Modeling and analysis of a three spanned concrete Deck girder bridge under seismic loading

This research paper presents the results of a research work aimed at the analysis of a three-span concrete deck girder bridge under seismic loading. A finite element model to analyze the deck girder bridge has been developed by using finite element software ANSYS. This research 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 code. In the second step, Response Spectrum analysis has been performed. Then the design forces and moments at 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. From the study it has been found that the magnitudes of the axial forces are almost same in 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 from equivalent static force method (ESFM). Therefore it can be said that there is a possibility of achieving under design of the bridge if the seismic analysis 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 more reliable and safer design.