Performance based seismic design for Tall Buildings in Hong Kong

Abstract

This paper formulates an appropriate seismic design approach for tall buildings in Hong Kong. Particular care is given for local consideration of Hong Kong and a unique proposal is put forward. A single 2475-year return period hazard level is fostered as the performance goal, followed by a site specific design spectrum. Cracked stiffness is suggested for softer damaged concrete behaviour, implicitly considering material non-linearity in a pseudo inelastic response spectrum analysis. Material expected strength and unity value of material safety factor are proposed to avoid over-conservatism considering non-collapse performance state. The capacity design philosophy is incorporated with identification of force-controlled and deformation-controlled actions on members, allowing over-strength factor to elevate the demand on force-controlled members. Simplified global (drift) and local component (strength) acceptance criteria are suggested with associated procedures and limit. Also, a typical 41-story reinforced concrete building in Hong Kong is used as an example to further demonstrate the proposed Performance Based Seismic Design (PBSD) approach. The outcome of the analysis and design is well within the acceptable range, with minimal additional cost penalty imposed on the building. The proposed PBSD approach is superior for low-to-moderate seismicity region with no earthquake design consideration in the past but filled with abundance of “prescriptive code-exceeding” building.