Erection of Metallic Bridges - Discussion on Mr. Adam Hunter's Paper

TO the Editor of "The Structural Engineer.” Sir,-I was unfortunately unable to be present at Mr. Bossom’s paper, and was somewhat surprised to note that neither in the paper nor in the discussion was any reference made to the sections which are now being rolled by the Carnegie Steel Co. and marketed by the United States Steel Products Co. These new sections include a 14 in. H section, maximum weight which is 305 Ibs. per foot, with sectional areas of 89.7 square inches. For column lengths not exceeding 20 ft. this is listed to carry 1,346,000 lbs.

Under the above title and from the pen of Mr. Sathan C. Johnson, Consulting Engineer of New York City, there has,recently appeared a series of four articles in Engineering News-Record, which should be read by everyone honestly interested in the betterment of the production of concrete in large or small quantity. These articles constitute a carefully considered and thoughtful review of the extent to which the existing practice of producers comes up to the demands of consumers. In plain language, are the best efforts being directed to the production of a uniformly high quality of concrete on the works and is the best interpretation being put upon the mass of valuable information accumulated from failures, practical tests and laboratory research during the past two decades? During that period we have undoubtedly advanced a long way on the road towards a thorough understanding of the interactions which take place when water, cement, sand and stone are mixed together in varying ratios, yet the further we advance, the more does it become apparent that this seemingly simple material is actually most complicated in its properties and behaviour. The state of our knowledge of the chemistry of cements is still far from complete. We have reached a stage, however, when, given the necessary time and leisure, small quantities of laboratory-made concrete may be produced which, under meticulous testing exhibit remarkably high strength properties. The methods by which such iaboratory samples are produced obviously cannot be applied to the production of concrete in bulk. As Mr. Johnson aptly remarks, "On the job, cement is cement, sand is sand, stone is stone, water is water and weather is weather. No time for niceties, no leisure for reflection and, perchance and even possibly, a most wordy flow of language here and there to speed the laggard hand. Men and machines and materials in an unceasing stream are everywhere in evidence, all governed by, the plans prepared by the engineer or the architect and, presumptively, by the specifications."

In the year 1926 was commenced the construction of the world's largest bridge. The year 1932 is expected to witness its opening to traffic. Its ofiicial name is the Hudson River Bridge and it will span the Hudson River between Fort Washington in the State of New York and Fort Lee in the State of New Jersey. This bridge will provide highway and electric railway transit over the main channel of the Hudson River. Its location, together with that of other links between New York, Brooklyn, Manhattan and New Jersey, is indicated in Fig. 1. The bridge is being built by the Port of New York Authority, pursuant to authority conferred by joint action of the States of New York and New Jersey. The financing was effected by the Port Authority authorising an issue of 60 million dollars, Port of New York Authority, New York-New Jersev Interstate Bridge Gold Bonds, 30 millions of which were sold on December 9, 1926, to the underwriters; and by the States of New York and New Jersev, by appropriate legislation, making available to the Port Authority the sum of 10 million dollars. The 20 millions of bonds sold to the public bear interest at the rate of 4 per cent. They were sold to the public on a basis to yield 4.20 per cent., and are today selling in the open market on a 4 per cent. yield basis. Professor J. Husband