Nonlinear dynamic analysis of the bridge bearing and genetic algorithm–based optimization for seismic mitigation

Seismic mitigation for bridges by the specific bearing with highly elastoplastic dissipaters is very important to ensure safety of superstructures exposed to earthquakes. To study the lateral vibration of the bridge bearing, a nonlinear dynamic model is developed while thoroughly considering highly nonlinear mechanical properties of the bearing in this article. The generalized-α method is specifically adapted to solve the nonlinear equations. Moreover, nonlinear behavior of the bearing is fully incorporated through direct path-following of the practical experimental hysteresis curve. The proposed method is validated through careful comparison between the dynamic simulation and the quasi-static experimental results. Mechanical responses of the bridge-pier system under earthquake excitations can be calculated in a more reliable manner. On this basis, a parametric optimization model involving several key parameters of the bearing-pier system is developed. The optimization problem is solved by the genetic algorithm as the searching tool. Numerical examples show that mechanical responses of the bridge-pier system subjected to the earthquake excitations can be effectively mitigated after parametric optimization. The extensive applicability of the proposed method is validated through finding the optimized parameters for the bearing when multiple different earthquakes are considered. Moreover, the accumulative energy absorption of the bearing is also considered to enhance the seismic performance of the bearing. This work provides a reliable way of dynamic performance prediction and seismic mitigation study of nonlinear bridge bearing under earthquake excitations given any complex experimental hysteresis curve.