Civil Engineering Association

Seismic analysis of a three- span deck girder bridge

This paper presents seismic analysis of a three-span deck girder bridge. A finite element model to analyze the deck girder bridge has been developed by using finite element software called ANSYS. The entire work has been carried out in two steps. In the first step, a three dimensional model of the bridge has been subjected to equivalent static earthquake loading by following AASHTO guideline. In the second step, Response
Spectrum analysis has been performed. Then the design forces and moments at the column bases of the bridge are obtained by using the above two methods. Finally a comparative study of the design values has been performed between those two methods mentioned above. From the entire study it has been found that the magnitude of the axial forces are almost same in those two methods but the design moments and shear forces
vary significantly. In case of design moment, the result found from response spectrum method (RSM) is about
1.74 times of the design value obtained by equivalent static force method (ESFM). Therefore it can be said that there is a possibility of achieving under design of the bridge if follows the ESFM. Based on overall findings, it can be suggested that the response spectrum method should be performed for seismic load analysis of the bridge to achieve a safer design.