Post on 19-May-2018
Repair and Retrofitting of RC Bridge Piers toImprove Plastic Dissipation and Shear Strength
Bruno Briseghella (bruno@fzu.edu.cn)Professor and Dean, College of Civil Engineering, Fuzhou University (China)
Camillo Nuti (camillo.nuti@uniroma3.it)Professor, Department of Architecture, Roma Tre University (Italy)
Visiting Professor, College of Civil Engineering, Fuzhou University (China)Marcello Tarantino (angelomarcello.tarantino@unimore.it)
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
National Center for International Research
Acknoledgements
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
Is it possible to repair and retrofit it?
1. Introduction‐ Goals of the research
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
‐ 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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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:
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
‐ 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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
‐ 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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
- 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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
- 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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
- 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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
‐ 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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
• Is it possible to use UHPC and - No stirrups ?????- No wrapping ????
To assess feasibility:A. OpenSees Model
+B. Lab tests
5. Phase 4
‐ Phase 4) Specimen 2015‐2016 SCC Vs UHPC
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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]
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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 of steel fibers have been adoptedNo stirrups, no wrapping
5. Phase 4
‐ Phase 4) Specimen 2015‐2016 SCC Vs UHPC
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
Turned rebars Shear reinforcement Wrapping
ConcreteTime of Cast
concreteOriginal name Test
L D PH OPH [N Layers]
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”
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
College of Civil Engineering Fuzhou University
Department of ArchitectureRoma Tre University
Department of Engineering “Enzo Ferrari”