Professor R. P. Johnson (F) (University of Warwick): It is shown by numerical analysis in this paper that simply supported, open sandwich, steel reinforced concrete beams are not susceptible to failure by propagation of a crack along the adhesive layer. This is consistent with the results of a series of tests published in 1981, in respect of cracks that initiated within the length of the steel plate.
The paper discusses movements in brick masonry caused by creep and considers its effect on prestress losses in post-tensioned brickwork. It follows almost 2 decades of research in which various specimens comprising brickwork walls, columns, and beams, with different types of brick and mortar, have been subjected to a sustained load at different stress levels. From the information obtained, a number of expressions are put forward for creep coefficients which can be fed into a simple theory for predicting prestress losses in post-tensioned brickwork members. A creep-time function was also obtained which was used in comparing experimental and theoretical creep strains in a loadbearing brickwork tower block, during its construction stage and later life. D. Lenczner
The results of 13 tests of post-tensioned I- and T-beams are presented. All but two of the beams contained inclined tendons and all but two failed in shear. The recommendations of the British and European Codes are reviewed and compared with the present and other test results. It is shown that the British Codes are unsatisfactory and that the CEB recommendations, while somewhat more logical, also leave much to be desired. A very simple approach to the subject is proposed, based on a truss model. The model is shown to give satisfactory agreement with experimental behaviour and ultimate strengths. H. Rezai-Jorabi and P.E. Regan
Buckling tests were carried out on 38 slender reinforced concrete deep beams having height:thickness ratios in the range 25 to 67. Observations were made on the ultimate loads and failure modes. The variables studied included the height:thickness ratio (h/b), the clear-shear-span:height ratio (x/h), and the load-eccentricity:thickness ratio (e/b). The observed behaviour and failure modes of the slender deep beams were described and compared with those of stocky deep beams as reported in the literature. The measured ultimate loads were compared with values predicted using CIRIA Guide no.2: The design of deep beams in reinforced concrete. These tests, which for the first time enabled the CIRIA buckling-load predictions to be checked against experimental values, have confirmed the CIRIA guide as a safe design document. For very slender deep beams, the CIRIA buckling predictions tend to be too conservative. Professor F.K. Kong, R.C. Garcia, J.M. Paine, H.H.A. Wong, C.W.J. Tang and M. Chemrouk