Seismic protection of the horizontally curved bridge with semi-active variable stiffness damper and isolation system

Seismic vibration due to earthquake can damage the curved bridges that are the main interconnecting component for traffic separation structures of the urban highway system. Failure of bridges during and after a seismic event is vulnerable as bridges are lifeline structures. This work investigates the application of semi-active variable stiffness damper for a seismic control of the horizontally curved bridge isolated with different passive devices. The main objectives of the study are to investigate the effectiveness of the hybrid system and to find the optimum hybrid system for the seismic control of the curved bridge with different control laws of a damper. The selected bridge is a three-span continuous concrete box girder supported on pier and rigid abutment. The bridge deck is modeled as a single spine beam and the supporting pier is modeled as linear lumped mass system. The bridge is excited with four different ground motions having different ground motion characteristics with all three-ground motion components (horizontal as well as vertical). The results of the analysis demonstrate that the use of semi-active variable stiffness damper with different isolators is very effective in controlling the response of the curved bridge. The combination of semi-active variable stiffness damper and lead rubber bearing can provide an effective way for overall seismic control of the curved bridge. The use of modified switching control law for damper is as effective as switching control law with less number of sensors.