A study of the nonlinear in-plane warping in open thin-walled composite bea
ms is presented. The analysis is based on a generic nonlinear formulation o
f the governing equations for the in-plane deformation which are solved by
a numerical minimization procedure. The minimization process employs energy
considerations to determine the in-plane-warping deformation of generic el
astically coupled orthotropic beams. The study shows that open thin-walled
orthotropic composite beams are much more sensitive to the in-plane-warping
deformation than similar isotropic beams. In addition, it is shown that th
e in-plane warping poses an upper limit to the possible applied load. To ex
tend the applicability of the present formulation, a discrete formulation o
f the governing equations for generic open geometries is also presented. Th
e results are accompanied by an analytic approximation for open rectangular
cross-section that clarifies the nonlinear nature of the problem. (C) 2000
Elsevier Science Ltd. All rights reserved.