A New Design Method for Longitudinally Stiffened Plates

Longitudinally stiffened steel plates are becoming increasingly important in bridge design as the size and span of new bridges increases. This paper presents a new method for the design of longitudinally stiffened plates, with or without transverse stiffeners. The method considers explicitly the three effects of plate bending, plate torsion and flexural buckling from the member buckling curve. It combines these contributions to give the buckling resistance of the stiffened plate including the long yield plateau arising from plate behaviour. Explicit consideration and combination of the three effects enables the designer to optimise a structure because the relative importance of each effect is clear. Also, the buckling length of the stiffeners is found by the method so the mode shape is clear to the designer and the spacing of diaphragms can be optimised. The method is suitable for use with effective widths to allow for plate slenderness. The method avoids a limitation of AASHTO LRFD which recognises only the specified minimum stiffness of longitudinal stiffeners when designing plates stiffened longitudinally and transversely. The method of combination of the three effects avoids the anomalies that occur for certain geometries in Eurocode 3 Part 1.5 which uses an interpolation between the buckling curve for unstiffened plates and a buckling curve for compression members. The method involves no iterations and is suitable for application in a design office by spreadsheet or pencil and paper calculations.

View content