Prediction And Parameters Research On Viaduct Train-induced Environmental Vibrations

With the development of economy and society, the urbanization expands and the population increases continuously. The rail traffic, due to its advantages, has been developed at a fast speed and the construction of rail traffic system reaches a peak period. However, the vibration influence on nearby environment induced by rail traffic is becoming more and more serious, which has been paid more and more attention. Viaduct is one of the main load-bearing systems of rail traffic and has many successful applications. Therefore, it is very important to study environmental vibration induced by trains running on the viaduct.The prediction of environmental vibration and its influence factors have been studied in this dissertation on the basis of train-bridge-ground numerical model and the analysis of some influencing factors. The prediction formula of environmental vibration induced by viaduct trains have been obtained and furthermore validated by the experimental results. The main contents include:(1) The dynamic response of simply-supported beam with elastic support is studied. The functions of mode shapes for those beams with elastic support are achieved by theoretical deducing. Furthermore, the dynamic responses of simply-supported beam with elastic support under different loads are studied. The loads include vertical moving load, vertical and horizontal moving load together, moving spring-damping system and moving load with evenly variable velocity. The numerical calculation is carried out by means of the theoretical formulation and some valuable conclusions are drawn up.(2) The in-situ experiment of environmental vibration is carried out on the viaduct part of Beijing Metro Line 5. The measured data are analyzed in time domain and frequency domain, respectively. The following conclusions are obtained:the ground vibration near pier for normal track is larger than that for ladder track; the ground vibration far from the pier for normal track is smaller than that for ladder track; the propagation characteristic of horizontal ground vibration shows increasing tendency firstly and then decreasing tendency; the propagation of vertical ground vibration shows the tendency of decreasing continuously; there appears an obvious renounced region and the phenomena is more obvious with the increasing of vibration level; the ladder track has the effect of decreasing some vibrations at certain frequency range and however increase some vibration at another different frequency range; the attenuation of those vibrations with high frequency is faster than that with low frequency; the vibration of far field is mainly caused by those vibrations with low frequency.(3) The numerical model of vibration induced by viaduct trains is established. The model includes train-bridge sub-model and pier-soil sub-model. By establishing vibration source model of train-bridge, the load acting on the top of pier can be calculated. Then the force on the top of pier can be applied to a 3D pier-soil model established by FEM software. Finally, the vibration response of any point on free field can be calculated. In the FEM model are taken into account several influence factors including rail irregulation, train speed, soil parameters, bridge span and distance to pier.(4) The prediction model of environmental vibration induced by viaduct trains is obtained based on calculated results by means of regression method. The prediction model is validated by the experimental data, and the conclusion show that the model has high adaptation and accuracy.