r - The Hong Kong Polytechnic University

Acceleration (g)
1
0.5
0
-0.5
Simulated
Initial
Sa (g)
4
3
2
1
Response
Initial
Code
-1
0 10 20 30 40 50 60 70 80 90
Time (sec)
Figure 11 Seismic wave and response spectrum of the artificial ground acceleration for pseudo-dynamic test
Test Results and Conclusions
0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Period (sec)
Figures 12 to 15 present the failure modes and hysteresis curves of column P3, P4, and P2, respectively. Though
given different boundary conditions and different detected material strengths, three columns demonstrate similar
flexural failure mode, especially the backbone curve can be simplified as a bi-linear curve. The maximum lateral
force is around 1000 kN, and the displacement ductility can reach 5.0. Besides, for each column, it is due to
large spacing of 20cm of lateral reinforcement, the longitudinal reinforcements were buckled and large cover
concrete blocks were spall off during the tests. Moreover, the lap splice length of lateral reinforcement is
insufficient and lacks of seismic hook, leading to separation of lateral reinforcement observed at some particular
heights in the plastic hinge zone. However, the axial load obtained from the design drawing and calibrated by
the system identification is 291tonf, a relative small value about 0.04-0.05 f’cAg, as a result to explain why the
bridge column performed ductile behaviour, compared to the conventional axial load of 0.15f’cAg on the
reduced-size columns in the lab. In addition, the test results are not sensitive to the scouring of caisson
foundation, since the geological condition is gavel. Figures 12 to 14 also show the analytical results, both from
pushover analyses and cyclic loading analyses, by using the program SERCB for Bridge, developed by NCREE
in 2010. This program has been used as a standard tool in current seismic evaluation and retrofitting program in
provincial bridges in Taiwan since 2009. The analytical results are agreed with the experimental result very well.
Based on the results, it is suggested to utilize Mander model for confined concrete model and TAKEDA
hysteresis model with an adequate plastic hinge length proposed by Priestley, so that to simulate a
flexural-failure dominated column if strength degradation and stiffness reduction are not obvious.
Drift ratio (%)
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Drift ratio (%)
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
1250
125
1500
150
1000
P3 COLUMN
100
1200
P3 COLUMN
Experimental result
120
750
75
900
Pushover curve
90
500
50
600
Hyeteresis loop
60
Lateral Force (kN)
250
0
-250
PULL
PUSH
25
0
-25
Laterl force (tonf)
Lateral Force (kN)
300
0
-300
PULL
PUSH
30
0
-30
Laterl force (tonf)
-500
-50
-600
-60
-750
-75
-900
-90
-1000
-100
-1200
-120
-1250
-125
-1500
-150
-600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600
Lateral Displacement (mm)
-600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600
Lateral Displacement (mm)
(a) failure mode (b) hysteresis loop (c) analytical results
Figure 12 Experimental and analysis results of P3 column
Drift ratio (%)
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Drift ratio (%)
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
1250
125
1500
150
1000
P4 COLUMN
100
1200
P4 COLUMN
Experimental result
120
750
75
900
Pushover curve
90
500
50
600
Hyeteresis loop
60
Lateral Force (kN)
250
0
-250
PULL
PUSH
25
0
-25
Laterl force (tonf)
Lateral Force (kN)
300
0
-300
PULL
PUSH
30
0
-30
Laterl force (tonf)
-500
-50
-600
-60
-750
-75
-900
-90
-1000
-100
-1200
-120
-1250
-125
-1500
-150
-600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600
Lateral Displacement (mm)
-600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600
Lateral Displacement (mm)
(a) failure mode (b)hysteresis loop (c) analytical results
Figure 13 Experimental and analysis results of P4 column
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