肋拱桥地震反应特点分析

Seismic Response Characteristics of Rib Arch Bridge

利用反应谱方法和时程法,采用4种不同的地震作用输入方式,即顺桥方向、横桥方向、竖向3个方向分别单独输入地震作用以及3个方向同时输入地震作用,对两座不同类型的大跨度肋拱桥的地震响应进行了计算,重点分析了不同方向地震作用在主拱肋引起的主要内力。研究结果表明:横向地震作用对上承式肋拱桥主拱肋内力有较大影响,横向地震作用不仅引起拱肋的面外内力,还会在拱肋内引起较大的面内弯矩、剪力和轴力;肋拱桥抗震计算时,应沿顺桥向、横桥向和竖向3个方向同时输入地震作用;拱脚为肋拱桥的抗震薄弱部位,抗震设计时应特别关注。

The seismic responses of two long-span rib arch bridges of different types were calculated by using response spectrum method and time-history method with four different seismic input modes,i.e.inputting the response spectrum along longitudinal,transverse,vertical direction respectively,and the earthquake action in three directions simultaneously.The main internal forces of main arch ribs caused by seismic action in different directions were analyzed.It is found that the lateral seismic action has a great influence on the internal force of the main arch rib of deck ribbed arch bridge.The lateral seismic action not only causes the out-of-plane internal force of the arch rib,but also causes larger in-plane bending moment and shear force in the arch rib,especially the larger axial force.Therefore,in the seismic calculation of rib arch bridges,seismic action should be input along three directions of the bridge simultaneously,such as longitudinal,transverse and vertical direction.Arch foot is the weak part of the rib arch bridge in the aseismic design,and special attention should be paid to.