PERFORMANCE ASSESSMENT OF PINNED ROCKING CORE WALLS IN STEEL MULTI-STORY BUILDINGS SUBJECTED TO STRONG SEISMIC GROUND MOTIONS

Abstract

It is known that design guidelines within current building codes can ensure adequate safety levels against severe seismic events by promoting energy dissipation through large inelastic deformations and residual drifts. Nevertheless, this ductility-based design philosophy often results in extensive reparations that are neither financially sustainable, nor able to secure the post-earthquake serviceability of the structure. Hence, several strategies have been proposed so far to mitigate potential structural and nonstructural damage in multi-story buildings under strong seismic events. Particularly, the low-damage philosophy is based on the design of high-performing, cost-effective structural systems that can withstand large seismic ground motion intensities with minimal damage and low socio-economic losses. This design methodology leverages on the installation of innovative damage mitigation technologies to improve the seismic performance of structural and nonstructural elements, and it is suitable for the design of new constructions as well as for the retrofitting of existing buildings. Within this framework, the present study investigates the behavior of an inner braced rocking core as a low-damage design solution for mitigating the seismic risk of a multi-story steel frame. The pinned rocking wall system is simulated by including viscous dampers mounted between the column bases and the foundation, whereas its self-centering capabilities basically rely on the self-weight of the structure. Nonlinear models with both fixed- and rocking-base core wall conditions subjected to a large set of seismic ground motion records are analyzed in order to properly appraise the potential benefits of the rocking structure on the seismic performance of the building.