For economic reasons, foundations of steel storage tanks tend to be shallow and suffer as a result of potential differential settlements under load. On the other hand, steel tanks tend to be flexible and ductile, and are able to tolerate a limited settlement without distress. To have a reasonable limitation for settlement, the tank structure should be analysed in a rational manner. The effects of peripheral differential settlement on the storage tank shell structures are evaluated for the practical case of tapering wall thickness in floating roof tanks which have a relatively flexible response to warping displacements. Previous research has centred on walls of uniform thickness, and is therefore of limited relevance. Settlements of various form are imposed at the base of the tank and resulting deformations and stresses determined in accurate finite element analysis. The significance of the stresses in the primary wind girder and adjoining shell has been taken into account by relating the top radial displacement of tank to its bottom settlement. Results of recent tests of shell behaviour under bottom displacement, focussing on stresses on the wind girder, are reported.
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