Study On Dynamic Performance Of Railway Bridge With Considering Topographic Effect

As Bridge is as an important part of the lifeline project, its anti-disaster capacity is particularly important. Previous earthquake shows that topography has some amplification effect. So it is particularly critical to consider topographic effects while analyzing the eismic performance of bridge. However, the research on existing bridges about its dynamic performance and vulnerability does not consider this problem perfectly. In view of this situation, the main work of this paper is as follows.1. It briefly describes the background of this topic, and analyzes the characteristics of bridge damage. It describes the dynamic viscoelastic artificial boundary and development of bridge seismic vulnerability analysis.2. Based on the input method of equivalent forces of ground motion, this paper builds two-dimensional models of three types of sites--oncave valley, level ground, convex ridges, and it analyzes the distribution of site model under earthquake while P waves and SV waves oblique with four kinds of angles comparatively. It is pointed out that concave valley’s amplification effect is more obvious than the other two venues. It should be taken into key considerations in seismic design.3. Based on the viscoelastic artificial boundary conditions, this paper studies the input method of equivalent forces of ground motion in three-dimensional model, and builds three-dimensional models of concave valley and level ground. Besides, with P waves and SV waves obliquing, displacement-time curves of observation points on the surface of the site is used as seismic response and is then applied to a continuous beam bridge model of a span high speed railway, thus Influence of parameters such as topography, Seismic waveforms and the angle of incidence is analyzed parallelly. It is concluded that the dynamic response of pier near the foot of the slope is stronger than other piers and that on pier top the relative displacement of fixed restraint pier is greater than other pier.4. This paper studies the current situation of bridge vulnerability analysis, and defines the displacement ductility ratio as damage index. In this paper, continuous beam bridge fixed constraint piers is chosen for the study,10natural seismic waves are chosen as Incident waves, which will oblique the concave valley and level ground at different Incident angles. Then the80displacement-time curves obtained from observation point on the surface of the two venues are used as earthquake response. And it is applied to the bottom of the fixed pier, thus drawing fragility curves. Finally the fragility curves at the two venues are compared for analysis.