Equivalent Viscous Damping for Yielding Structures

The paper treats the application of the concept of equivalent viscous damping to the steady-state response of simple yielding structures subjected to sinusoidal excitation. Using the elasto-plastic oscillator as an example, it is shown that results differing by several hundred per cent can be obtained, depending on the way that the resonant frequency shift characteristic of yielding response is modeled. It is concluded that the results of simple amplitude matching produce the most useful equivalent damping for most purposes, and it is shown that this approach is meaningful also for earthquake response. When applied to the elasto-plastic oscillator, this technique gives a maximum value of 15.9% equivalent damping for steady-state response to sinusoidal excitation.