Abstract:

ESDU 03013 introduces a Fortran 77 program (ESDUpac A0313). The program calculates efficient flange and web thicknesses for a composite I-section beam to withstand up to 10 user-specified combinations of bending moment and shear force. The section is treated as thin-walled so that the flange and web thicknesses are small compared with the overall dimensions of the section, that is its depth and width; those dimensions are prescribed by the user who also provides a minimum value of the overall flexural rigidity of the beam. The laminates that make up the beam are all of the same unidirectional composite plies layed up in O and/or + 45 and -45 layers. The connection between the web and flanges is made by continuing the web layers around to the inner faces of the flanges. In the first estimate of the thicknesses, it is assumed that the applied bending moment is reacted entirely by the layers in equal thickness flanges and that the shear force is taken entirely by the web. That provides a starting geometry to which a more precise design procedure is then applied. In that procedure, various heuristic design rules are employed, using calculated values of reserve factors relating to strains across the section, flange and web buckling, and flexural rigidity. The procedure is iterative and is completed when all reserve factors lie between 0.99 and 1.05 inclusive.