On the Applicability of Conventional Seismic Design Methodologies to Hybrid RC-Steel Systems

This paper addresses the application of conventional (force-based) seismic design methodologies to hybrid RC-steel systems. The q-factor-based EC8-3 seismic assessment procedure is first reviewed. A case-study application follows, analyzing and discussing the difficulties a practitioner will face when assessing the efficiency of a steel-brace retrofitting system designed within the framework of EC8-1. Afterward, the performance of the obtained retrofitted structure is evaluated using nonlinear analysis. The obtained results are discussed in light of the EC8-3 performance requirements, and conclusions are drawn about the adequacy of the force-based design (FBD) methodology (and associated q-factors) for such situations. The study shows that the process does not ensure the adequate seismic behavior of the retrofitted structures. It thus calls for the development of an effective performance-based design methodology that explicitly considers the interaction between the two structural systems (RC structure and steel braces), namely the influence of the steel braces’ resistance on the deformation capacity of RC members.