Nonlinear numerical evaluation of large open-top aboveground steel welded liquid storage tanks excited by seismic loads

A numerical study is conducted using finite element models of large, circular, cylindrical, aboveground, steel, open-top, liquid storage tanks subjected to horizontal seismic forces. Nonlinearities of both material properties and geometry deformations are included. Soil-structure interactions are implemented into the finite element models by using a series of elastic springs representing a stiff soil foundation. Hydrodynamic hoop stresses, elephant's foot buckling, and uplift are measured for tanks with height to radius ratios, or aspect ratios, between 0.4 and 2.0. The finite element models are compared to the provisions of API 650 Annex E, with special attention to the anchorage ratio, J. The results show that, while the finite element models are much more complex than the theoretical and empirical equations provided in API 650, the total hoop and axial compressive stresses are comparable. Furthermore, the anchorage ratio limits set by API 650 seem to be in good agreement with the finite element models in terms of uplifting behavior.