Download - University of Illinois Contribution
University of Illinois Contribution
Jan. 23, 2009
Amr S. ElnashaiSung Jig KimCurtis Holub
Seismic Simulation and Design of Bridge Columnsunder Combined Actions, and Implications on System Response
Analytical Investigation
Effect of V/H Ratio
16 V/H ratios per earthquake record (5 stations) Axial force variation increases noticeably by up to 600% due to
vertical ground motion The slight increases in shear demand and noteworthy reductions
in shear capacity of up to 30% as V/H ratio increases.
0 0.5 1 1.5 2-30
-20
-10
0
10
V/H Ratio
Eff
ect
of
VG
M (
%)
Shear Demand
LP-COR-L
NO-SCS-LLP-COR-L
NO-SCS-L
Shear Capacity
0 0.5 1 1.5 20
100
200
300
400
500
600
V/H Ratio
Rat
io o
f C
on
trib
uti
on
of
VG
M o
nA
xial
Fo
rce
Var
iati
on
to
Dea
d L
oad
(%
)
LP-COR-L
LP-COR-T
NO-ARL-L
NO-ARL-T
NO-SCS-L
NO-SCS-T
KB-KBU-L
KB-KBU-T
KB-PRI-L
KB-PRI-T
595%
Effect of Time Interval
11 cases of arrival time intervals for each record– Results were compared against the response with coincident horizontal
and vertical peaks. The contribution of vertical ground motion to the axial force
variation tends to be reduced as time interval increases. – The effect was relatively small when compared to the effect of V/H ratio.
Although no clear correlation exists between the shear demand or capacity and the time lag, noticeable changes are noted up to 20%
0 1 2 3 4 5-15
-10
-5
0
5
10
15
20
TimeLag (sec)
Eff
ect
on
th
e S
hea
r C
apac
ity
(%)
LP-COR-L
LP-COR-T
NO-ARL-L
NO-ARL-T
NO-SCS-L
NO-SCS-T
KB-KBU-L
KB-KBU-T
KB-PRI-L
KB-PRI-T
Shear capacity
LP-COR-L
LP-COR-T
NO-ARL-L
NO-ARL-T
NO-SCS-L
NO-SCS-T
KB-KBU-L
KB-KBU-T
KB-PRI-L
KB-PRI-T
LP-COR-L
LP-COR-T
NO-ARL-L
NO-ARL-T
NO-SCS-L
NO-SCS-T
KB-KBU-L
KB-KBU-T
KB-PRI-L
KB-PRI-T
Axial Force Variation
0 1 2 3 4 5-100
-75
-50
-25
0
25
50
TimeLag (sec)
Rat
io o
f A
xial
Fo
rce
Var
iati
on
C
ause
d b
y V
GM
to
Dea
d L
oad
(%
)
LP-COR-L
LP-COR-T
NO-ARL-L
NO-ARL-T
NO-SCS-L
NO-SCS-T
KB-KBU-L
KB-KBU-T
KB-PRI-L
KB-PRI-T
Large Scale Experiments
Prototype and Test Matrix
Prototype: FHWA Bridge #4– Half scale pier (D=610mm, H=3048mm)– Rebar ratios: 2.79% for long.; 0.84 and 0.50% for spiral
Test Matrix– Hybrid Simulation: IPH and IPV
Specimen Input Control Type
IPH Horizontal ground motion
Displacement ControlIPV
Horizontal and vertical ground motions
Prototype and Test Matrix
Prototype: FHWA Bridge #4 Test Matrix
– Hybrid simulations : IPH and IPV
– Cyclic Static Tests: ICT and ICC
• Consideration of the observed axial force levels obtained during the second hybrid simulation
Specimen Input
ICTCyclic lateral displacement with constant axial tension
ICCCyclic lateral displacement with constant axial compression
• Displacement Control for Lateral
and Rotational displacements• Force Control for Axial Forces
Dx
Fy
y
Hybrid Simulation
ComponentEffect of VGM (%)
Peak Variation
Dx (mm) 6.97 4.67
Dy (mm) 25.44 27.48
Rz (rad) -9.72 -5.13
Fx (kN) -12.91 -3.60
Fy (kN) 31.70 98.01
Mz (kN-m) -9.07 -2.37
Ground Motions– Sylmar Converter Station, Northridge
Earthquake (Mw 6.7)– V/H ratio: 1.2 (ah=0.61g and av=0.73g)
No notable change in lateral displacement and moment
Significant effect on axial force variation (increases of up to 100%)– Fluctuation of lateral stiffness – Axial tension force (390 kN)
0 1 2 3 4 5 6 7-50
0
50
100
150
Time (sec)
Dx
(mm
)
IPH
IPV
0 1 2 3 4 5 6 7-1000
-500
0
500
1000
1500
Time (sec)
Mz
(kN
m)
IPH
IPV
0 1 2 3 4 5 6 7-3000
-2000
-1000
0
1000
Time (sec)
Fy
(kN
)
IPH
IPV
-60 -40 -20 0 20 40 60 80 100 120-800
-600
-400
-200
0
200
400
600
800
Dx (mm)
Fx
(kN
)
IPH
IPV
IPH and IPV
