Seismic Response of An Isolated Curved Bridge Considering Bi-Directional Effects
Bridges with curved configurations are important in modern highway systems and are gaining popularity at complicated interchanges or river crossings where geometric restrictions and constraints of limited site space make extremely difficult for adoption of standard straight superstructures. Curved alignments offer, in addition, the benefits of aesthetically pleasing, traffic sight distance increase, as well as economically competitive construction costs with regard to straight bridges. Curved configurations may sustain severe seismic damage owing to rotation of the superstructure or displacement toward the outside of the curved line due to complex vibrations occurring during strong earthquake ground motions. The present methods for design of the bridge structure are mainly focused on determining the maximum response in a particular direction of the structure. Since the earthquake motion is randomly varied, the critical combination of the responses due to directional effect may not coincide with the maximum value of the uni-directional responses. Therefore, the effect of bi-axial interaction and efficacy of the prevailing design practice, considering a single component of earthquake motion along the principle directions of bridge, need to be investigated. In the present study, the seismic response of an isolated curved continuous bridge with high damping rubber bearings has been determined under uni-directional and bi-directional ground excitations, incorporating the interaction phenomenon in the bearings and piers. The response of the bridge, with different orientations of the major component of ground motion with respect to the axis of the bridge, has been obtained and compared with uni-directional responses. It has been observed that the response of the bridge has been significantly increased due to the effect of bi-directional excitation whereas the uni-directional analysis yield significantly underestimated results.
Index Terms— Curved bridge, isolation, high damping rubber bearing, bi-directional loading