Steady-State Response of Yielding Shear Structure

An approximate analytic technique is used to investigate the steady-state response of a continuous shear beam including both yielding and viscous dissipation. The yield model is one which gives a general class of systems having continuously rounded hysteresis loops. Two different effective damping parameters are defined for such a system; one based on observations of peak resopnse and the other based on bandwidth measurements. It is shown that the effective damping in each mode of the yielding system is strongly dependent on the excitation amplitude, and that the two different damping definitions can give results which differ by as much as 40%. The effective damping in the lowest several modes of the system may either decrease, remain nearly constant, or increase with increasing mode number depending on the parameters describing the system and the level of excitation.