Buckling-Restrained Braces (BRB) Seismic Design - A Consulting Engineer’s Consideration

Abstract

There is no standard for the design of Buckling-Restrained Braces (BRBs) frames in New Zealand. Consequently, a consulting engineer would need to consider a range of overseas design standards and latest research findings and incorporate into a New Zealand code-compliance framework. This “Alternative Solution” pathway to satisfy the New Zealand Building Code means peer review and agreement with peer review is required. This paper describes the design journey and technical challenges the authors had in the seismic design of the BRB for the New Zealand International Convention Centre (NZICC). BRB frames are used as the primary ductile lateral load bracing system, acting in parallel with the moment-resisting frames formed by the primary cruciform columns and storey-deep trusses. Due to the vertical irregularity and a dual-system structure, a direct displacement-based design (DDBD) approach was used in parallel with a more convention code-compliant force-based design, to derive the BRB design actions. The design of the BRB connections, in particular the gusset design is particularly challenging due to the diverging views and numerous methodologies available. We have considered several analytical methods for the BRB connection design and commissioned two full-scale testing of the critical BRB and the gusset connection. Lessons learnt