Distribution of damper properties along the height and the plan for the seismic retrofit of plan-asymmetric RC frames

The purpose of this research is to investigate the effectiveness of different vertical and in-plan distributions of the damping coefficients of nonlinear viscous dampers for the seismic retrofit of existing buildings with plan-asymmetry. The different distributions were examined within a procedure proposed in literature for the design of viscous dampers applied to 3D plan-asymmetric buildings. In particular, simple distribution criteria, based on specific structural properties, were considered with the purpose to improve the design of the damping system in terms of cost without significant change of response. All the distributions were applied considering, for comparison, both a simplified and an extended design method, by neglecting or considering, respectively, the plan-asymmetry in the design. The effectiveness of the different distributions was examined by performing time-history analyses of a case study with different configurations of dampers adopting a nonlinear behaviour both for the viscous dampers and the frame members. The dampers were dimensioned considering that the structure can exceed the elastic limit, with the only condition to satisfy the prefixed performance limit. The considered case study is a two bay RC frame with six storeys and an irregular plan configuration. The examined response parameters were maximum interstorey drifts, residual interstorey drifts, peak floor accelerations and maximum damper forces.