Structural damping estimation using a simple equation based on the equivalent viscous damping concept

Earlier research papers by the authors have presented a simple equation, derived using the equivalent viscous damping concept, to characterize the amplitude-dependency of modal damping. While initially intended for damping estimation on account of stick-slip surfaces acting on main structural systems of buildings within the linear range, the current paper discusses how this same equation can be used to describe damping in general given the force-displacement relationship of the element or structure of interest. This is done by modifying and extending the original derived equation to allow the calculation of amplitude-dependent damping given the force-deformation characteristic of the particular element or structure. The paper then presents amplitude-dependent damping estimates for a structure with a given modal pushover (i.e. force-displacement) curve generated by static nonlinear analysis as an example application of this simple formula. The effect of the resolution of the force-displacement curve on the damping estimate is discussed by contrasting the initial estimate against simplified force-displacement curves. Limitations and applications of this procedure in wind and seismic design are briefly discussed.