Performance-based design of added viscous dampers using capacity spectrum method

The conventional practice of carrying out a series of trial and error process for design of supplemental dampers requires a lot of computation time and labour. In this study a straightforward design procedure for viscous dampers was developed based on capacity spectrum method in the context of performance based seismic design. The required amount of viscous damping to satisfy given performance acceptance criteria was evaluated from the difference between the overall demand for effective damping and the inherent damping plus the equivalent damping capacity of the structure originated from plastic deformation of each structural member. The proposed method was applied to single-degree-of-freedom systems with various design parameters such as natural period, yield strength, and the stiffness after the first yield. The procedure was also implemented to 10- and 20-storey steel frames for verification of the proposed method. According to the earthquake time history analysis results, the maximum displacements of the model structures with viscous dampers supplied in accordance with the proposed method correspond well with the given target displacements.