Hysteretic behavior of viscoelastic dampers subjected to damage during seismic loading

Abstract

The design, beyond-design, and residual performance of full-scale viscoelastic (VE) dampers has been previously investigated with sinusoidal reversal loading experiments. Fractional derivative models that can individually describe the hysteretic behavior of VE dampers at different performance stages have also been proposed. However, the performance of VE dampers when subjected to damage or after suffering damage under transient responses due to seismic loading, rather than steady responses due to harmonic loading, has not been experimentally analyzed. In this study, a full-scale VE damper is tested with seismic responses obtained by numerically analyzing a viscoelastically damped structure. The seismic loading test results show that the VE damper can remain intact and exhibit the design performance before being subjected to a shear strain of approximately 700%, which is larger than the result (approximately 600%) observed previously from the harmonic loading tests on two geometrically and mechanically identical dampers. Before the VE damper suffers damage, its experimental seismic responses are compared with predictions to verify the accuracy of the fractional derivative model at the design performance stage. By considering appropriate switch rules for different fractional derivative models, the experimental seismic responses of the VE damper when subjected to damage, as well as after it suffers damage, during seismic loading can be reproduced satisfactorily. The numerical results for the viscoelastic stick model are discussed, and the pre- and post-damage performance of the installed VE dampers is characterized using the design, beyond-design, and residual fractional derivative models as well as the proposed switch rules.