Seismic Response Of Simply-Supported Girder Bridge Subjected To Near-Fault Pulse-Like Ground Motion

In recent years, near-fault ground motion is one of the hottest problems in earthquake engineering and structural engineering.Because of their special pulse effects, it has been proven that infrastructure system in near-fault zone faces the higher seismic risk than that of far from fault. Although most of architecture can been built avoiding the fault, some of them,particular the lifeline system,will have to pass through the fault system due to structural characteristics or land utilization.It is very necessary to study the seismic response mechanism of architecture and building near the fault system, particular with the effect of near-fault pulse-like ground motions. To explore the seismic response characteristics and explain some earthquake damage characteristics of bridges near the fault zone,this paper studies the seismic response analysis of simply supported girder bridge subjected to near-fault pulse-like ground motion. The main contents in this study includes as follow:Firstly, the characteristics of near-fault pulse-like ground motion are analyzed to study the mechanism of the near-fault pulse.Three types of ground motions near fault and their response spectrum, near-fault pulse-like ground motions with forward directivity effect, pulse-like ground motions with fling step effect and ground motions without pulse are systemically analyzed.Secondly, two China's seismic codes about bridges-"Code for Seismic Design of Highway Engineering" JTJ004-89 (hereinafter referred to as 89 code) and "Highway bridge seismic design details" JTG/TB02-01-2008 (hereinafter referred to as 08 code) are studied on the topic related the near-fault strong motion. Compared to 89 code,it is found that 08 code is more reasonable, more detailed and comprehensive in consideration of the near-fault defenses, more comprehensive in approach. But there are also difficulties in the 08 code in performance-based seismic design, in a more comprehensive consideration of near-fault ground motion effects as well as the source mechanism.Thirdly, build the analysis model of Sichuan Yingxiu Minjiang Bridge. Using numerical methods, we analyze the nonlinear response characteristics of the bridge subjected to near-fault pulse-like ground motions with forward directivity effect,fling step effect and ground motions without pulse respectively.It can be found that the effects of near-fault pulse-like ground motion play a special role in what cause the failure phenomena of the Minjiang Bridge.Lastly, verifying the applicability that simply supported girder bridge with lead rubber bearing subjected to pulse-like ground motions.It's found that simply supported girder bridge with isolation bearing, still can play a role in reducing the damage to the bridges,even when it is subjected to near-fault pulse-like ground motion. The results show that some of the parameters of the isolation bearing should be optimized to achieve the best isolation effect.