大跨度异型钢管混凝土拱桥典型病害分析及支座脱空影响研究

Typical diseases of long-span concrete filled steel tube arch bridges and the effects of the void of supports

大跨度异型钢管混凝土拱桥在使用过程中易出现车致动力响应大等不利情况,现阶段造成该类型桥梁车致动力响应显著的病害及其影响尚不明晰。以某典型大跨度异型钢管混凝土拱桥为研究对象,对该桥的典型病害进行了调查,基于现场测试与理论分析,对该桥的典型病害及支座脱空病害的影响进行了研究。现场调查及测试结果表明:支座脱空会引起主梁伸缩缝两侧的差异沉降,导致桥梁受力状态变化,加剧车辆对主梁和吊杆的冲击作用。现阶段钢箱梁伸缩缝附近和跨中位移冲击系数分别达到了1.52和1.15,吊杆力应力幅变化率为-28.0%~18.5%;数值分析结果表明:支座脱空后钢箱梁和吊杆的车致动力响应变化显著;支座脱空将导致该桥主梁明显的顺桥向位移,且与主梁竖向位移达到了相同量级;支座脱空后钢箱梁车致加速度峰值会显著增加,且当车辆荷载作用下支座与钢箱梁仍能发生相互碰撞时影响更为显著;支座脱空后吊杆力应力幅变化显著,且其对短吊杆影响更显著;支座脱空是造成该类型桥梁钢箱梁、吊杆等构件车致冲击响应显著变化的重要原因之一。

Long-span concrete filled steel tube(CFST)arch bridges often suffer from serious vehicle-induced dynamic responses during service,but the reasons and effects of certain remarkable vehicle-induced dynamic responses are not yet deeply explored.Taking a typical long-span CFST arch bridge as a research object,its typical diseases were investigated.Based on the field testing and theoretical analysis,the typical diseases and the effects of supports void were studied.The field investigation and test results show that the void of main girder supports causes differential settlement on both sides of the expansion joint,and aggravates the vehicle impact on the main girder and suspenders.The impact factors of displacement near the expansion joint and midspan reach 1.52 and 1.15 respectively.The variation rate of stress amplitude in suspenders is between-28.0%and 18.5%.The numerical results show that the vehicle-induced dynamic responses of the steel box girder and suspenders change significantly before and after supports get void.The void of the supports causes obvious along-bridge displacement of the main girder,which may reach the same magnitude as the vertical displacement.The peak value of vehicle-induced acceleration of the steel box girder increases significantly after supports get void,and the impact will be more significant when the supports and steel box girder are still able to collide with each other under vehicle load.The stress amplitude in suspenders changes remarkably after the supports get void,and its effect on short suspenders is more obvious.The void of supports is one of the main reasons for the significant change of vehicle-induced impact responses of the steel box girder,suspenders and other components of this type of bridge.