Finite Element Analysis and Improved Evaluation of Mechanical Response in Large Oil Storage Tanks Subjected to Non-Uniform Foundation Settlement

This study developed a finite element model to address the issue of non-uniform settlement in large crude oil storage tanks. The model consisted of four key components: the tank foundation, bottom plate, wall plate, and large fillet welds. The Ramberg-Osgood model was used to describe the material’s nonlinearity. Key factors such as the radius-to-thickness ratio, height-to-diameter ratio, harmonic number, and amplitude were evaluated for their impact on the radial deformation of the tank’s top wall. Two numerical models were developed—one accounting for the coupling effect between the foundation and the tank bottom, and the other without it. The differences in radial deformation between these models were analyzed, revealing that deformation was minimally influenced by the radius-to-thickness ratio, but increased with higher height-to-diameter ratios and harmonic amplitudes. At low liquid levels, radial deformation increased with harmonic number, but at high levels, it decreased once the harmonic number exceeded four due to the decoupling of the tank bottom from the foundation. The model considering foundation coupling exhibited less radial deformation compared to the one neglecting it, particularly as the harmonic number and amplitude increased. An improved evaluation method identified a critical range of harmonic amplitudes for a 100,000 m3 tank, within which the coupling effect can be reasonably neglected, allowing deformation to be calculated using the simpler model.