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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
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.
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.