Direct loss-based seismic design of reinforced concrete frame and wall structures

This paper presents a procedure to design reinforced concrete (RC) buildings to achieve an acceptable target level of earthquake-induced loss (e.g., deaths, dollars, downtime) under a site-specific hazard profile. The procedure is called "direct" since the target loss level is specified at the first step of the process, and virtually no iteration is required. The procedure is based on a simplified loss assessment involving a surrogate model for the seismic demand (i.e., probability distribution of peak horizontal deformation given ground-motion intensity) and simplified loss models for direct and indirect losses. For an arbitrarily-selected target loss level and structural geometry, the procedure provides the force-displacement curve of the corresponding equivalent single degree of freedom system. The principles of displacement-based design are adopted to provide member detailings (beams, columns, walls) consistent with such force-displacement curve. The procedure is applied to 16 realistic RC case studies with a lateral resisting system composed of frames in one direction and cantilever walls in the perpendicular one. They show different geometries, hazard profiles, and target values of direct economic expected annual loss. A benchmark loss estimation is obtained using cloud-based non-linear time-history analyses of multi-degree of freedom models. The procedure is conservative since the benchmark loss levels are always smaller than the targets. Such discrepancy is within 10% for 12 out of 32 case studies, between 10% and 20% for 13, between 20% and 31% for the remaining six. Therefore, the proposed procedure is deemed dependable for preliminary design.