Nonlinear Behavior of Structural Plane Frames

The deformations that occur in an actual structural frame may significantly influence the joints’ equations of equilibrium and hence the theoretical load-carrying capacity. The finite deflection theory is introduced to deal with the influence of finite displacements on the behavior of structural frames. The method is applied to rigid-jointed pitched roof portal frame and the results are presented in the form of nondimensional graphs. The bowing functions (b\D1\N and b\D2\N) and stability functions (s and c) influence significantly the behavior of this type of frame at high load parameter which indicates their importance for the estimation of the theoretical load-carrying capacity. The classical phenomenon of elastic critical load needs to be reconsidered since the load-deflection curve does not produce the buckling phenomenon. In general, the nonlinear behavior of structural frames as influenced by instability, bowing and finite deflections are studied. A relaxation method has been developed for solving the problem because direct solution is not possible.