Pushover Analysis and Dynamic Response under Earthquake for a Continuous Rigid Frame Bridge

Abstract

Abstract. Based on the concept of energy design, pushover analysis and elastoplastic dynamic response have been made under the earthquake. It is seen that the loading mode plays an important role in the pushover analysis. The loads in the pushover analysis distribute along the height of the structure that should reflect the distribution of the inertial forces under the earthquake so that the calculated displacements have a good accuracy in contrast to the real displacements. Only in such a way, the result by pushover analysis method is credible. On the other hand, it is found that the high order vibration modes can not be neglected in the pushover analysis for a continuous rigid frame bridges with long span and high piers. However, the bridge design codes have not told how to consider the effect of high order vibration modes. A simplified loading mode is then proposed in this work. A contribution ratio of vibration mode is defined to indicate whether the vibration mode should be considered or not in the pushover analysis. The proposed loading mode is applied to a real continuous rigid frame bridge with large span and high piers. The dynamic response and aseismatic property are evaluated and discussed. In addition, the results by pushover analysis are compared to the results by non-linear time-history analysis. The result shows that the high order vibrational modes indeed have a pronounced influence on the result. The proposed loading mode can give a reasonable result.