Effects of presence of nearby structures on ground vibration attenuation along response line

本研究分为两个主题：第一个主题研究了相邻结构在行波激励下沿两个或三个结构附近响应线的振动衰减。考察了结构间的间距和方位对减振特性的影响，得出以下结论：在接近结构共振的低频范围内，结构周围的地面振动大于无结构的地面振动。在高频范围内，多个结构作用下结构下游响应点的振动比单一结构作用下的小。在结构与响应线成直角布置的情况下，结构运动激发的散射波与自由场中的波之间的相位差似乎在计算响应线上的振动时起着重要作用。在此基础上，提出了一种将车辆动荷载按傅维叶级数展开，并将简谐荷载的解乘以荷载的频率分量来叠加的路旁地面振动的近似计算方法。对几个算例的应用结果表明，动载的移动效应出现在距车道较近的测点上。然而，随着与车道的距离变大，这种效果会迅速衰减。

This research is divided into two subjects.In the first subject, the vibration attenuation along a response line established near two or three structures is studied when excited by traveling waves from an adjacent source. The following is observed after the examination of the effect of the separation distance and orientation between structures on the characteristics of the vibration attenuation. The ground vibration around structures becomes larger than the vibration of ground without structures at low frequency range near the resonance of structures. In the range of high frequencies, the vibration of response points located downstream of the structures in case of multiple structures becomes smaller than the one in case of single structure. In case that structures are arranged at the right angle to a response line, it seems that the phase difference between the scattered wave excited by the motion of structures and the wave in the free field plays an important role in the assessment of the vibration along the response line.In the second subject, a thin-layred element and discrete wavenumber method is applied to simulate the ground vibration by a moving harmonic load. Moreover, an approximate method is proposed to calculate the ground vibration at a wayside in which a vehicle dynamic load is expanded in the Fouvier series and the solutions for harmonic loads are superposed by multiplying them by the frequency components of loads. As the results of the application to several examples, it is found that the moving effect of a dynamic load is appeared at measuring points in the near distance from the traffic lane. However, this effect decays rapidly as the distance from the lane becomes larger.