Revisiting the moment distribution method : buckling of beams and frames

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)Comment/debateNot applicable

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Original languageEnglish
Pages (from-to)172-179
Journal / PublicationHKIE Transactions Hong Kong Institution of Engineers
Issue number3
Online published12 Oct 2017
Publication statusPublished - 2017


It is known that when a structure is in neutral equilibrium, only infinitely small disturbing forces are required to maintain the structure in the buckled mode. By making use of this basic principle, it is proposed in this paper that the moment distribution method (MDM) can be further extended, as a complementary and handy tool, to calculate the critical elastic buckling loads of beam- and frame-type structures. To this end, the effect of axial forces are taken into account through classical stability functions. By assuming an initial axial force distribution, the fixed-end moments, carry-over factors and member stiffness are computed accordingly. Moment distribution is then performed in the usual way, except that repeated trials with different axial forces are necessary until the critical value is found. To demonstrate the concept and implementation of the method, continuous beams and portal frames with side sway are considered in this paper. In the numerical examples presented herein, the buckling loads found are compared with those obtained from commercial software so as to demonstrate that the MDM is a simple, accurate and physically-intuitive method for assisting engineering students and practising engineers with understanding the behaviour of structures and providing a quick check to output from commercial software.

Research Area(s)

  • buckling load, elastic stability, Moment distribution method