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The Structural Engineer, Volume 65, Issue 2, 1987
Shortcuts in design It may seem to our readers, as it did to us, that we receive a large number of letters giving shortcuts to the design of reinforced concrete in bending. It appears, however, that we published only one letter on this subject last year, from Mr P. H. Gregory, which appeared in October in outline only, since it set out two programs for a ‘home’ computer. We have now received the following offering from Mr R. N. Morgan of Edinburgh: I have identified an expression that can be used for the direct calculation of A, that is applicable to the rectangular concrete stress block of CP 110 and also to the ‘Beeby’ stress block of BS 8110 as well as the so-called ‘exact’ rectangular/parabolic stress blocks applicable to both Codes. The derivation of the expression is enclosed for your information. Verulam
The paper discusses the use of structural fire engineering techniques as a method of satisfying the functional requirements listed in the 1985 revision of the England and Wales Building Regulations. C. Ian Smith
This paper presents comprehensive test data on the effect of glued steel plates on the first crack load, cracking behaviour, structural deformations, serviceability loads, and ultimate strength, of rein forced concrete beams strengthened with such plates on the tension face. The results show that plated beams have enhanced flexural stiffness which control cracking and deformation at all load levels until failure. However, the stiffening effect is much greater in controlling cracking; further, the structural effect is far greater than if the bar area had been increased by the same area as the plates. Provided the adhesives are chosen carefully and proper gluing techniques are followed, the plated beams show beam action and composite behaviour right up to failure. The glued plates can increase the ultimate flexural strength by up to about 15 %. There is, however, a limit to plate thickness beyond which premature shear/bond failure occurs without the beams achieving their full flexural strength, even though such beams still control cracking and deformation until failure. The paper suggests two tentative design criteria to ensure full flexural capacity and ductile failure of plated beams. R.N. Swamy, R. Jones and J.W. Bloxham