Earthquake-induced nonlinear sloshing response of above-ground steel tanks with damped or undamped floating roof

Liquid storage tanks are widely used in the industry and can contain not only harmless substances but also various ones that can be explosive and toxic or pollutant, thus implying that both the structure and the content must remain safe and operational under different types of loading. The same applies to any tank-connected plant system/item. Yet, past earthquakes repeatedly demonstrated that even if structural damage is prevented in the shell, severe occurrences may still be observed due to sloshing phenomena, which drive the tank-fluid system response with high impacts in case of accidental release of chemicals. Therefore, this paper studies an energy dissipation system consisting of floating roof and external dampers that are utilized to control liquid vibration by augmenting the level of damping. In order to evaluate its effectiveness at the design-level earthquakes, a series of explicit nonlinear dynamic analyses have been performed, and comparisons are provided between floating roofed steel cylindrical tanks equipped with supplemental devices and counterparts without them. Changes in seismic performance because of geometrical variations in the tank (i.e. aspect ratio) and seismic input (i.e. far and near field earthquakes) have been quantified by means of experimentally validated numerical models that account for material and geometrical nonlinearities, as well as for fluid-structure interaction in an explicit manner. Shake-table tests available in the literature have been simulated, and the proposed modelling criteria show a good fit with experimental data on two tank specimens. Analysis data sets involving three tank geometries reveal that even if the dissipation system targets mainly large-capacity tanks, it can be effectively used to enhance the performance of any system, reducing the sloshing wave height which can be excessive especially when the tank is subjected to severe near field ground motions.

Automated summary

This study investigates an energy dissipation system consisting of a floating roof and external dampers to control liquid vibration by increasing damping levels. Numerical simulations and seismic tests show that this dissipation system can reduce sloshing wave height in tanks during earthquakes, improving overall system performance.