Seismic response control of bridges by variable dampers

This paper discusses a variable damper proposed to control bridge response against an earthquake. The variable damper changes its damping coefficient depending on the structural response so that it functions as a passive energy dissipator, a damper stopper at small deck displacements, and a stopper with shock absorber for excessive deck displacements. The effectiveness of variable dampers is studied first by analytical simulations. It is demonstrated that the peak deck displacement and acceleration are reduced to 26% and 44%, respectively, of the bridge response without control. A prototype variable damper with a maximum damping force of 200 kN is developed, and its effectiveness is studied by a series of dynamic loading tests. A series of shake-table tests is also performed using a model bridge with a deck weight of 390 kN. It is found that providing the prototype variable damper reduces the deck response acceleration and displacement from 376 cm/s 2 and 9.2 cm to 203 cm/s 2 and 1.3 cm, respectively. Analytical simulation of the experimental results is made. The predicted deck responses are quite close to the measured ones.