Demands on nonstructural components in buildings with controlled rocking braced frames

Abstract

Controlled Rocking Braced Frames (CRBFs) have been developed as a high-performance seismic force resisting system that can self-centre after an earthquake and avoid structural damage. A CRBF is designed to uplift and rock on its foundation, and this response is controlled using prestressing and energy dissipation devices that are engaged by uplift. Although CRBFs have been shown to have desirable structural performance, a comprehensive assessment of this system must also consider the performance of nonstructural components, which have a significant impact on the safety and economic viability of the system. The purpose of this paper is to evaluate the demands on nonstructural components in buildings with CRBFs in comparison to demands in a reference codified system, taken here as a buckling restrained braced frame (BRBF), as well as to identify which design parameters influence these demands. The responses of various types of nonstructural components, including anchored components, stocky unanchored components that slide, and slender unanchored components that rock, are determined using a cascading analysis approach, where absolute floor accelerations generated from nonlinear time-history analyses of each system are used as input for computing the responses of nonstructural components. The results show that the downside of maintaining elastic behaviour of the CRBF members is, in general, larger demands on nonstructural components compared to the BRBF system. These demands are not highly influenced by impact during rocking or by the supplemental energy dissipation provided, as the vibration of the CRBF in its higher modes is primarily responsible for the higher demands.