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THE CHAIRMAN (Mr. Walter C. Andrews, O.B.E., M.I.C.E., Vice-president), introducing Dr. Hendry, referred to his earlier paper on “An Investigation of the Stress Distribution in Steel Portal Frame Knees,” in 1947, for which he was awarded the Sessional Medal and Research Prize From that and his other contributions, listed in the papers now before the meeting, it seemed that Dr. Hendry had made a “corner” in
portal frame knees and allied matters.
The development of satisfactory design rules for beams of slender proportions, which are prone to lateral instability, has taken place gradually since the introduction of the first rolled sections, over a century ago. Until the presentation of rational data in the recently revised B.S. Code of Practice for the "Structural Use of Steel in Buildings", design formulae have been of an empirical nature. These were based on the
conception that lateral buckling was entirely due to collapse of the compression flange of a beam, as a strut under variable end load. In consequence the formdlae
gave estimates of load carrying capacity which were often considerably in error, as a result of neglecting the torsional stiffness of the member.' The new design rules
are based on the mathematical theory of stability and will give reasonable estimates of the limiting stresses in beams whose slenderness ratios exceed a certain minimum value, in the same way that the Euler formula proves satisfactory in calculating the critical stresses in slender struts.
The authors have presented an interesting method for the rapid estimation of maximum bending moments in decks of suspension bridges. Their approximate analysis draws to a
logical conclusion the more general method described by Bowen and Charlton (reference 3 of the paper). It is clear that the use of symmetry and antisymmetry offers a considerable computational advantage :two sets of three linear simultaneous equations are solved far more quickly than one set of six.
F. Van der Woude, M.S. Gregory and H.I.A. Hegab