The aim is to improve the current shape limitation requirements of BS 5400: Part 3, which are known to be especially conservative for bulb flat stiffeners. There are many existing bridges with bulb flat stiffeners that do not conform to the current Code. This paper presents a practical method for finding the local critical stress for plate /stiffener combinations, without limitations on section slenderness. The critical component is identified for all possible buckling wavelengths, which can vary
between the length of the stiffened plate and the wavelength of an encastré plate or stiffener, depending on the section geometry. For each possible wavelength, the critical stress of the critical component is found, when restrained by the other component, using an iterative method that is easily programed for a desktop computer.
Validation is provided by 60 finite element (FE) solutions. The results will be incorporated in a method for design or assessment.
S.K.G. Chou and J.C. Chapman