Abstract:

ESDU 98016 introduces Fortran programs (ESDUpacs A9816 and B9816, provided in compiled form) for calculating the initial buckling (local, flexural, torsional or torsional-flexural) loads for flat rectangular panels and struts using the finite strip method, a more general variant of the method used in, for example, ESDU 94005 and Struct 02.01.28. When applied to periodic displacement conditions like buckling, this method provides more rapid solutions than finite element analysis. Predefined skin-stringer sections are provided which relieve the user of having to generate the usually large finite strip model data file but, if required, arbitrary cross-sections may be defined by the user or, alternatively the file for one of the predefined sections may be adapted. The predefined stringer sections are beaded or unbeaded T, I, lipped J, machined or rolled-sheet lipped Z, machined unlipped Z and machined or rolled-sheet top-hat. For the rolled-sheet sections the corner radius is modelled. A special single-stringer panel model is included to represent a panel with many stringers. It uses predefined edge conditions in conjunction with the predefined sections and allows rapid exploration of the effect of changes in geometrical and physical parameter values. Adhesive layer and rivet elements are included to enable the stringer/skin joint to be modelled in a more realistic way, but inter-rivet buckling is not considered. Up to 10 different materials may be used in the models, although rolled-sheet sections are assumed to be formed of one material. The number of stringers is restricted to between 10 and 18 depending on the type of stringer but those values may be increased at a cost in computation time. Edge conditions are modelled by adding or removing nodal degrees of freedom. There are three analysis options: the load associated with a buckled half-wavelength equal to the simply-supported panel length, a complete curve of load against buckled half-wavelength, or a specific minimum buckling load from the curve. The construction of the input to the programs and the format of the output are explained and illustrated with worked examples. Warning messages are explained. A comparison is made of results obtained with the programs and data in other ESDU documents. ESDUpac A9816 is provided in a form that prompts on-screen for input data.