The effects of earthquake incidence angle on the seismic fragility of reinforced concrete box-girder bridges of unequal pier heights

The effects of earthquake incidence angle on the seismic fragility of highway bridges of unequal pier heights are investigated. A variety of configurations from regular to so-called highly irregular models are considered. In order to accurately quantify the uncertainties in the modeling process, the most influential sources related to the material properties, earthquake characteristics and structural geometries are considered in the nonlinear simulation. Several three-dimensional bridge models are simulated in OpenSees platform, and a set of strong ground motion records are employed in a series of nonlinear time history analyses of the bridge models. Different incidence angle of the records have been used to investigate the response of the models and to extract the most critical engineering demand parameters. The system and component fragility parameters are developed and compared for different values of the excitation angles for all the bridge models. Given the wide range of variables used here, a conversion coefficient is proposed to convert the bridge response for different incidence angles to critical response.