Generalized variational principle on nonlinear theory of naturally curved and twisted closed thin-walled composite beams

Naturally curved and twisted closed thin-walled slender beams of composite material undergoing small strains, large displacements and rotations have b een investigated, and an incomplete generalized variational function on the ory of elasticity with finite displacement is established far these beams w ith complete constrained boundaries at two ends. The balance equations as w ell as all boundary conditions concerned have been deduced from functional stationary value condition. The above-mentioned method can also be extended to other various incomplete constrained boundaries conveniently. In additi on, the fundamental equations and concerned formulas in the small displacem ent theory of the beams can be derived by using above results.