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The paper bearing the above title, which appeared in “The Structural Engineer” for October was read at the meeting of the Institution of Structural Engineers held on October 24, at 10, Upper Belgrave Street, S.W.1, the chair being taken, in the absence of the President, Colonel Moncrieff, by Mr. S. Bybancler (Member of Council). The discussion which ensued was adjourned to Thursday, November 7, when it was again resumed under the chairmanship of Mr. Bylander. The proceedings of both dates are reported below. Owing to limitations of space it has not been found possible to publish the discussion in extenso, while, for the same reason, it, has been found necessary considerably to condense the remarks made by individual speakers who took part in that discussion.
THE CHAIRMAN, Major F. M. Du-Plat-Taylor, said hc noticed that the paper was roughly divided into two sections, one dealing with piles and the other with the building. The piling was an extremely interesting system. Of course, there had been many systems of tubular piling of that sort, by which the concrete was poured through a tube which had been previously driven, but some of the systems which had hitherto been in use had not, in his opinion, been very satisfactory. Many years ago he drove a large number of piles on a tubular system; the tube was merely withdrawn after it had been filled with concrete, and they had some very disquieting results after the piles had been driven. In one case, although the piles had been well driven into the ballast, about 60 ft., some of them subsided 15 inches without any particular load. That led them to strip one of the piles and examine it, and they found that there was a distinct "waist" in one or two places where the soil had compressed the concrete, so that instead of there being a 15-inch pile there was only about six inches of concrete at that particular point. Another difficulty that they had was maintaining of the reinforcement in position. In some of the piles the reinforcement, which should have been central, had become displaced; sometimes on one side it was touching the surface, on the other side there were four or five inches of cover. To overcome that difficulty they had to adopt various methods. They had spreaders which touched the inside of the tube and maintained the reinforcement central. That was, of course, objectionable, because when the tube was withdrawn the spreaders were left sticking into the ground, so that there was a connection of metal between the steel and the surrounding soil. The system of pouring the concrete without ramming it had now been entirely superseded by the system which Mr. McCarthy had described, which overcame the whole of the objections to the previous systems. It was a very speedy method, and the ridges formed on the cutside of the pile probably contributed to the frictional resistance. He could confirm what the lecturer had said regarding noise, because his office almost overlooked the St. James’ Park site, and he noticed the extraordinary difference when the silencers were adopted. He would like to ask Mr. McCarthy whether any special method had to be adopted to maintain the reinforcement central, and whether any difficulty was experenced with the reinforcement moving to one side or other of the pile. The second part of the paper, dealing with the building, was particularly interesting on account of the great rapidity with which it was erected. He mas sorry that Mr. McCarthy had said nothing about the statuary. It was a very striking building for one particular reason-the cruciform plan. The cruciform plan had been adopted pre viously in prisons, in order that a warder standing in the middle of the cross could see the corridors in all directions. It had also
The articles by Mr. W. Basil Scott, in The Structural Engineer, for November, 1928, and August, 1929, on what he terms "Augmented Steel," must be of great interest to many engineers, like myself,who are dissatisfied with the uneconomic method of designing concrete-encased structural steelwork on the common assumption that, the steel derives no assistance from the concrete but, on the contrary, has to support it as a dead load. Such designing retards progress towards the best use of modern building materials or, as Mr. Scott has expressed it, "The practice imposes an unfair penalty on economic steelwork design." N.B. Carson