| Abstract: | Anchor forces with short cylindrical shells. Thin walled short cantilever cylinders, such as supply‐air‐chimneys, silos or tanks, develop a shell‐type distribution of membrane forces when subjected to natural wind. A structural analysis by hand involves a Fourier decomposition of the circumferential wind pressure distribution and a separate calculation for each harmonic, using an appropriate shell theory. With this classical method simple boundary conditions at the bottom edge of the shell, such as ‘pinned’ or ‘clamped’, can be modelled only. The use of a finite element code – if available – gives possibility to account for more realistic conditions at the bottom of the structure, such as elastic flanges and anchors or unilateral contact. In designing silos, tanks or chimneys however, as often encountered by the authors, structural engineers use beam theory to determine stress resultants and anchor forces, may this be due to lack of time or due to ignorance. Those who determine ‘real’ anchor forces obtain dimensions, which they feel to be inadequate and which are so much in excess of beam‐theory‐anchors that there should be much more failures with ‘beam‐designed‐anchors’. In the present paper some evidence on this apparent contradiction is given and a practical design approach is suggested. |
