THE PRESIDENT proposed a vote of thanks to Mr. Mason, first for having taken the trouble to write his paper in time for it to be published in THE STRUCTURAL ENGINEER so that members could read it before coming to the meeting, and secondly, for his clear exposition of certain of its salient points.
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
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.
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. B. Rawlings
The paper describes a method of analysis for beam and slab (or plate) systems. The theoretical analysis in its general form may be used to solve various loading conditions, but the computational work tends to be excessive. For the particular case of a uniform load over the whole area of the stiffened slab, however, the results of the analysis may be expressed as a set of coefficients the values of which may be represented graphically. For uniform loading, therefore, the method of analysis is suitable for design purposes. M. Holmes