Life-cycle Cost Assessment of RC Frames Using Multi-level Performance-based Structural Optimisation

Abstract

Abstract Most conventional seismic design approaches aim to provide solutions with sufficient strength to primarily ensure “life safety”, but cannot directly limit structural damage under different hazard levels. They generally lack provisions for determining whether structural configurations can be improved to achieve greater cost efficiency. This study adopts life-cycle cost analysis as an assessment tool to investigate economic efficiency of RC frames that are designed using a performance-based optimisation method centred on the concept of Uniform Damage Distribution (UDD). In optimisation approach, both local (i.e. plastic hinge rotation) and global (i.e. inter-storey drift) structural responses are controlled to closely approach the target limits at multiple performance levels, minimising building’s initial construction cost. To evaluate total life-cycle costs, the expected structural damage losses due to future earthquakes are calculated in a probabilistic manner. The total life-cycle costs are determined for optimised and code-based 3-, 5-, 10- and 15-storey RC frames. The results highlight that, compared to the Eurocode-based frames, optimum design solutions: (i) reduce initial costs by up to 15%, (ii) achieve up to 64% savings in total life-cycle costs, and (iii) result up to 85% less global structural damage under a wide range of earthquake intensities. Based on sensitivity analysis on the selection of different earthquake records, it is recommended to adopt a group of spectrum-compatible artificial earthquakes for the optimisation process rather than natural records. The proposed optimisation can lead to considerable savings not only in initial costs, but also in expected total life-cycle costs of RC frames.