Effect of Nonlinearity in Pier and Well Foundation on Seismic Response of Bridges

Abstract eng:
Nonlinear seismic analysis of soil-well-pier system of a typical bridge supported on well foundation is carried out considering nonlinearity in piers and well. Bi-linear kinematic element is used to model nonlinearity in piers and well. Separation at the interface of soil and well is considered using compression-only gap elements. Analyses have been performed in two steps. In the first step, for a given acceleration time-history onedimensional free-field analysis of the site is performed using SHAKE2000 to obtain the motion at the base of the soil profile. In the next step, this motion is applied at the base of finite element model of soil-well-pier system in SAP2000. The analysis has been carried out for different values of depth of scour and for two different earthquake motions in longitudinal direction. It is found that bending moment demand exceed the capacity by 20% to 70% in piers and 30% to 75% in well when piers and well are assumed to behave linearly. Subsequently, nonlinearity in piers is introduced when well is considered as linear. The analysis results show that nonlinearity in piers does not considerably reduce the force response of well. Therefore, nonlinearities in both piers and well are introduced in the next step. In this case, 15% to 50% reduction in rotational ductility demand in piers is observed but now the well must have adequate rotational ductility.

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