Amplitude Dependency of Damping in Buildings

This paper first discusses the amplitude dependency of damping ratio. It is emphasized that there is no evidence of increasing damping ratio in the very high amplitude range within the elastic range of main frames, unless there is damage to secondary members or architectural finishing. The damping ratio rather decreases with amplitude from a certain tip drift ratio defined as "critical tip drift ratio". Next, the feasibility and efficiency of two simple and user-friendly but accurate damping estimation techniques are discussed: the Frequency Domain Decomposition technique; and the Multi-mode Random Decrement technique. Some full-scale examples demonstrating the damping estimation efficiency of both techniques are also shown.