A New Plastic Hinge Method for the Nonlinear Analysis of Steel Space Frames(I)

A numerical method for the nonlinear analysis of steel space frames subjected to cyclic loading is presented. It is a kind of plastic hinge method, and plastic deformations in the plastic hinge are obtained by integration of generalized plastic strains (axial plastic strain ερo, biaxial plastic curvatures φρy and φρz and warping plastic curvature φρω) of the member along the assumed length lρ of elasticplastic region respect to the member axis. The non-stationary hysteretic stress-strain relation of material and the effects of large deflection "are taken into account. In the present paper the fundamental theory of the method is given in detail showing a few analytical results to examine propriety of the basic concept of the method on (1) ultimate load behavior of curved I-beams; (2)inelastic behavior of wide flange beam-columns under constant vertical and tow-dimensional alternating horizontal loads