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MR. M. GREGORY congratulated the Author on his paper, and referred to existing methods for calculating the critical load of a triangulated framework, as mentioned in the introduction. That critical load was the buckling load for the “mathematically perfect”
structure, assuming perfectly straight members, no eccentricity at the joints, and no yielding. The problem was to relate the behaviour of the practical structure having practical imperfections such as initially crooked members, eccentricities at joints, and having a finite yield strength, to the mathematics of the perfect structure, and, in particular to find the collapse load of the practical frame. The collapse load of a light flexible frame made of material of high yield strength might be close to the calculated criticaload, but unfortunately, for structures containing members of stiffness in the practical range, this was not the case. Therefore, any attempt to tackle the problem of studying the behaviour of practical frames proportioned in a realistic manner was worthwhile. Some method of taking account of the practical imperfections of framed structures was urgently needed.
The necessity for ever increasing elevation of buildings arises from a number of causes, and while these reasons do not form any part of the design and construction problems involved, they are, in the author’s view, worth stating.
Lt.-Colonel G. W. Kirkland
A general elastic moment distribution method is presented, capable of application to all types of rigid space frames. The method employs matrices of stiffness and 'carry-over' terms, and the procedure is equivalent to the well known Hardy Cross process of analysis. The method is illustrated by typical problems.