Three-Dimensional Dynamic Response Analysis of Twin-Girder Bridge with Elastomeric Supports under Moving Vehicle Loads

在混合结构受到重视的同时，从桥梁体系设计、制造和施工合理化的角度来看，少梁公路桥也成为值得关注的问题。由于双梁桥桥面板的跨度比普通梁桥大，因此双梁桥在交通荷载作用下桥面板相对主梁的挠度可能大于普通梁桥。伸缩缝附近的相对挠度会引起交通振动引起的低频振动等问题，因此，不仅对主梁的响应，而且对板和腹板的行为，为研究移动车辆荷载作用下双梁桥的动力响应特性，对一座桥梁进行了三维动力响应分析。桥梁相互作用系统、8自由度车辆模型和壳单元有限元模型，这些模型的建立使桥梁的真实的结构更加清晰，分析结果与试验结果吻合较好。分析表明，当车辆通过伸缩缝时，由于弹性支座产生竖向位移，桥梁的加速度响应被放大，同时由于板跨较大，腹板的面外加速度响应也被放大。此外，还证实了腹板的固有频率分布在15 Hz和27 Hz之间。

While hybrid structures are paid attention to, highway bridges with small number of girders become noteworthy from a viewpoint of rationalization of bridge system in design, fabrication and construction. Twin-girder bridge's relative deflections of slab to main girders due to traffic loads may be greater than those of ordinal girder bridges, because slab's span length of the former is longer than that of the latter. The relative deflections near expansion joints can give rise to some problems like low frequency vibration due to traffic-induced vibration.Therefore, for not only the main girder response but also the slabs and web plates behavior, a three-dimensional dynamic response analysis of a bridge is carried out to investigate the dynamic response characteristics of a twin-girder bridge under moving vehicle loads in this research.In modeling a vehicle-bridge interaction system, 8-degree-of-freedom vehicle model and FE model with shell element, which are adopted to express the real bridge more clearly, are used The analytical results of bridge agreed well with the experimental results. It becomes cleared that, since elastomeric support displaces in vertical direction, acceleration responses of the bridge are amplified, when a vehicle passes the expansion joint of the bridge.Out of plane acceleration responses of web plates are also amplified due to the slab's long span. In addition, it was confirmed that natural frequencies of web plates are distributed between 15Hz and 27Hz.