Scale-Model Structure Tests with Particular Reference to All-Welded Plate Girders. Discussion on Mr.

Mr. A. RAMSAY MOON, B.A., B.Eng., M.I.Struct.E., in proposing a vote of thanks to the lecturer, said that over a period of years Mr. Martin had bravely tackled a subject of
extraordinary difficulty and complexity, and the results at which he had arrived would
undoubtedly be of the greatest value in solving some of the many difficult problems which had been brought out in the paper. Mr. Martin had given them interesting information about residual stresses due to welding, he had shown them that a model girder behaved as one would expect a full-sized structure to behave, and had given them information on the behaviour of steel structures when the load impressed caused the stress to pass the yield point. At the present time an enormous amount of att,ention was being devoted to the question of the plastic behaviour of steel structures in all countries and Mr. Martin's was one of the few pieces of definite experimental work. He (Mr. Moon) thought there was no equipment available anywhere in the world for accurately measuring the extremely small distortions and deformations-particularly the elastic deformations- which had to be measured in order to ascertain the residual stresses due to welding. The only warning that Mr. Moon wished to utter with regard to the paper was that the theory of geometric similarity should not be carried too far and that it should not be assumed that, because a small girder about eight feet in length shrank three-sixteenths of an inch during the welding, a girder ten times that length would shrink about three inches. The welds in that particular case were not of exact geometrical sim.ilarity to the size of the structure and the difficulty was not experienced with the larger structure. They were greatly indebted to Mr. Martin for his most interesting and inspiring paper.