Abstract:
This research presents a principle of second-order elastic-plastic analysis of rigid steel frames. Beam-column member stiffness using small displacement theory include axial force is formulated in the form of stability functions. Newton-Raphson method using tangent stiffness approach, then is used for solving simultaneous nonlinear equations. Convergence is accomplished by specifying Euclidian norms to be smaller than convergence criteria required. Direct increment method is used for elastic-plastic analysis. Plastic moment capacity reduced due to the presence of axial force is considered by using AISC proposed expressions. Results obtained from the presented analysis have shown to be in close agreement with the existing results. Proposed predicted ultimate load factor are about 5 percent deviated from the others. The proposed method, however, is very handy for analysis of rigid steel frames in 4 alternatives approaches, i.e., first-order elastic, second-order elastic, first-order elastic-plastic and second-order elastic-plastic analysis.