Torsional seismic response control of asymmetric-plan systems by using viscous dampers

A new approach to locating viscous dampers optimally is herein presented in order to control the torsional seismic response of asymmetric-plan buildings. Firstly, the effects of the plan-wise distribution of supplemental damping on torsionally dynamic behavior have been investigated by using modal analysis techniques in the state space representation in order to highlight the main physical aspects of the problem. Optimal design criteria have then been carried out by evaluating the H∞H∞ and H2H2 norms of the transfer function relating the maximum edge displacement to the input seismic excitation. These norms represent suitable performance indexes to investigate the optimal plan-wise distribution of extra-structural dampers by means of parametrical analysis on varying the dynamic characteristics of the asymmetric-plan system. The numerical constraints on the mechanical parameters related to the practical application of the proposed control strategy are taken into account. Simple design formulae to model the results for the H2H2 norm are proposed and positively verified through broad numerical experimentation which compared the seismic response of asymmetric systems to synthetic and real excitations for different design strategies in a plan-wise arrangement of supplemental damping.