Nonlinear frame analysis by the pseudo load method

A methodology for the analysis of frame structures taking into consideration geometrical and material nonlinearities is presented. The method was developed by exploiting the similarity between the differential equations of a beam-column and a beam. The effect of geometrical nonlinearity is accounted for by applying pseudo loads to the frame. The effect of material nonlinearity is accounted for by using a moment-curvature-thrust (M-Φ-P) relationship for cross-section plastification and a modified member stiffness relationship for member plasticification. The validity of the method is demonstrated by comparison with existing theoretical and numerical models. The major advantage of the proposed method is that convergence of solution is almost guaranteed. In addition, the analyst has complete control of the degree of accuracy of the problem. The merits of the method will be demonstrated by numerical examples of member and frame analyses.