Correspondence on The Economics of Steelwork Design by F.H. Needham

Professor A. L. L. Baker (F): At one time it appeared that we might use a limited tensile strain normal to uniaxial load of cube strength x Poisson's ratio / E as the general criterion for ultimate strengths for all practical purposes. Indeed, if we assume that the ratio of stress over strain at the ultimate limit state is 2 x l0 to the power 6, and that the Poisson's ratio is 1 over 4.5, we can derive, for a multiaxial strained cube, an equation that fits the mean values shown in Fig A1 in the paper. It also fits the higher ranges, if E is reduced in all the terms of the basic strain equation to agree with low values indicated by the curves in Fig A4 and provided that secondary strains do not at some point reverse.

. . spare that tree Mr. C. G. H. Jofeh is clearly a man concerned about nature conservancy. He writes: I read with interest the letter from Mr. A. Billingham (November 78). What interested me was not the question of what the building regulations do or do not say, but the attitude of mind of the author that I inferred from what he said about the trees. Verulam

Design curves and formulae are presented for the calculation of deflections in reinforced concrete flexural members. These are based on the procedure given in appendix A of CP110 for direct calculation of curvatures and deflections due to short-term and long-term effects. Using the design curves as the basis, an estimate of the errors introduced by the simplifying assumptions presently used in deflection calculation is obtained, and the area of validity of these assumptions is defined. The need for a more realistic assessment of deflections and the use of the design curves are illustrated by an optimum design example. The advantage of the design formulae and the associated curves in deflection calculations is illustrated by considering a doubly reinforced member. D.J. Gunaratnam