. The Americana; a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc., of the world. most successful intro-duction of reinforced concrete bridges in theUnited States, however, belongs to EdwinThacher, who was the first American engineerto design them according to the elastic theoryor the law of flexure in solid arches. His sys-tem employes a series of flat steel bars in pairs,placed parallel to each other at proper distancesapart. The top and bottom of each pair con-form to the curve of the extrados and intradosrespectively,
. The Americana; a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc., of the world. most successful intro-duction of reinforced concrete bridges in theUnited States, however, belongs to EdwinThacher, who was the first American engineerto design them according to the elastic theoryor the law of flexure in solid arches. His sys-tem employes a series of flat steel bars in pairs,placed parallel to each other at proper distancesapart. The top and bottom of each pair con-form to the curve of the extrados and intradosrespectively, and extend for some distance intothe abutments or piers. The bars of each pairare not connected with each other, but are pro-vided with rivet head projections spaced at closeintervals, which are designed to increase theadhesion of the concrete to the steel. They actin a manner similar to the flanges of an im-bedded beam and serve to assist the concrete toresist the thrusts and bending moments appliedto the arch. A greater number of concrete steelbridges are built by the Thacher system in the I Saocf and Grave/ Concrete i\ I I l-LU. f/fffSfee/Bars. Cro5s Section at Crown of Arch. Fig. 33. H United States than by any of the others de-scribed. The most notable example is theThacher Y bridge at Zaiiesville, Ghio, com-pleted in 1901. It is built at the confluence of the Muskingum and Licking rivers and has,three branches which radiate from the triangularcentral pier to the three opposite banks. the branches have three spans and the other,two spans, having a total length of 828 thickness of the arch ring at the crownvaries from 18 inches for the short spans of 81feet to 30 inches for the longer spans of 122feet, with a width of 43 feet over the arches,and 42 feet between the walls of the Fig. Z2>- Other important examples are the Jacaguasbridge in Porto Rico and the Green and GoatIsland bridges at Niagara Falls, N. Y. Theformer carries the military ro
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectencyclo, bookyear1908
