Upload
others
View
4
Download
0
Embed Size (px)
Citation preview
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
25
Websites:
@ Khalifa University @City University Personal
Sheikh Zayed Bridge, Abu Dhabi