The Study On The Seismic Behavior Of Prestressed Concrete Skew Continuous Box-girder Bridge

On the highway, the number of skew bridges can reach 40% to 50% of the entire line of the total number of the bridges. Under the seismic action, skew bridge occurs in different damage degrees, therefore, in-depth study of skew bridge on seismic response and seismic fragility is essential in order to provide scientific basis for earthquake relief and aseismic strengthening of bridge. This paper takes a common skew continuous box girder bridge of our country highway as engineering background, combined with the development and present situation of domestic and foreign skew bridge seismic research. This paper gives a systematic study on the seismic response and the seismic fragility of pier which is the most vulnerable member in a skew continuous box girder bridge on vertical and horizontal ground motion,making us a comprehensive understanding of bridge seismic fragility analysis process. And study the influence of changes of skew angle on the seismic response and seismic fragility.The main contents of this paper include:(1) Firstly,the seismic damage phenomenon of the highway bridge and the status quo of its seismic research at home and abroad are comprehensively described.Then the research methods and the present situation of seismic fragility of bridges are introduced in detail.(2) Based on the actual engineering, the structural dynamic model of the skew box girder bridge is established by using the finite element analysis software called Midas Civil. The dynamic characteristics of the structure are obtained by the eigenvalue analysis, including the vibration mode shape, natural cycle and natural frequency. and compared with the orthogonal bridge, the impact of changes of skew angle on the dynamic characteristics of the structure is explored.(3) The basic concept, basic assumption and analysis method of response spectrum theory are introduced. Through E1 and E2 seismic response spectrum analysis, the vertical seismic action and lateral earthquake action are respectively studied.(4) The paper introduces the input of seismic wave and the determination of damage index. Through the nonlinear time history analysis of the dynamic finite element model, the fragility curves of piers are obtained. and by analyzing parameter, the influence of the change of skew angle on the vulnerability curve is investigated.