A comparative study on inelastic seismic demands of friction damped and based isolated structures

This study addresses the nonlinear seismic response of the buildings retrofitted with a series of passive protective systems. Friction damper (FD) as an energy dissipation device and lead rubber bearing (LRB), friction pendulum bearing (FPB), and high damping rubber bearing (HDRB) as base isolators were considered. Two sets of steel buildings were used. The first one included three 5 storey frames and two 10 storey frames while the second one contained 3, 6, and 9-storey steel moment resisting frames. To study the application and effectiveness of different seismic protective systems in the buildings, four cases were adopted. The first case investigated the utilization of FD and LRB considering their design properties. The second and third cases examined the influence of design parameters of FPB (i.e., the isolation period T, effective damping ratio ß, and yield strength to weight ratio Fy/W) and HDRB (i.e., T, ß, and post-yield stiffness ratio λ), respectively. Finally, the fourth case compared the overall performance of the protective systems through the single and combined use of energy dissipation devices (i.e., FD) and base isolation devices (i.e., LRB, FPB, HDRB). The most favourable isolation parameters of the isolators and slip load of FD were utilized in the design of the structural protective systems. They are modelled using a finite element program, and evaluated by the nonlinear time history analyses through ground motion records. The results were discussed in terms of various engineering demand parameters. It was shown that single protective system could not always satisfy fully operational performance level while the combined systems effectively achieved for the case studied structures.