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DiscussionProfessor Sir Alfred Pugsley (University of Bristol) wished to begin by making the general observation that when new materials were introduced into civil engineering they were not only of immediate benefit to the profession but had also a much wider and in the long run more important effect: they gave rise to new structural problems, the solution of which caused a more general advancement of knowledge. Most new materials had had that effect, and this was very well exemplified by the Author's work. The advancement in this case had initially been of a detailed analytical character, exemplified by the Author's analysis of local buckling. But it had since led to a deepening of the understanding of the behaviour of structures generally; and the relevance of the local buckling problem to the behaviour of structures and structural components in general was illustrated in the Paper.57. There were two details in the Paper on which he wished to comment. There was an interesting little section on the tendency for a tension member, even when axially loaded in a particular distributed fashion, to twist when tension was applied. Did the Author regard this as important in practice? These light cold-rolled sections had very low torsional stsnesses; was it not very easy to suppress a twist of that sort by local connexions if it were desired to do so? 58. In another section of the Paper reference was made to the economy and efficiency of the use of cold-rolled sections and this was nicely illustrated by some curves of the permissible stresses for struts in relation to the structural loading coefficient (the end load divided by the length squared). In this graph, Fig. 22, the cross-over indicated the range over which cold-rolled sections as struts were particularly efficient. To avoid using 10-3 and the like, if one multiplied by 2,240 to bring the figures to lb/sq. in. it would be found that the cross-over occurred for a coe6cient between 2 and 4 Ib/sq. in.That was a pointer-and no doubt the Author meant it as such-to the sphere in which sections of this sort were specially valuable: lightly loaded structures where the members wererelativelylong. Therangeof structureloadingparameterincivilengineeringpractice was much wider and went up to 10 or 15 lb/sq. in., and at the upper end no one would wish to use cold-rolled sections; but that was no unusual disadvantage because all materials and all sections had such limited ranges of efficiency. 59. Sir Alfred had hoped that the Author would indicate more than he had in fact done the work to which he looked in the future. It might be that he felt that local buckling had had its day. He had done his work so well that he might not want to touch it up further, but what did he think was the next step? One possible step came to mind on reading the introduction to the Paper, in which it was pointed out that the process of forming cold-rolled sections cold-worked the material very heavily where the plate was bent most, at the "corners", so that the local hardness went up. One wondered ...

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