Issue 6

MR. FORDHAM, in a brief preface to his paper, said that those who had studied modern books on arches, and who were perhaps not very closely interested in arch theory, had been rather frightened off the subject by the calculus and by the algebraic symbols.

With the extensive use of reinforced concrete for modern bridge construction, semicircular, segmental and semi-elliptical arches of brick, plain concrete or stone are much less frequently adopted for new works than was formerly the case; but the revival of road transport occasioned by the use of the petrol driven vehicle brings home to the structural and civil engineer the importance of the problem of the stability of the arch. Arthur A. Fordham

In connection with the general scheme for the improvement of vehicular transport between the various districts of New York City and the outlying townships, four important new bridges are included. These are a high-level cantilever bridge across the Arthur Kill between Perth Amboy, New Jersey and Tottenville, Staten Island, N.Y., named "The Outerbridge Crossing;" a second high-level cantilever bridge also over the Arthur Kill between Elizabeth, N.J., and Howland Hook, Staten Island, N.Y., and named the Goethals Bridge. Both these bridges are approached by long viaducts of plate girder deck spans. Their location will be seen on the accompanying plan, and the general character of the bridges will be appreciated from the illustrations. The third bridge is over the Kill van Kull, and the fourth is the Hudson River Bridge of 3,500 feet span, which was described in considerable detail in our April issue. These four bridges, when all are opened for traffic, will represent an investment of closely one hundred million dollars, of which amount more than half has been already expended or contracted for.

The following short article is quoted from the Proceedings of the American Society of Civil Engineers, Part 2, May, 1929. It is not recent, but will probably be of general interest to members :- Between 1O and 15 years ago extensive studies were made by experienced investigators, Sidney and Beatrice Webb, covering the development and status of professional associations in England. Special interest attaches to this because it was completed and published in the midst of the World War. What follows is abstracted or quoted from “The New Statesman,” a forward-looking British weekly. The material appeared in two parts, as special supplements to the issues of April 21 and 28, 1917.

By the courtesy of Mr. 0. H. Ammann, Chief Engineer of Bridges to the Port of New York Authority, we are enabled to give the following resume of the progress made in the erection of the 3,500-ft. span bridge over the Hudson River since the publication of the First Progress Report rendered'on January 3, 1928. The difficult and deep foundations for the New Jersey Tower, commenced in the summer of 1927, were successfully completed early in 1928. The contract for the construction of the tower base on the New York side was let in May and completed within two months. This foundation, unlike that on the New Jersey side, involved only the comparatively simple operation of building two massive concrete blocks on sound rock above water level. Rolling of the 40,000 tons of steel for the towers began late in 1927, and throughout 1928 the fabrication of this steelwork proceeded continuously at three of the largest bridge shops. Actual erection of the towers began in June, 1928, and within four and a half months 31,000 tons of steel had been erected and the towers had reached a height of 500 feet. Erection work was then suspended until the spring of 1929. Work on the anchorages meanwhile proceeded intensively. The excavation of 200,000 cubic yards of hard traprock for the New Jersey anchorage and approach is now practically completed. On May 4, 1928, the contract was let for the excavation for and building of the gigantic blocks constituting part of the New York anchorage in Fort Washington Park. This contract entails the placing of closely 110,000 cubic yards of concrete, and so efficiently has the work been carried on that nearly 100 per cent. has already been completed, several months ahead of contract time.

Silica forms 60 per cent. by weight of the earth’s crust, and as the Great Architect of the Universe has chosen silica for the frame of this earth, so the structural engineer, in his infinitely humbler capacity, uses it to form about 60 to 70 per cent. of the weight of concrete. E.F. Sargeant