Effects of Vehicular Loading on Seismic Load of Highway Bridges

对桥梁-车辆系统进行了动力地震分析，研究了车辆荷载对公路桥梁地震荷载的动力效应。本研究得出的主要结论如下。(1)建立了桥梁-车辆系统的动力学模型。在特征分析和频率响应分析的基础上，明确了“共振模态”和“动力衰减模态”的存在。前者是车辆荷载趋于增加桥梁地震荷载的情况，而后者则相反。(2)通过对桥梁-车辆系统地震反应的时程分析，阐明了桥梁-车辆系统共振模态或减振模态发展的物理过程。(3)得到了主要反应量（位移、转角、弯矩和剪力）的最大值，并讨论了它们的特性，重点讨论了车辆荷载对桥梁地震反应的影响。(4)定量地讨论了车辆荷载对公路桥梁地震荷载的放大/衰减效应，并提出了描述这种效应的简单物理参数。

Dynamic seismic analysis of bridge-vehicle system was performed, from which the dynamic effects of vehicle loading on seismic load of highway bridges were studied. Major conclusions derived from this study are as follows.(1) Dynamic models of a bridge-vehicle system has been developed. On the basis of eigen-analysis and frequency-response analysis, the existence of "resonance modes" and "dynamic reduction modes" has been made clear. The former are cases where the vehicle loading tend to increase the seismic load of bridges, and the latter, vise-versa.(2) From the time history analysis of seismic response of bridge-vehicle system, details of the physical process have been clarified regarding the development of the resonance modes or the vibration reduction modes.(3) Maximum values of major response quantities (displacement, angle of rotation, bending moment, and shearing force) have been obtained, and their characteristics were discussed with emphasis on the effects of vehicle loading relative to the seismic response of bridge alone.(4) Amplification/reduction effects of vehicle loading on seismic loads of highway bridges have been discussed quantitatively, and simple physical parameters have been proposed as descriptors of these effects.