The Bending of Pretwisted Thin-Walled Beams of Symmetric Star-Shaped Cross Sections
Abstract The customary method of determining the elastic bending deflections of pretwisted beams predicts that the deflections of a uniform beam with a cross section having equal principal moments of inertia will be independent of pretwist. Experimental deflections of a thin-walled pretwisted beam with a doubly symmetric cruciform cross section have been found, however, to be significantly larger than those thus predicted. Based on energy methods, an approximate analysis is developed for pretwisted thin-walled beams having symmetric star-shaped cross sections, which takes into account the effect of interactions between pretwist and distortions of cross sections. An equivalent bending stiffness is derived which is a function of pretwist. The principal theoretical and experimental results are shown in Fig. 4.