Thin-Walled Struct. 26, 261-286, 1996


DETERMINATION OF EFFECTIVE BREADTH
AND EFFECTIVE WIDTH OF STIFFENED PLATES
BY FINITE STRIP ANALYSES

X. Wang and F.G. Rammerstorfer

Institute of Lightweight Structures and Aerospace Engineering,
TU Wien, Vienna, Austria


Abstract - A finite strip (FS) method is presented for the numerical investigation of two design parameters - effective breadth and effective width - of stiffened plates. For the effective breadth, stiffened plates under bending are studied. Due to the transverse bending loads there is shear transmission through the plate form the stiffener which leads to a non-uniform longitudinal stress distribution across the plate width. This phenomenon, termed as shear lag, can be represented by the 'effective breadth concept', and has been extensively studied by analytical methods. A linear FS method is presented which utilizes the advantages of decoupling of Fourier terms on the one hand and, on the other hand, allows the treatment of both webs and flanges using a plate model. A definitely different situation exists for estimating the effectiveness of the breadth (or width) of plates in the postbuckling range. The 'concept of effective width' is based on the fact that plates with supported longitudinal edges and/or stiffeners can accept additional load after buckling under longitudinal compression, and enables the designer to evaluate the postbuckling strength of plate structures simply by using the design parameter 'effective width'. Several formulae (most of them empirically derived) exist for an approximative calculation of the load dependent value of the effective width. A nonlinear FS method is developed and applied to the investigation of the postcritical strength of locally buckled structures. An incremental successive iterative procedure is introduced for an effective numerical analysis.


(hjb,961031)