Second-order plastic-hinge analysis of planar steel frames using corotational beam-column element

A new beam-column element for nonlinear analysis of planar steel frames under static loads is presented in this paper. The second-order effect between axial force and bending moment and the additional axial strain due to the element bending are incorporated in the stiffness matrix formulation by using the approximate seventh order polynomial function for the deflection solution of the governing differential equations of a beam-column under end axial forces and bending moments in a corotational context. The refined plastic-hinge method is used to model the material nonlinearity to avoid the further division of the beam-columns in modeling the structure. A Matlab computer program is developed based on the combined arc-length and minimum residual displacement methods and its results are proved to be reliable by modeling one or two proposed elements per member in some numerical examples. (C) 2016 Elsevier Ltd. All rights reserved.