Seismic Vulnerability Analysis Of Skew Bridge Based On IDA

Due to the rapid development of expressway and city spatial transportation,skew bridges have been extensively built to meet the requirements of route.Previous earthquake damage shows that skew bridges are more easily damaged in earthquakes than those of straight bridges due to the complex load transfer mechanism.Through the development of more than twenty years,the theory of bridge seismic fragility analysis has become an important way to evaluate the seismic performance of bridge structures.But the research on seismic vulnerability of skew bridge is still at start stage.By adopting the method of seismic vulnerability analysis based on IDA,the effects of skew angle and near-field earthquakes on seismic vulnerability of skew bridges are systematically studied in this paper,the main contents are as follows:(1)Based on a large number of literatures,the research status of seismic performance of skew bridges and the seismic vulnerability of bridge structures are systematically summarized.(2)The basic theory and method of seismic vulnerability analysis based on IDA are introduced in detail,the intensity measure of ground motion and the damage measure of structure are discussed,and PGA is used as the intensity measure of ground motion,the section curvature is used as the damage measure of bridge pier,and the relative displacement ductility ratio is used as the damage measure of the bearing.(3)The influence of skew angle on seismic vulnerability of skew bridge have been studied.Through the seismic vulnerability analysis of bridges with different skew angle,it is found that the median earthquake intensity of the pier column,bearing and bridge system decreases gradually with the increase of the skew angle,that is to say,the pier column,bearing and bridge system are more vulnerable with the increase of the skew angle.(4)By comparing the seismic vulnerability of the different vulnerable members of the skew bridge,the vulnerability distribution of the whole bridge system is obtained.It is found that the median earthquake intensity of abutment bearing is lower than other vulnerable components at all damage levels,that is to say,the abutment bearing is the most vulnerable component of skew bridge.(5)By comparing the vulnerability curves of skew bridges under near and far field earthquakes,the effect of near field earthquakes on the seismic vulnerability of skew bridges is studied.It is found that the damage probability of pier column and bearing under near field earthquake is larger than that of far field earthquake,and the structural damage state,structural parts and skew angle have significant influence on the damage probability deviation.The results of this study provide a theoretical reference for the quantitative evaluation of effects of skew angle and near field earthquake on the seismic performance of skew bridge,which can be helpful for the design of similar skew bridge in the future.