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The Structural Engineer, Volume 48, Issue 1, 1970
Professor Arthur Bolton, Dr. I.D. Armstrong and Mr. J.F. Doyle: ‘Referring to the derivation of S we feel that the expression has an error resulting from a simple oversight.'
Mr. R. A. D. Noble: ‘In their paper Bobrowski and Bardhan-Roy put forward a simple empirical method for calculating the ultimate strength of reinforced and prestressed concrete beams in combined flexure and shear which applies equally to rectangular and I sections. The treatment of the test results in this paper leads me to the conclusion that the actual thickness of the web in prestressed I beams does not play such a significant part in determining the actual ultimate strength in combined flexure and shear as it would appear to do either in existing design practice based on principal tensile stresses, or in new proposals for the Unified Concrete Code. It is of particular interest that some of the data is taken from tests at elevated temperatures under exposure to fire, since recent proposals by the FIP, which are likely to be adopted in this country, recommend limitations to the thickness and slenderness of webs in this context. In view of the material presented in this paper it seems to me that these proposals might be unnecessarily restrictive.
The paper describes the main features of the design and construction of three 74-storey blocks of flats for the Royal Burgh of Ayr in the Bison Wall Frame System, an industrialised load-bearing wall system using large floor and wall panels of precast concrete. D.H. Orme and S. Thorburn