Control of Earthquake Induced Vibrations in Asymmetric Buildings Using Passive Damping

This paper summarizes the results of a recent investigation on the dynamic response of asymmetric-plan buildings with supplemental viscous damping to harmonic ground motion using modal analysis techniques. It is shown that most modal parameters, except modal damping ratios and dynamic amplification factors, are affected very little by the plan-wise distribution of supplemental damping in the practical range of system parameters. The first modal damping ratio increases while the second decreases as CSD moves from right to left of the system plan, and their values increase with larger plan-wise spread of the supplemental damping. Trends for the dynamic amplification factors are reversed, as they are inversely influenced by the damping ratio, i.e., higher the damping lower the dynamic amplification factor. The largest reduction in the flexible edge deformation occurs when damping in the first mode is maximized. Introduction A research program has been designed to systematically investigate the seismic behavior of linearly-elastic, one-story, asymmetric-plan systems with supplemental viscous damping devices. First, three additional system parameters were identified: the damping ratio due to supplemental damping devices, sd ζ ; the normalized supplemental damping eccentricity, sd e ; and the normalized supplemental damping radius of gyration, sd ρ . Next, the effects of these parameters on the flexible and stiff edges of asymmetric-plan systems subjected to a selected earthquake ground motion were investigated. It was shown that supplemental damping reduces edge deformations, and that the degree of reduction strongly depends on the plan-wise distribution of the supplemental damping. Results of this research were reported earlier (Goel, 1997).