The shape of circumferential weld-induced imperfections in thin-walled steel silos and tanks

The strength of thin-walled cylindrical shell structures is highly dependen t on the nature and magnitude of imperfections. Most importantly, circumfer ential imperfections have been reported to have an especially detrimental e ffect on the buckling resistance of these shells under axial load. Due to t he manufacturing techniques commonly used during the erection of steel silo s and tanks, specific types of imperfections are introduced into these stru ctures, among them circumferential weld-induced imperfections between strak es of steel plates. The shape of such a localised circumferential imperfect ion has been shown to have a great influence on the degree of strength loss of thin-walled cylindrical shell structures. The results of a survey of im perfections in an existing silo at a location in Port Kembla, Australia in combination with linear elastic shell bending theory was used to develop an d calibrate a shape function which accurately describes the geometric featu res of circumferential weld imperfections. The proposed shape function is t he first function to combine shell theory with actual field imperfection me asurements. It is a continuous function and incorporates all the necessary features to represent the geometry of a circumferential weld-induced imperf ection. It was found that after filtering out the effects of overall imperf ections three parameters governed the shape of the surveyed imperfections: the depth, the wavelength and the roundness. (C) 2001 Published by Elsevier Science Ltd.