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Dear Sir, I am not altogether surprised to find what appear to be misprints in the calculations given in Fig. 4, as similar misprints were tound in the published calculations for an even larger structure, the Sydney Harbour Bridge, but too late to bring the matter up at the time. In the present paper there appear to be three points in Fig. 4 which require elucidation.
Before the inception of the British Grid System for electricity supply, the overhead electric transmission lines then existing were nearly all of low and medium voltage. The 132 kV. Primary Lines of the British Grid therefore set a new standard in this country, not only of the voltage of the lines and the power they were to transmit, but also as regards the size of conductors, tower heights, spans between towers, and degree of reliability demanded. These factors had their influence on the design of the towers, as the loads to be sustained, both under normal and abnormal (broken conductor) conditions, were much greater than was usual in this country previously. H.W.B. Gardiner and W.H. Gomm
Professor A. L. L. Baker (Member) opened the discussion by saying that he agreed entirely with what the authors had said in their presentation but not with what they had written in the paper. He agreed with the statistical, probabilistic approach. It was obviously the only logical way of dealing with the variations of strengths of materials and the variations and vagaries of loading. There were one or two points in the paper which Professor Baker found slightly misleading. First of all, the matter of basing a design entirely upon a probability of failure-10-7-and a minimum cost, and saying that one could not entirely guarantee a structure against failure, needed some qualification. He thought this was rather a dangerous statement.