Professor Andreas J Kappos

Founding Director of the Research

Centre for Civil Engineering

Structures, City, University of London

Faculty Lead Structures,

Department of Civil Infrastructure

and Environmental Engineering,

Khalifa University, Abu Dhabi

Seismic performance of

retrofitted bridges

KN LECTURE

Acknowledgement

• The contribution of Dr S. Stefanidou, former PhD student at

the Aristotle University of Thessaloniki, is gratefully

acknowledged

Are bridges vulnerable to earthquakes?

Chile 2010 earthquake,

Collapse of Romero Bridge

(Kawashima et al., 2011)

Kobe 1995 earthquake:

Collapse of Hanshin

expressway

Causes of bridge failures

Causes of Failure

Failure Types

Total/causeTotalCollapse

PartialCollapse

Distress (member failure)

Design Error 38% (8) 52% (11) 10% (2) 21 (3%)

Lack of Maintenance

67% (2) 33% (1) 0% (0) 3 (0.4%)

Deficiency in Construction

32% (10) 65% (20) 3% (1) 31 (5%)

Material Defect 23% (3) 46% (6) 31% (4) 13 (2%)

Earthquake 38% (6) 63% (10) 0% (0) 16 (2.5%)

Scour 50% (61) 50% (60) 0% (0) 121 (19%)

Flood 75% (83) 25% (27) 0% (0) 110 (17%)

Collision 39% (44) 60% (68) 1% (1) 113 (18%)

Environmental Degradation

29% (12) 69% (29) 2% (1) 42 (7%)

Overload 76% (71) 24% (23) 0% (0) 94 (15%)

Fire 50% (12) 50% (12) 0% (0) 24 (4%)

Wind 78% (35) 22% (10) 0% (0) 45 (7%)

US data from: MCEER-13-0008

Damage modes of bridges under earthquake

source: MCEER-13-0009

modes

- Bridges : The most vulnerable component of the transportation system

- Direct losses : Can be high (e.g. $1.8 billion in Loma Prieta 1989)

Need for…

Damage Control

Lap spliced zone retrofit with CFRP sheet jacket

retrofit with steel plates

steel plates connected by equal leg angle steel profiles

Usual methods of pier retrofitting

repair of damage should precede the application of the jacket/plates

Fakharifar et al. (2015)

Schematic of different repair techniques: (a) CFRP jacket, (b) conventional steel or R/C jacket, and (c) hybrid jacket.

Hollow piers before and after shear retrofitting with CFRP strips

Delgado, P. and Kappos, A.J., “Strengthening of RC Bridges”, in Strengthening and Retrofitting of Existing Structures, Spinger, 2018

Shear strengtheningof hollow piers

shear strength:

sjpscd VVVVV

contribution of CFRP jacket:

cot hfs

AV j

j

sj

first CFRP strip rupture at 3.0% drift

Experimental and analytical results

13

Fragility Analysis of Retrofitted Bridge Piers

14

2 2 2

tot C D LS

1 1

max[P(F)] ( ) 1 [1 ( )]n

i system ii i

P F P F

2

, , ( )1 ln

f tot g m g LS iP A A

All possible combinations

Ratio As Built / Retrofitted

My , φy (EIeff) & local EDP(thresholds): φ1, φ2, φ3, φ4

AnySection(Papanikolaou, 2012)

12

34

5

0

2

4

60.8

1

1.2

1.4

1.6

1.8

w,j

/w,c

y,j

/y,c

- l,j

/l,c

- w,j

/w,c

l,j

/l,c

y,j/

y,c

12

34

5

0

2

4

6

1.4

1.6

1.8

2

w,j

/w,c

u,j

/u,c

- l,j

/l,c

- w,j

/w,c

l,j

/l,c

u

,j/

u,c

15

Jacketed Piers

Core confinement?

(𝛿1~4,𝑅𝐶𝑗𝑎𝑐𝑘) = [ 𝛽0+ 𝛽1𝐷𝑗𝑎𝑐𝑘

𝐷𝑐𝑜𝑟𝑒+

𝛽2𝜌𝑙,𝑗𝑎𝑐𝑘

𝜌𝑙,𝑐𝑜𝑟𝑒+ 𝛽3

𝜌𝑤,𝑗𝑎𝑐𝑘

𝜌𝑤,𝑐𝑜𝑟𝑒+ 𝛽4

𝑓𝑐,𝑗𝑎𝑐𝑘

𝑓𝑐,𝑐𝑜𝑟𝑒+

𝛽6𝑓𝑦,𝑗𝑎𝑐𝑘

𝑓𝑦,𝑐𝑜𝑟𝑒] × (𝛿1~4,𝐴𝑠𝐵𝑢𝑖𝑙𝑡)

Regression Analysis

(robust fit, least squares for linear equality constraints)

Empirical Relationships

Component – specific thresholds

16

H=5~20 m (Ls=2.5~10 m) Global EDP(thresholds): δ1, δ2, δ3, δ4

Uncertainty (LHS)

17

Core R/C Jacket

FRPJacket

FRPJacket

R/C Jacket

Core

NRHA (Nonlinear Response History Analysis x & y)

Incremental Dynamic Analysis (IDA - 0.1g1g+)

LHS Sampling 0.1 1g, 1000 analyses)

Displacement demand at control point

Uncertainty in demand and total uncertainty (βtot)

βtot = (βc2 + βd|IM

2 + βLS2 )1/2

, ,1~41

1~4

1ln( )

g ma

1 1

max[P(F)] ( ) 1 [1 ( )]n

i system ii i

P F P F

,

2, ( )

1ln

g m

f

g LS itot

AP

A

Component Fragility Curve

System Fragility Curves

18

Total loss scenarios for the road network of Western Macedonia, Greece

Piers

,2.2

cu c syv

Bridge retrofit : Equivalent effectiveness

21

22

, ,0.004 (1.4 )

cu c s ym su cm cf f

1

2Ecc

Ecju cc

cu cc

c cc

E

E E

2.50.004

j j ju

cu

cc

f

f

23

R/C Jacket: Effect of ρl & dj

Increase ρl & dj Fragility reduction

Variation of ρl of jacket Slightly less effective than thickness variation (dj)

R/C - FRP Jacket

LS2-LS3 :

R/C Jacket more effective than FRP

LS4

FRP Jacket more effective than RC

CFRP More effective than GFRP

24

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Websites:

@ Khalifa University @City University Personal

Sheikh Zayed Bridge, Abu Dhabi