dy PULL

0.4dy PULL

0.6dy PULL

0.8dy PULL

dy PULL

2dy PULL

A

C

B

Beyond Yielding, strain gauges do not workTurned Rebar strains concentrate at point C

P26 Strain gages R2‐R9: Strain at different top displacemets‐ Pier Tests. Rebar Strains Results

4. Phase 3




‐ Design goal obtained: plastic deformation demand concentrateson turned rebar

‐ Damage of the pier is controlled and constrained within thehinge zone according to correct seismic design criteria

TURNED REBAR

‐ Pier Tests. Rebar Strains Results4. Phase 3




1. Base shear – Top Displacement

PD1 (continuous line) PD2 (dashed line).

A. P16-3A without turned rebar B. P26 with turned rebarP26: strength reduction, stable behavior

‐ Pier Tests. Cyclic tests Results

2. Comparison base shear – top displacementsP16‐3A (Original) VS P26 (turned)

4. Phase 3




Goals:

A. Simplify- Casting/bar substitution- Optimize rebar Connection

B. Use new concrete:- Increase durability - to reduce transverse reinforcement- Faster- No prolems due to damage to wrapping

5. Phase 4

‐ Phase 4) Italy: Roma Tre + Modena ; China: Fuzhou




welding in vertical

22

0 10 20 30 40 50 60 70 800

20

40

60

80

100

120

140

160

荷载

(kN

)

位移 (mm)

R7-1 R7-2 R7-3

0 10 20 30 40 50 60 70 800

20

40

60

80

100

120

140

160

荷载

(KN

)

位移 (mm)

R8-1 R8-2 R8-3

0 10 20 30 40 50 60 70 800

20

40

60

80

100

120

140

160

荷载

(KN

)

位移 (mm)

R9-1 R9-2 R9-3

0 10 20 30 40 50 60 70 800

20

40

60

80

100

120

140

160

荷载

(KN

)

位移 (mm)

R10-1 R10-2 R10-3

Weld length=2d Weld length=3d

Weld length=4d Weld length=5d

‐ Rebar Connection5. Phase 4

Number Length ofconnection

Reduced rebars Shear reinforcement Wrapping

Concrete Test Original name

L D PH OPH [N Layers]

1

2d

250 15 Sp φ4/60 Sp φ4/60 Frp 1 SCC complete P16‐1A

2 125 15 Sp φ4/60 Sp φ4/60 Frp 1 SCC P36

3 250 12 Sp φ4/60 Sp φ4/60 Frp 1 SCC P16‐3A

4 250 15 Sp φ4/60 Sp φ4/60 Frp 1 Uhpc P16‐1B

5 250 15 St φ4/60 Sp φ4/60 Frp 1 Uhpc (i) P16B

6 250 15 ‐‐‐‐‐‐ Sp φ4/60 ----- Uhpc( i) P16‐3B

7 250 15 ‐‐‐‐‐‐ Sp φ4/60 ----- Uhpc P16‐2

8 250 15 ‐‐‐‐‐‐ Sp φ4/60 ‐‐‐‐‐ Uhpc P46

Two types oc steel fibers have been adoptedNo stirrups, no wrapping

5. Phase 4

‐ Phase 4) Specimen 2015‐2016 SCC Vs UHPC




The fibers, being a bridge between the cracks, providing a greater shear

resistance, ductility, toughness fracture energy, post-

cracking resistance

%3 %2 %1200

2000

65

20.0

13

f

f

ff

f

f

V GPay ElasticitModulus of

MParengthtensile st

dlD

mmd

mml

5. Phase 4

‐ Steel Fiber




Comparation

SpecimenLongitudinal reinforcement

Turned rebars warpping

L D [N Layers]

P16-1A 14 ɸ18 - - 1

P26 14 ɸ18 250 15 3

R16-1A 14 ɸ18 250 15 1

5. Phase 4




• Is it possible to use UHPC and - No stirrups ?????- No wrapping ????

