Advanced Steel Construction

Vol. 8, No. 2, pp. 183-198 (2012)



C.K. Iu * and M.A. Bradford

Centre for Infrastructure Engineering and Safety

School of Civil and Environmental Engineering

The University of New South Wales, UNSW Sydney, NSW 2052, Australia

*(Corresponding author: E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. )


Received: 31 May 2011; Revised: 10 October 2011; Accepted: 14 November 2011



In the companion paper, a fourth-order element formulation in an updated Lagrangian formulation was presented to handle geometric non-linearities. The formulation of the present paper extends this to include material non-linearity by proposing a refined plastic hinge approach to analyse large steel framed structures with many members, for which contemporary algorithms based on the plastic zone approach can be problematic computationally. This concept is an advancement of conventional plastic hinge approaches, as the refined plastic hinge technique allows for gradual yielding, being recognized as distributed plasticity across the element section, a condition of full plasticity, as well as including strain hardening. It is founded on interaction yield surfaces specified analytically in terms of force resultants, and achieves accurate and rapid convergence for large frames for which geometric and material non-linearity are significant. The solutions are shown to be efficacious in terms of a balance of accuracy and computational expediency. In addition to the numerical efficiency, the present versatile approach is able to capture different kinds of material and geometric non-linearities on general applications of steel structures, and thereby it offers an efficacious and accurate means of assessing non-linear behaviour of the structures for engineering practice.


Keywords:Beam-column, Frames, Interaction surface, Material non-linearity, Refined plastic hinge method, Strain hardening


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