Analysis of Some Double Layer Grids

An approximate method of analysis based upon the replacement of planar trussed members by analogous prismatic I-beams in double layer diagonal grids is examined. The goemetrical properties of the analogous I-beams are, in each case, derived from those of the planar trussed members. The results of an approximate analysis, in which the analogous I-beams are considered to have both flexural and shear rigidity, but no torsional rigidity, are compared with those of an analysis in which the planar trussed members are considered to be constructed from an assembly of members, having axial rigidity only. It is shown that the approximate analysis in most cases is reasonably accurate and that consideration of shear rigidity consistently leads to an improvement in the results.