Derivation of Fragility Functions for Steel Storage Tanks Using Far- and Near-Field Record Sets

Liquid-storage tanks are among industrial plants’ most important and critical elements, particularly during a seismic event. The leakage of the content could lead to substantial economic losses, disruption of the plants and, no less importantly, environmental pollution. Therefore, an accurate design and assessment of their performance is crucial in reducing the risk of catastrophes. Yet, past earthquake events have shown the need for a more reliable comprehension of tanks’ seismic behaviour. To fulfil this scope, it is necessary achieving a clear understanding of the seismic input selection, and the optimal ground motion sets to excite the storage tanks properly. This paper aims to study the seismic behaviour of a wide taxonomy of storage tanks with different sets of records, considering both far-field and near-field earthquakes. The tanks were developed considering several geometric dimensions, including the diameter-height ratio, the wall thickness, the liquid height and tank radius. The tanks were assumed to be located in three Italian sites, representative of low, medium and high seismic zones. Nonlinear time-history analyses were performed to derive fragility curves and assess the tanks’ seismic performance, taking advantage of suitable limit states. The results of this study demonstrate the significant impact of choice between far-and near-field record sets on the seismic performance of the tanks, particularly when considering the fragility curves dispersion. Furthermore, the fragility curves derived from the analyses can be a valuable tool for conducting risk scenario assessments for government bodies and stakeholders, thereby enhancing the safety and resilience of industrial plants.