Study on Seismic Response of Horizontally Curved Bridges in Combination with Skewed Abutments

Abstract

The present study investigates the seismic response of skew-curved concrete box-girder bridges under free vibrations and forced vibrations. A bridge having in-plan curvature in combination with the skewed abutments is termed as skew-curved bridge. 3-D models of the bridge with varying configurations are generated in the CSiBridge. The curvature angle for the parametric study has been varied as 0°,30°,60° and 90° in combination with skew angles of 0°,15°,30°,45° and 60°. Modal analysis and response spectrum analysis for all the bridge models has been performed. Modal response of the various bridge configurations has been presented in graphical form in order to have knowledge of the mode shapes, time periods and fundamental frequencies of the bridges. Furthermore, mode participation factor for three orthogonal directions also have been determined for every configuration of the bridge considered. After performing response spectrum analysis, variation of out-of-plane bending moment, in-plane bending moment, and longitudinal torsion along with the span length under horizontal (i.e. longitudinal and transverse) and vertical component of seismic excitations has been also presented using graphical representation. Results indicate that increase in skew angle leads to decrease the time period ratios in first vertical mode of vibration. Time period ratios for first longitudinal mode are found to increases as the degree of skewness and curvature increases, whereas mode participation factor decreases with increase in curvature and increases with increase in skewness for the same mode. Mode participation factor of first transverse (in-plane) vibration mode increases with increase in both skew and curvature angle. Results of response spectrum analysis indicates that all the three principal moments experience higher moment demand under transverse components of seismic excitations. For skew-curved bridges moment demand gets increases with increase in curvature in most of the cases. However, increase in skew angle causes decrease in moment demand in most cases.