Effect of the Friction Force at the Movable Supports on the Seismic Performance of Continuous Bridges

Currently, design of continuous bridges normally takes into account the dynamic restrain provided by fixed support without considering the friction force at the movable supports to simplify the design calculation. Nevertheless, the energy dissipation at movable supports can be significant in assessing the dynamic behavior of continuous bridges under certain conditions. A comprehensive study is conducted to investigate the contributing factors to friction forces at movable supports and their influence on seismic response of continuous bridges. A nonlinear 3-D Finite Element Analysis (FEA) is performed to simulate the seismic performance of a six-span box girder concrete continuous bridge. Three models are chosen to simulate the common analysis models of continuous bridges. The time-history analysis is performed based on the response spectra of three earthquakes: N-S component of the El Centro earthquake (1940), Taft earthquake (1952), and Tianjing earthquake (1976 Ninghe earthquake, Tianjing, China). Effect of parameters such as friction coefficients, pier diameter, and initial shear stiffness of supports on the seismic performance of bridges are studied. The results show that the natural period of continuous bridge could be close to the dominant period of the subsurface soil. It significantly increases the dynamic response of bridges. Based on the results of this study, seismic design recommendations for continuous bridges are proposed.