Effect of viscoelastic dampers on hysteretic response of reinforced concrete elements

Abstract

This paper presents the effect of viscoelastic (VE-) dampers on hysteretic response, ductility and energy dissipation of reinforced concrete elements. A parametric study is carried out on reinforced concrete (RC) elements of different design ductilities (strength levels) having different degradation and pinching characteristics. The study uses the fiber element of the DRAIN-2DX program to simulate stiffness degradation, strength decay and pinching effects of the reinforced concrete elements. The VE-damper behavior is simulated by using the writer's nonlinear element based on the fractional derivative approach. The element is made compatible with the nonlinear dynamic analysis program DRAIN-2DX. The study indicates that VE-dampers significantly decrease the curvature demand at the plastic hinges, thus reducing the effect of stiffness degradation, strength decay and pinching on the reinforced concrete element hysteresis. The energies dissipated through hysteresis of the reinforced concrete element and the VE-damper element are studied under increasing amounts of added VE-damping ratios of the systems. Systems having different periods, and designed for different ductility ratios (strength levels), are considered. Increase in the VE-damping ratio of the systems progressively reduces the energy dissipation demand on the reinforced concrete elements. The contribution of energy dissipation by the VE-damper, however, increases at the same time. The net effect, more often, is an overall and significant increase in the total energy dissipation of the system. The degradation characteristics of the RC element hinges do not seem to affect the energy dissipation capability of the system with the VE-damper. The study indicates that the magnitude of energy dissipation by the VE-damper increases with the increase in added VE-damping ratio, up to a certain point beyond which further increase in VE-damping is not beneficial. This limit on the VE-damping ratio seems to depend upon the period of the system, but may be rather independent of its design ductility (strength level). The study also indicates that a particular value of VE-damping ratio, which is typically less than the above indicated limit, and requires some inelastic behavior of the RC elements, would maximize the total energy dissipation of the system. This optimum VE-damping ratio seems to depend upon the period and the design ductility ratio (strength level) of the system.