Numerical modelling to simulate the seismic response of bridges with base rocking steel columns

The application of rocking concept in seismic resisting systems has gained noticeable attention in the recent decades. Despite the conventional systems in which the lateral deformation of a member is provided by the dislocation of material in critical regions, in the rocking systems it is provided by gap opening mechanism. Such rocking systems exhibit self-centering behavior due to the presence of gravity load and/or post-tensioning forces. This paper investigates the seismic response of a two-span bridge with a recently introduced base rocking tubular steel column. A 3D finite element (FE) model of the rocking pier was generated and verified with the experimental results of a rocking pier under lateral cyclic load. Nonlinear time history analyses are performed to investigate the seismic response of such a system. A 2D macro model using two-spring and multi-spring approaches is developed to replicate the obtained responses. It is shown that although a two-spring model is convenient to use, it cannot accurately predict the dynamic response of the system. The response obtained using the multi-spring approach is highly dependent on the characteristics of the springs. A nonlinear regression procedure has been developed and the spring parameters have been computed utilizing the genetic algorithm. Using this approach, it is demonstrated that multi-spring models can predict the dynamic responses of steel bridge rocking piers as predicted with a detailed FE analysis. © The 17th World Conference on Earthquake Engineering