Seismic Response Of Long-Span Bridges Due To Strong Ground Motions

In recent years, many important long-span continuous rigid frame bridges are constructed in our country, their seismic responses of these bridges haven't be regulated in the criterion. It is known that the aseismic capability of the bridges is the key control factor. So the main purpose of this research is trying to study the seismic response of long-span continuous frame bridges by Finite Element MethodThe differences between this research and the former are that we estimated the near fault ground motions as the seismic inputs for long-span bridge aseismic response calculation. The near-fault ground motions are more complex than far field usually, the typical one is the velocity pulse in accelerograms shown in many recordings in past earthquakes;the amplitude and phase differences among recordings in bridge piers are also important aspects.The FEM program is Ansys, we create the bridge model by space beam, and make the bridge models with different spans, piers, and height. After calculating, we get the response of these bridges under Taft, El Centro, Tianjin and Jiji waves, along the bridge and across the bridge respectively. And also we compare the internal force of the key sections and find the sensitive parameters, and consider different speed of traveling wave to one of the models and find the rule of the situation.Meanwhile, the curve rigid frame bridge and its FEM model is constructed, then the internal force of the control section is calculated by adopting the near fault ground motion from different directions. The affection of wave passage effect on curve rigid frame bridge is also analyzed .We study how the pier's height affects the bridge dynamic performances considering both soil-structure interaction and NOSSI. In the end, we summarize the rule of curve rigid frame bridge under near ground motion.From the study of straight- and curve- rigid frame bridge under different ground motions, especially near ground motion, we give the suggestions for solving the related problems in actual engineering projects.