Seismic performance assessment of non-code-conforming and code-conforming supporting structures of elevated tanks using conventional and risk-based decision models

Abstract

The seismic performance of the supporting structure of the replica of an elevated tank that collapsed during the Kocaeli earthquake and its variant designed according to Eurocode 8 provisions was investigated. First, the performance of the tank was verified for the Kocaeli ground motion. Results of non-linear seismic response history analysis using simplified models accounting for different tank filling levels showed that the simplified model could provide qualitatively the same damage as were observed during the earthquake, while the seismic performance of the code-conforming tank was satisfactory. Then, the seismic performance assessment of the non-code- and code-conforming tanks was further investigated using the conventional decision model, which accounts for the demand-to-capacity ratio given the seismic design action, the conditional risk-based decision model and the risk-based decision model which utilise, respectively, the probability of exceeding a designated limit state for a given design seismic action and for a given period. The seismic performance of the non-code-conforming elevated tank was found insufficient by any of the three decision models, which indicated the need for action towards risk reduction for such structures. The opposite was realised for the code-conforming tank. However, the conventional decision model may be misleading because it indicated that the structure might be considered overdesigned, while risk-based decision model showed that the seismic performance of the code-conforming tank was close to the target value, set to 1% in 50 years. In the future, risk-targeted design approaches can improve decision-making in the design of critical components of industrial facilities.