Oil Storage Tank Settlement Assessment Based on Standard and Finite Element Analyses

It is well known that foundation settlement of tank is particularly severe, and can produce distortion and stress of the tank, especially differential settlement around the circumference of the foundation below the shell of large-volume tank. The settlement standards involving European EEMUA 159-2003, American API 653-2009, and Chinese codes SH/T 3123-2001, SY/T 5921-2011 for in-service assessment of large-scale storage tank were reviewed and discussed. Finite element model for strength assessment of large-scale oil storage tank was developed based on actual field data of tank foundation settlement. The whole stress distributions and deformation of seven large-scale oil storage tanks in a depot in China were analyzed under the conditions of the practical pressure test through finite-element method. It also provides a comparison between an analytical model based on settlement criteria and a finite element model that replicates field operating loading and settlement conditions of storage tanks. A basis for comparison between models was established from the maximum allowable settlement and stress values. It was found that results from settlement standards of tank in China and other countries were more conservative than those from FEA, and SY/T 5921 in China made most stringent requirements for the tank settlement. The evaluation indicators of differential foundation settlement around the tank circumference are unreasonable in standards and rules mentioned above, the structural response of tank such as stress and deformation under foundation settlement should be considered sufficiently.