The Dynamic Response Analysis Of Bridge-foundation Interaction System Under Earthquake Spectrums

Softsoil stratums widely exist in coastal and alluvial plain areas of China. The experience of the building damage cases in the previous earthquakes shows that, the effect of soft subsoil on seismic performance of building structures is very adverse. Thus, the studies on seismic response characteristics of bridge-foundation interaction system with soft soil stratum are very significant. At present, it is difficult for the seismic problem of interaction system to have a deep and comprehensive understanding and analysis only by using experimental and detectional techniques. However, due to their good compatibility for parameters extrapolating and complex boundary conditions, numerical simulation methods based on the sophisticated theoretical framework, are gradually becoming the effective technical means on the research of dynamic interaction system problem.On the basis of the characteristics and limitations of previous research results, the Mohr-Coulomb elastic-plastic constitutive model and the discontituous contact algorithm are adopted to simulate stress deformation of foundation and the non-continuous interface behavior between pile and subsoil in this paper. Dynamic elastic-plastic numerical analyses are conducted to analyze seismic response characteristics of bridge-foundation interaction system under horizontal seismic excitations. The effects of soil parameters and pile length on the bridge-foundation dynamic interaction system are discussed, which may provide guidance and reference to the bridge design and engineering practice. The main content of the paper are as follows:(1) In the first place, seismic computational analyses of free field are conducted by developing2-dimensional elasto-plastic FEM model. The characteristics of the Fourier specturms, the Power spectrums as well as the accelerational spectrums corresponding to seismic accelerations at typical positions of free field for a given case are analyzed. Furthermore, the effects of depths and thickness of soft subsoil on the seismic response of free field are summarized based on parametric computations.(2) In the other place, seismic computational analyses of interaction system of bridge-pile-foundation are conducted by developing2-dimensional elasto-plastic FEM model. The dynamic charcteristics of internal forces and deformations at typical positions of piles, piers, abutments as well as the other part of the interaction system of bridge-pile-subsoil under horizontal seismic excitations are elaborated. In addition, the effects of depths and thickness of soft subsoil and length of piles on the seismic response of interaction system of bridge-pile-subsoil are summarized based on parametric computations.