Tsunami fragility for anchored floating-roof atmospheric tanks

One of the issues for quantitative risk assessment in the process industry, is incorporating so-called NaTech risk, that is considering the potential consequences of natural hazards, whose impact on facilities can cause accidents such as explosions, fires, or toxic substance release. In this context, this paper explores the behaviour of anchored atmospheric storage tanks under tsunami, with the goal of quantifying their vulnerability via parametric fragility functions. Three archetype tanks with different aspect ratios were considered, while tsunami vulnerability was evaluated for different filling levels. The effects of tsunami-induced pressure on the tanks were calculated numerically following an equivalent-static approach, based on nonlinear analyses of finite element models. Each tank was subjected to various combinations of tsunami inundation levels and increasing flow velocities, obtaining structural response of each tank's steel shell and anchorage system. Parametric tsunami fragility curves were obtained, also with the aid of a site-specific conditional tsunami hazard model, surrogating vector-valued hazard analysis. It was found that the predominant failure mode depends on the aspect ratio and filling level, with emptier tanks being more vulnerable overall. The fragilities were then used to quantify the risk associated with loss of content due to structural failure, and the results were also compared those from existing models.