Influence of non-linear behavior on seismic response parameters

This paper deals with the effects of post-yielding stiffness on the response of non-linear structural systems under seismic actions. In detail, two hysteretic models are considered: a bilinear plastic model, representing structures that exhibit strain hardening characteristics, and an elastic-perfectly-plastic model, widely adopted in design codes. For these models, a parametrical study is carried out to assess the influence of post-yielding stiffness ratio on some non-linear response quantities, such as the response modification factor, the ductility demand and the damage index. The analysis is developed on a SDOF system subject to El Centro earthquake and demonstrates that the elastic-plastic constitutive law is excessively conservative to evaluate structural deformations. Finally the study provides useful information also from an energetic point of view.