Issue 1

We have read this paper with interest and its contents have prompted us to express the following opinion on structural analysis in general. B.I. Maisel. G. Elliott and L.A. Clark

Emeritus Professor A. L. L. Baker (F) who from 1945-1973 was Professor of Concrete Structures and Technology at Imperial College, London, writes: The Report of the BRAC Sub-committee on high alumina cement concrete in buildings (The Structural Engineer, October 1975, p. 431 ) deals with a very complicated problem. May I comment and enquire if the following interpretation of the recommendation for calculating the ultimate resistance moment of an X-beam is correct.

For some years, research has been carried out at the Cement and Concrete Association to study the relative structural merits of different reinforcement arrangements for certain common situations in reinforced concrete structures. This work was started partly because a few failures had occurred in practice and partly because there was a lack of basic data on how detailing affected strength. Early projects were therefore concerned with specific areas where problems had been experienced either in practice or in previous research projects and were aimed at determining the optimum steel arrangement purely in terms of strength. Topics covered at this stage included half-joints, flexural corners and compression splices in columns; the structural efficiencies of these were reported in a previous paper presented to this Institution'. H.P.J. Taylor and J.L. Clarke

The Cruachan Viaduct, carrying the Tyndrum-Oban trunk road A85 along the north shore of Loch Awe, was strengthened during the 1930s, but became inadequate for present-day traffic and a further major construction has recently been completed. E.H. Cooley

Effects of geometric imperfections in the form of the meridians of hyperboloidal cooling towers are re-assessed. It is shown that even moderate imperfections induce hoop stresses in the vicinity of the imperfection that are of the same order of magnitude as the meridional stresses that would occur in this same area of the perfect shell. K.O. Kemp and J.G.A. Croll

The duties and responsibilities associated with Building Regulations continue to stimulate what is, we are sure, a most useful and interesting discussion. Mr. F. D. Entwisle added to his succinct contribution (October 75) a further commentary stimulated by the observation of Mr. R. E. Musson and ourselves: I would like to comment on Mr. R. E. Musson's contribution and the last paragraph of your observations (October 75). Verulam