Design of Anchorage for Flexible Structures

The analytical calculation of hold-down loads for open-top tanks and other flexible structures relies on a fundamental assumption that the structure behaves rigidly. Consequently, the relevant design codes provide measures to achieve sufficient rigidity in order to validate this assumption. This paper examines the open-top tanks meeting recognised codes such as API650 [1], and AWWA D100 [2] and the actual hold-down loads through finite element analysis. The results show that the assumption that the tanks are rigid is not necessarily conservative and that higher than expected localised hold-down loads may arise for a given set of geometries. The paper considers possible changes to the ring stiffeners recommended by the design codes and the approach employed by other codes in the design of flexible shell structures.