Near-Fault Ground Displacement for Seismic Design of Bridge Structures

Abstract eng:
When structures located near or across the faults, the effects of ground displacement as well as velocity and acceleration are crucial factors, since the faults produce both step-like static deformation and dynamic pulse-like ground motions. Moreover, the fling-containing time histories are necessary for the seismic analysis and design of bridge structures. As has been observed before, the static offsets can reach from several centimeters to 10 meters (e.g., the Chi-Chi earthquake), and strong ground motion velocity pulses may exceed 100 cm/s. Until now, as there is no concrete synthesis method of design ground displacement, numerical simulation of strong ground motions, emphases on input ground displacement in this study, for such near-fault conditions are very necessary. This paper proposes a hybrid method based on coupling of the stochastic Green’s function method and theoretical Green’s function method. This hybrid method considers both dynamic and static terms. For illustrating the application of this hybrid method, a simulation of one dip-slip fault model was conducted. The results well featured the near-fault ground motions of dynamic displacement with the fling-step. Furthermore, the procedure for seismic design of bridge structures located close or cross fault under multi-input of velocities and displacements, which are simulated by this proposed method is briefly introduced, and a simple 4-span bridge structure across a reverse surface fault was analyzed. The calculation results showed that the synchronized time-histories inputs lead to significant differences in the dynamic response of bridge, which provide a useful reference for the design guidelines for such near-fault bridge engineering.

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