Mr K. C. White (President, Institution of Structural Engineers): Your Royal Highness, distinguished guests, ladies and gentlemen: I started to put these words together during a break while attending the 13th IABSE Congress held in Helsinki some 2 weeks ago. The theme of that Congress, and one that Oleg Kerensky would greatly have enjoyed debating, was ‘Challenges to structural engineering’. Session subjects like the ‘Application of advanced materials’, ’Structural repairs under exceptional circumstances’, and ‘Long-span structures’, would have been almost self-indulgence to him.
Chairman: It occurs to me that the logical development of the work the authors have done is to extend the span of traditionally slender steel construction. I understand that the idea is to minimise the cost by reducing the fabrication cost. As these members get more slender, presumably deflection begins to become critical. Is any research being done concerning the possibility of using post-tensioning or prestressing techniques applied to steelwork, which was the logical development in concrete? Is any corresponding work being done in steelwork?
The shear resistance of vertical plane joints between large, precast concrete panels is investigated experimentally. A total of 18 specimens with varying joint width, number and shape of bars in the joint and shape of section were tested under pure shear, shear and compression or shear and bending. Results obtained are compared with the available theoretical method, as well as with the design provisions of BS 8110 and the ACI Code. A general prediction model isproposed, taking into consideration the combined effect of the dowel action of the reinforcing bars and the shear resistance of concrete, under different types of loading. The model gave lower bound values which are in better agreement with experimental results, with a factor of safety of 1.15. It is also concluded that the width of plane joints has a significant effect on the shear resistance and should not be neglected in design. Professor H.M.S. Abdul-Wahab and S.Y.H. Sarsam
Support of slabs in cavity wall construction Since Mr J. M. Golding first raised the question in November last year, our correspondents have been teased by the problem of how to satisfy BS 8110 in the placing of rein forcement at the ends of slabs simply supported on cavity walls. Mr A. H. Ferrier, of Bridgnorth in Shropshire, now offers to clear away our worries on this particular score, the while pointing out the need for a little healthy scepticism when Codes appear to conflict with commonsense! Verulam