Simple design procedure of a friction damper for reducing seismic responses of a single-story structure

This study proposed a simple design procedure for determining the required damping force of a friction damper installed in a single-story structure. The analysis model was transformed into an equivalent mass-spring-dashpot system by approximating a nonlinear Coulomb damping force with an equivalent viscous damping force. A closed form solution for the dynamic magnification factor (DMF) for a steady-state response was derived using the energy balance equation. The equivalent viscous damping ratio was defined using the DMF at the natural frequency. The transfer function between input harmonic excitation and output structural response was obtained from the DMF, and the response reduction factor of the root mean square (RMS) of displacements with and without friction dampers was analytically determined. Using the proposed procedure the friction force required for satisfying a given target response reduction factor was obtained. The response reduction factors were obtained for the structures with different natural frequencies subjected to ten earthquake records. Based on the dynamic analysis results, it was concluded that the mean response reduction factors matched well with the target values.