Effect of the distribution of damping coefficients along the height on the seismic response of RC frames retrofitted with viscous dampers

The main purpose of this research is to investigate the effects of different vertical distributions of the properties of nonlinear fluid-viscous dampers for the retrofit of existing multi-storey reinforced concrete frames. In particular, the different distributions are defined on the basis of the same value of the supplemental damping ratio. Since the viscous dampers are used for the retrofit of existing buildings, they are dimensioned assuming that the structure can exceed the elastic limit, with the only condition to satisfy the prefixed performance limit. In the design phase the different vertical distributions of damper properties are compared in terms of the total sum of the damping coefficients. The effectiveness of the different distributions is then examined by performing time-history analyses of several case studies considering a nonlinear behaviour both for the viscous dampers and for the structural members. The considered case studies are five RC frames characterized by different number of storeys and different properties in terms of regularity in elevation. The results of the nonlinear dynamic analyses are examined in terms of maximum and residual interstorey drifts, peak floor accelerations and maximum damper forces.