ABSTRACT
A semi-analytical approach is presented for the analysis of three-dimensional ground vibrations induced by trains traveling over a multi-span elevated bridge with pile foundations. The train is modeled as two sets of moving loads, with one accounting for the front wheelsets and the other for the rear wheelsets, the bridge as a series of elastically supported beams, and the ground as a viscoelastic halfspace. By the present semi-analytical technique, the entire vibration problem is divided into three subproblems, each dealing with the dynamic behavior of the superstructure of the bridge, the interaction between the bridge foundations and surrounding soils, and the wave propagation through the halfspace by point sources. Extensive parametric studies were conducted to evaluate the influence of some key parameters on the ground vibrations caused by moving trains. The numerical results indicated that train-bridge resonance can result in drastically amplified ground responses, which decay in an oscillatory manner as the site-to-bridge distance increases. Moreover, there exists a saturation phenomenon in the ground acceleration response spectra when the train speed exceeds a certain limit. In addition, a comparatively lower level of ground vibrations exists for certain combinations of bridge girder span length and train speed, which suggests the existence of some optimal designs for the bridge concerning mitigation of train-induced ground vibrations. Finally, the effect of elastic bearings of the bridge on the ground responses to the moving trains is also studied.
