An improved stochastic Green’s function method that using phase characteristics to simulate the directivity effect was proposed, in order to research the influence of the fault rupture process on the seismic response of seismic isolation bridges. Taking the fault conditions of the 1994 Northridge earthquake in the United States as an example, the effectiveness of the simulation method was verified by comparison with the actual seismic records. The improved stochastic Green's function method was used to simulate four groups of acceleration time histories with the same epicentral distance as the input conditions, and the effects of fault rupture process on the seismic response of seismic isolation bridges with the same epicentral distance and different directions were compared. Results show that the similarity between the duration envelope curve and the phase difference distribution can be used to simulate the acceleration time history of stochastic Green’s function conveniently. Under the same epicentral distance, the ground motion at the observation point in the fault rupture direction and the seismic response of the bridge structure at the corresponding position are significantly greater than those at the observation point in the non rupture direction. When the acceleration time history of ground motion in the rupture direction does not have pulse characteristics, the seismic response of seismic isolation bridges around the fault is mainly affected by the intensity of ground motion, and the influence of bridge orientation is not obvious.
Xu XIE,Wen-tong HUANG,Long-fei JI,Tian-jia WANG. Influence of fault rupture process on seismic responses of seismic isolation bridges. Journal of ZheJiang University (Engineering Science), 2021, 55(12): 2225-2233.
Fig.1Earthquake duration model of sub-fault rupture
Fig.2Phase difference spectrum and cumulative probability density distribution of small earthquake in sub-faust
Fig.3Stochastic Green function to simulate ground motion
Fig.4Fault and station location of Northridge earthquake
Fig.5Comparison and verification of simulation results of acceleration time history and response spectrum with actual records of three stations in Northridge earthquake
台站
实测/模拟
PGV/(cm·s?1)
PGA/(cm·s?2)
PGV/PGA/s
LV3
实测H1方向
8.43
82.53
0.10
LV3
实测H2方向
8.02
103.76
0.08
LV3
模拟
8.03
85.04
0.09
LV1
实测H1方向
7.81
87.14
0.09
LV1
实测H2方向
7.05
71.80
0.10
LV1
模拟
10.91
104.49
0.10
Tab.1PGV/PGA of station LV3 and LV1
Fig.6Bridge elevation layout
Fig.7Calculation model of bridge seismic response
Fig.8Observation location and simulation result of ground motion acceleration time history and response spectrum
Fig.9Displacement response of P4 pier top and hysteretic curve of E shape steel damper at P5 pier
Fig.10Adjusted ground motion of El Centro earthquake
${\rm{PGA} }$
$ 地震动 $
$|d^{{\rm{P4}}}_{{\rm{max}}}|$
$\eta ^{\rm{P5}}$
0.15g
El Centro
27.6
3.5
0.15g
15-2
21.7
2.5
0.15g
30-4
24.0
2.8
0.30g
El Centro
35.5
5.3
0.30g
15-3
26.2
3.8
0.30g
30-1
25.6
3.5
0.60g
El Centro
40.3
8.5
0.60g
15-1
43.9
10.2
Tab.2Comparison with displacement of pier top and plastic ratio of E shape steel damper under different seismic input
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