Collapse behaviour of stiffened plating under thrust. (1st report)

A series of elastoplastic large deflection analyses of stiffened plates under thrust is performed using nonlinear finite element method, and the influence of cross-sectional geometries of stiffeners on the buckling/plastic collapse behaviour of stiffened plates is discussed. Interactions between stiffener and plate element are considered by modeling both the components with shell finite elements. It has been found that: (1) Local buckling strength between stiffeners, inplane rigidity after the local buckling and ultimate strength are significantly increased by a flexural-torsional rigidity of stiffeners. (2) Elastoplastic secondary buckling takes place after initial local buckling for all the stiffened plates considered here. (3) Larger ultimate strength can be attained by stiffeners with web of smaller depth-to-thickness ratio. However, a load-carrying capacity after the ultimate strength tends to decrease more rapidly, because of the formation of overall buckling collapse mode. (4) Stiffeners with web of larger depth-to-thickness ratio are likely to collapse in local torsional mode, resulting in a lower ultimate strength. However, the decrease of load-carrying capacity after the ultimate strength is not rapid, because of a wide spread of collapsed region over the plate.