Seismic design of steel moment-resisting structures based on life-cycle cost

Abstract

The design of structures based on a design earthquake mainly addresses the direct cost incurred during the construction phase, while the lifetime cost of the structure is often ignored. An investigation was performed on three steel moment-resisting structures of four storeys (case 1), seven storeys (case 2) and ten storeys (case 3) and their life-cycle costs (LCCs) were determined based on different earthquake loads. Each of the structures was designed 14 times: one model for a design earthquake, five models for higher earthquake loads and eight models for lower earthquake loads. The results revealed that none of the structures designed based on the design earthquake provided a minimum LCC. In cases 1 to 3, the LCCs were minimised when a 60%, 50% 40% increase was applied to the design earthquake, respectively. The aim of this work is not to criticise current seismic codes with respect to life safety during an earthquake, but to provoke different parts of engineering communities to think about how an LCC-based design can change costs imposed on their clients, be this the cost of repair and relocation or the cost of injuries and disabilities. The proposed methodology can be used as a case-independent tool for different structures.