Optimal Nonlinear Damping for Inelastic Structures Using Dimensional Analysis

Supplemental energy dissipation in the form of nonlinear viscous dampers is often used to improve the performance of new structures or to retrofit the existing ones. The optimal amount of nonlinear damping is needed to achieve the desired performance of inelastic structures. Using dimensional analysis, this paper proposes a dimensionless nonlinear damping ratio that decisively quantifies its effects on responses (e.g. drift and total acceleration) of inelastic structures subject to pulse-type near-fault ground motions. It is demonstrated that the added nonlinear damping is not always beneficial for inelastic structures, resulting in the increase of their total accelerations under certain ground motions. A critical structure-to-pulse frequency ratio exists, under which an optimal nonlinear damping needs to balance between the increases of total acceleration and the reductions of the structural drift.