Deformation Analysis Of In-Service Liquid Storage Tanks Under Differential Settlement Around The Tank Wall

Vertical cylindrical steel tanks are widely used to store gases, liquids and solids usually which consist of head cover, tank wall, floor and accessories. Most tanks are constructed in the coastal areas for the convenience of transportation and handling. Due to the weak bearing capacity of foundation, the tanks are susceptible to settlement deflections in varying degrees, in which the differential settlement around tank wall is the most detrimental to the tank. The paper studied the stress and deformation of in-service storage tanks based on the actual measurement of differential settlement with the method of finite element numerical simulation, proposed a new method to process the settlement data and analysed the influence of the different heights of liquid storage on the differential settlement deformation. The main studies are listed as follows:(1) The paper aimed at remedying the deficiencies of the differential settlement data processing methods, and proposed a new method to fit the differential settlement curve. Meanwhile, based on the actual settlement cases, the fitting effect which applied the new method to process the data is favorable.(2) The paper analysed the influence of the function form of differential settlement on the deformation of variable thickness steel tank, and calculated the stress based on the sinusoidal harmonic settlement function and cosine harmonic settlement function respectively then superposed linearly, and compared its result and the stress based on differential settlement function then calculated the relative error between them as well as the relative error of radial displacement. The study found that as the increase of amplitude of harmonic settlement, the relative error of stress and radial displacement increases simultaneously, as the increase of harmonic order, the relative error of radial displacement presents a tendency that increases at first then decreases, while the relative error of stress does not change distinctly.(3) The paper analysed the influence of the different heights of liquid storage on the differential settlement deformation, and calculated the stress and radial displacement of differential settled tank based on the different heights of liquid storage, and concluded the variation tendencies of Mises stress and radial displacement with the change of heights of liquid storage based on a calculation case of fixed roof tank and floating roof tank. The study found that as the decrease of height of liquid storage, Mises stress presents a tendency that decreases at first then remains unchanged. For the floating roof tank, the influence of height of liquid storage could be omitted, while for the fixed roof tank, the influence should only be taken into account when the height of liquid storage is high.(4) A buckling analysis method which used to analyze the buckling behavior of fixed roof tank and floating roof tank based on differential settlement applied for the differential settled tanks was proposed. The result indicated that with this method the computational expense can be reduced based on the differential settlement load is fully loaded and offer valuable references for the buckling analysis of storage tanks.