To assess feasibility:A. OpenSees Model

+B. Lab tests

5. Phase 4





OpenSees SCC OpenSees UHFRC

Fmax 192,063 δmax 30,74 Fmax 218,444 δmax 30,74

Fmin ‐197,29 δmin ‐36,39 Fmin ‐226,623 δmin ‐36,39

Fiber2: Larger force, same displacements

5. Phase 4

‐ OPENSEES. SCC Vs UHPFRC




Er %>

totRd,V CLSRdUHFRCRdc VVV ,,0,

Ok if fiber % = 2% and 3%

5. Phase 4

‐ OPENSEES. UHPFRC: Shear Resistance

ShearFIBRE %

Unit1% 2% 3%

VRd,CLS 49,8 49,8 49,8 [kN]

VRd,UHFRC 137,2 149,4 156,2 [kN]

VRd,tot 187,0 199,2 205,9 [kN]

Vc,0 197 197 197 [kN]




Number Length ofconnection

Reduced rebars Shear reinforcement Wrapping

Concrete Test Original name


1

2d

250 15 Sp φ4/60 Sp φ4/60 Frp 1 SCC complete P16‐1A

2 125 15 Sp φ4/60 Sp φ4/60 Frp 1 SCC P36

3 250 12 Sp φ4/60 Sp φ4/60 Frp 1 SCC P16‐3A

4 250 15 Sp φ4/60 Sp φ4/60 Frp 1 Uhpc P16‐1B

5 250 15 St φ4/60 Sp φ4/60 Frp 1 Uhpc (i) P16B

6 250 15 ‐‐‐‐‐‐ Sp φ4/60 ----- Uhpc( i) P16‐3B

7 250 15 ‐‐‐‐‐‐ Sp φ4/60 ----- Uhpc P16‐2

8 250 15 ‐‐‐‐‐‐ Sp φ4/60 ‐‐‐‐‐ Uhpc P46

Two types of steel fibers have been adoptedNo stirrups, no wrapping

5. Phase 4





Turned rebars Shear reinforcement Wrapping

ConcreteTime of Cast

concreteOriginal name Test


250 15 ‐‐‐ Sp φ4/60 --- UHPC(i) 4.20 P16‐3B 6.16

5. Phase 4

‐ Tests pier R16‐3B. UHPC

-40 -30 -20 -10 0 10 20 30 40-300

-200

-100

0

100

200

300

Displacement (mm)

Fo

rce

(KN

)

R16-3B P16-3B

• No stirrups • No wrapping




THE USE OF ADVANCED MATERIALS ALLOWS TO INCREASE LIFE CYCLE OF CONCRETEPIERS THROUGHOUT QUICK AND SIMPLE INTERVENTION

THE USE OF SEGMENT WITH REDUCED BAR DIAMETER ALLOW THE EFFICIENTSUBSTITUTION OF DAMAGED REBARS AT THE BASE OF CANTILEVER PIERS.

BASE YIELD BENDING MOMENT REDUCES IN A CONTROLLED MANNER. HOWEVER ACHECK OF BAR BEHAVIOR IS ESSENTIAL.

THE REDUCTION OF THE DIAMETER ALLOWS A REAL CONTROL OF THE PLASTIC ZONE,THEREFORE LARGER DUCTILITY COULD BE PERMITTED (LARGER Q VALUES TO REDUCESEISMIC DESIGN ACTION)

NEW DETAILS FOR RETROFITTING ARE BEING IMPLEMENTED

WORK IS IN PROGRESS ON POSSIBLE USE OF UHPC WITH/WITHOUT OUT STIRRUPS ANDWRAPPING

6. Conclusions




thank you! 谢谢 grazie! gracias!

Aknowledgements:• Italian Civil Protection• Chinese Ministry for Science and Technlogy• Kerakoll Italia• Cementi Buzi Spa• All Sino- Italian suppliers for materials

The Seventh Kwang-Hua Forum on Innovations and Implementations in Earthquake Engineering ResearchShanghai, December 9-11th 2016




bruno briseghella repair and retrofitting of rc bridge...

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