弹性连接失效对大跨斜拉桥地震响应影响

Influence of Failure of Elastic Connections on the Seismic Response of Long-Span Cable-Stayed Bridge

首先,以附加弹性连接(elastic connection,简称EC)的线性单自由度(single degree of freedom,简称SDOF)系统为例,研究弹性连接的失效对系统动力时域响应的影响;其次,以一座半漂浮体系的大跨斜拉桥在两组地震作用下的地震响应为例,研究塔(墩)梁间弹性连接失效对大跨斜拉桥结构地震响应的影响。研究表明:弹性连接失效对大跨桥梁动力响应存在重要影响,动力响应存在明显差异;考虑弹性连接失效后,如果在地震中弹性连接出现失效,大跨斜拉桥加劲梁地震内力明显小于未考虑弹性连接失效的情况,但加劲梁和塔顶纵桥向位移会有所增加;应当设置合理的弹性连接及其失效限值,保护主体结构在地震中的安全。

As to long-span cable-stayed bridge with floating or half floating girder-tower style,researches reveal that proper elastic connects(EC)between tower(pier)and girder placed in longitudinal direction of the bridge can reduce the displacements between tower(pier)and girder and cause reasonable distributions of earthquake load in longitudinal direction.Firstly,the dynamic responses under complex loading in time domain of single degree of freedom(SDOF)attached with EC are studied to investigate the influence of EC on the dynamic response of SDOF.Secondly,a long-span cable-stayed bridge with half floating girder-tower style is taken as an example to investigate the influence of failure of EC on the seismic response,under two earthquake motions.It is found that the failure of EC has important effects on the dynamic response of long-span bridges and significant dynamic responses exist.If the failure of EC happens during the ground motion,the internal force of girder is much smaller when the failure of EC is considered than that of failure of EC is not considered,however the displacements of girder and top of the tower in longitudinal direction may increase significantly.ECs should be designed with reasonable failure limits to protect the main structures of the bridge during the earthquake.