Buckling design of large circular steel silos subject to wind pressure

Abstract

Large steel silos are typical kinds of thin-walled structure which are widely used for storing huge quantities of granular solids in industry and agriculture. In the present analyses, buckling design of large steel silo subject to wind pressure is demonstrated in accordance with Eurocode (EN1990, 1991, 1993) and the proposed combinational Load Case WE (wind and empty silo) and WF (wind and full silo). The finite element model is established by using the commercial general purpose computer package ANSYS. Five types of buckling analyses are carried out for the geometrically perfect and imperfect models with and without the consideration of the material plasticity, which are designated as LBA, GNA, GMNA, GNIA, and GMNIA in EN 1993 Part 1–6. The geometrical imperfections are known to have a large impact on the buckling behavior of steel silo structure, in which the magnitude and distribution of the weld depression during construction process is adopted to account for fabrication quality. The buckling behavior of a reference silo with a diameter of 40m and an aspect ratio of 0.9 is first investigated, which shows that the buckling behaviors from Load Case WE and WF are much different. The material nonlinearity shows little influence on buckling resistance in Load Case WE, while the buckling resistance and buckling mode is much sensitive to weld imperfection. In Load Case WF, both material nonlinearity and geometrical nonlinearity effect is strong and detrimental to buckling behavior of steel silos, resulting in decrease of buckling resistance. The buckling deformation corresponding to the critical point in Load Case WE is governed by the circumferential compression which is generated in the windward region of the shells localized at the top part of silo wall. The buckling mode in Load Case WF takes the form of the well-known elephant-foot deformation at the bottom part of the shell wall, which is induced by the meridional compressive stress. It is also indicated from the parametric analyses that the buckling resistance of steel silo is closely correlative with the loading conditions involving the wind velocity, the patch load, and the geometrical parameters including the aspect ratio, the radius-to-thickness ratio, the type of wall thickness, and the wall openings.