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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.
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.
Oscillation of a structure induced by vortex excitation is likely to occur at frequencies quite different from the natural frequency of the structure because of the locking-in phenomenon. Effective damping by means of a passive mechanical system requires that the system be capable of operating over a large range of forcing frequencies under the exciting forces which may vary in direction and intensity. A damping device based on the principle of energy dissipation by impact has been developed for this purpose. It has a nonlinear response to displacements, and is suitable for operation at relatively low frequencies. Selected experimental results are
presented in this paper.