Abstract: The FEA method was used to build a full size model of large oil storage tank. Influences of foundation settlement on elephant foot buckling critical load of a large-scale, unanchored and external floating roof tank were analyzed in order to optimize the seismic design. Various items of tanks geometry including tank foundation, unanchored bottom with slope, tapered shell thickness, wind girders, stiffening rings, other attachments and appurtenances were taken into account thoroughly in the non-symmetrical full finite element model. On the basis of Fourier transform, foundation settlement was simulated by several combinations of harmonic waves. The radial deformation, buckling deformation mode and buckling strength were researched before and after foundation settlement. The influences of different orders of harmonic waves, harmonic wave amplitudes, trough and crest on elephant foot buckling critical load of tank were proved up while single harmonic settlement happened. The results show that foundation harmonic settlement has a negative influence on elephant foot buckling critical load, that the critical compressive stress of elephant foot buckling of tank shell decrease with the increasing harmonic amplitude of foundation settlement, and that the resistance capacity reduces as the harmonic order number rises under the same settlement.

Key words: tanks, foundation settlement, harmonic wave, finite element analysis(FEA), elephant foot buckling