IPH IPVBlue: IPH
Red: IPV
Left Front Right
Crack and Strain
Crack Longitudinal strain and curvature – No significant effect Spiral strain
– Significant increase up to 200% when vertical ground motion is included
0 0.002 0.004 0.006 0.008 0.01 0.012 0.0145
10
15
20
25
30
35
40
45
50
55
60
Spiral strain
% o
f P
ier
Hei
gh
t
1st peak
2nd peak3rd peak
4th peak
5th peak
6th peak7th peak
Yield strain
Thin line: IPHThick line: IPV
IPH
IPV
IPH and IPV
Cyclic Tests
Loading Scenario– Positive cyclic lateral displacement with constant axial load– ICT: 222 kN (50 kips), ICC: -1112 kN (250 kips)
ICT: ductile behavior and strength increase by 4% ICC: brittle shear failure and strength degradation by 56%
ICT ICC
-50 0 50 100 150 200 250-500
-250
0
250
500
750
1000
Dx (mm)
Fx
(kN
)
ICT
ICC
56%
ICT and ICC
Conclusions
The hybrid simulations results confirmed that the vertical motion can significantly affect pier behavior
Significant increase (up to 100%) of axial force variation leads to more severe cracking and damage
Spiral strains increased by 200% when vertical ground motion is included
The cyclic tests confirmed that the different axial load level can impact the pier behavior and change the failure mode
Small Scale Experiments
Small Scale Testing Program
Experimental Setup (1/10 Scale)
Small Scale Testing Program
28 specimens 1/10 scale of
ICC and ICT Various lateral
and vertical loading patterns and magnitude
Test Matrix
Pseudo-DynamicMonotonic 1-Sided Cyclic 2-Sided Cyclic GM
High Tension 1 10
Low Tension 2 10 - CABER 3 11 22
Zero 3 12
Low Compression 4 11 - CABER 4 13 23
Moderate Compression 5 14
High Compression 6 15
T-C-C 16
C-T-C 17
C-C-T 18
V/H #2 7 19
V/H #3 8 20
V/H #4 9 21
No Vertical 24
V/H #1 25
V/H #2 26
V/H #3 27
V/H #4 28
StaticLateral LoadingCABER PIER (h/d = 2)
Flexure/Shear Failure
Ve
rtic
al
Lo
ad
ing
Co
nst
an
tP
seud
o-D
ynam
icA
ltern
ate
C
ycle
sH
igh
F
requ
en
cy
Small Scale Testing Program
30% axial compression Cyclic lateral loading
Preliminary Test
-0.2 -0.1 0 0.1 0.2 0.3-1.5
-1
-0.5
0
0.5
1
1.5
Displacement, inch
For
ce,
kip
ExperimentUCSD Limit
Failure Load Error
Experiment 1.33 kip NA
UCSD Model 1.32 kip -0.750%
Response 2000 (MCFT)
1.37 kip +3.01%
Publications
Journal– Kim, S. J., Holub, C., and Elnashai, A., “Analytical Assessment of the Effect of Vertical
Earthquake Motion on RC Bridge Piers”, ASCE Journal of Structural Engineering, (in review)– Holub, C., Kim, S. J., and Elnashai, A., “Aspects of Multi-Axial Pseudo Dynamic Testing of
RC Members”, Earthquake Engineering and Engineering Vibration, (to be submitted)– Holub, C., Kim, S. J., and Elnashai, A., “Behavior of RC Bridge Piers Subjected to Vertical
Earthquake Motion—Part 1: Experimental Framework”, Engineering Structures, (to be submitted)
– Kim, S. J., Holub, C., and Elnashai, A., “Behavior of RC Bridge Piers Subjected to Vertical Earthquake Motion—Part 2: Experimental Results”, Engineering Structures, (to be submitted)
Conference– Elnashai, A., Kim, S. J., and Holub, C., “Assessment of RC Bridges under Horizontal and
Vertical Earthquake Motion”, 3rd International Conference on Concrete & Development, Tehran, Iran, April, 2009
– Kim, S. J., Holub, C., and Elnashai, A., “The Analytical and Experimental Investigation of the Effect of Vertical Ground Motion on RC Bridge Pier”, 14th World Conference on Earthquake Engineering (14WCEE), Beijing, China, Oct, 2008
Report– Kim, S. J. and Elnashai, A., “Seismic Assessment Of RC Structures Considering Vertical
Ground Motion”, Mid-America Earthquake Center, Report No. 08-03, 2008. Download url: http://hdl.handle.net/2142/9454