TABLE OF CONTENTS The literature on classical analysis of anisotropic beams shows that, when all three one-dimensional moment strain measures (i.e., twist and bending curvatures) are of the same order, the resulting cross-sectional analysis is linear. Recall that for class S beams, two of the one-dimensional moment strain measures are larger than the third, and that for class 
beams one of the one-dimensional moment strain measures is larger than the other two. Here it will be shown by illustration how these situations lead to nonlinear cross-sectional analyses. This type of nonclassical analysis is needed, for example, in problems where the trapeze effect is important, such as in rotor blades. Study of this section may help the reader to better understand the relatively complex nonlinear sectional analysis of arbitrary cross-sections, presented in Sec. II.G of Chapter 4.
In this section a nonlinear sectional analysis is presented for an anisotropic strip with small initial twist, based on the dimensional reduction of laminated shell theory to a nonlinear one-dimensional theory using the VAM. Results obtained from this strip-beam analysis are compared with available theoretical and experimental results for a problem in which the trapeze effect is important. In order to demonstrate the usage of the results in the analysis of structures made of an arbitrary geometrical combination of initially twisted, generally anisotropic strips, a closedform expression is derived for the torsional buckling of a column with a cruciform cross-section.
Modeling of beam-like anisotropic structures having initial...
