A cyclic viscoplastic damage model with application to seismic response of metallic plate dampers

This study is connected with inelastic behavior of metallic dampers, which represent one class of effective passive energy dissipation devices used to protect structures during strong earthquake excitations. The main objectives of this study are to understand analytically the inelastic behavior of metallic dampers considering time dependent material response, thermal effects, damage mechanisms, and ratchetting phenomena. An additional objective is to develop several new constitutive models for cyclic response of metals with much broader applicability.;This study is divided into three parts. First, a two surface plasticity damage model considering thermal effects and material degradation processes was formulated by combining concepts from a cyclic plasticity model and damage mechanics. The resulting model was validated by comparing with experimental data for metallic dampers. In the second part, the two surface plasticity model and several other existing cyclic plasticity models are used to simulate the uniaxial ratchetting response of CS 1020 and CS 1026 steel. In the third part, a rate dependent two surface model was formulated based on a unified viscoplastic formulation, and then finally was verified by comparing with experimental results.;Finally, this work concludes that these considerations help to understand the inelastic behavior of metallic dampers under earthquake loading and to develop effective designs for either new or retrofitted structures with metallic dissipation devices. The constitutive models developed here should also be useful for a wide range of metals and applications.