Loss of Steel Stresses in Prestressed Concrete Blockwork Walls

The influence of the type of loading and conditions of lateral support on the lateral buckling of cantilever beams is examined. In particular, it is shown that loads applied at the level of the top flange at points free to twist represent a particularly severe condition for cantilevers. The influence of various types of restraint at the tip or at the fulcrum in the case of continuous members is shown to be considerable, large increases in stability being possible. In all cases results are presented in the form of a series of simple expressions which permit the rapid calculation of good estimates of the critical load. The problem of specifying effective length factors for use in current methods of design is considered in some detail and two methods are proposed for their determination. D.A. Nethercot

Mr. Coffin: I am pleased that so many members of the drafting committee for the report Design for industrial production are taking part in this discussion. Because of the nature of the report, the committee was composed of a number of members each with a depth of experience in one of the facets of structural design. We were therefore able to collect the results of this experience over a wide range of different materials and methods of construction.

Dr. Hannant's paper candidly shows that there is still a need for devising a logical method for testing the true tensile strength of concrete.