Effect of dampers on dynamic behavior of structures allowed to uplift

In this paper, to investigate the effect of elasto-plastic dampers attached at the base of structures allowed to uplift, the equation of motion is derived for incipient uplift motion and decomposed into modal equations. Two sets of modes are used during uplift, which correspond to elastic and plastic states of the damper. The initial conditions for each elastic or plastic state are derived in the modal coordinates. The dynamic behavior is analyzed by the proposed modal technique for initial velocity. From the results, conclusions are summarized as follows: (a) Vibration with high frequency caused by the second mode cannot be so much attenuated by the damper. (b) The maximum base shear is not so affected by the yield force of the damper. This is inexplicable from the static curves.