Assessment of different failure modes in liquid storage tanks under horizontal ground motion

Steel storage tanks are generally vulnerable to dynamic failure under strong ground motion. The reason for that is partly because of small thickness of tank walls which contribute to either elastic buckling or inelastic post-buckling mechanisms. The tank aspect ratio plays a pivotal role in developing different failure modes. In order to investigate different failure mechanisms, case study tanks considering different aspect ratios that are fully anchored at the base are introduced. Dynamic fluid-structure interaction is utilised based on so-called added-mass method and tank walls are modelled using general purpose finite element platform to detect potential failure modes. Seven strong ground motions are selected from NGA database and spectrally matched with target spectrum. Incremental dynamic analyses are conducted to identify critical failure modes and construct fragility curves. The results demonstrate that changing tank aspect ratio contributes to different modes of failure ranging from elephant foot and diamond shape to secondary buckling modes.