The encyclopdia britannica; a dictionary of arts, sciences, literature and general information . as a span of 278 ft., 138 ft. riseabove; the river, and 102 ft. from foundation to crown. Thethickness of the arch is,4 ft. 8 in. at the crown and 7 ft. 2 it joins the spandrel masonry. /jThe roadway is 52 ft. 6 The bridge is not. continuous in width, there are archrings on each face, each 16-4 ft. wide with- a space between of19-7 ft. This space is filled with a flooring of reinforced concrete,resting on the two arches, and carrying the central the method adopted the t
The encyclopdia britannica; a dictionary of arts, sciences, literature and general information . as a span of 278 ft., 138 ft. riseabove; the river, and 102 ft. from foundation to crown. Thethickness of the arch is,4 ft. 8 in. at the crown and 7 ft. 2 it joins the spandrel masonry. /jThe roadway is 52 ft. 6 The bridge is not. continuous in width, there are archrings on each face, each 16-4 ft. wide with- a space between of19-7 ft. This space is filled with a flooring of reinforced concrete,resting on the two arches, and carrying the central the method adopted the total masonry has been reducedone-third. One centering was used for the two arch rings,supported on dwarf walls which formed a slipway, along whichit was moved after the first arch was built. Till near the end of the 19th century bridges of masonry orbrickwork were so constructed that they had to be treated asrigid blockwork structures. The stability of such structuresdepends on the position of the line of pressure relatively to theintrados andT extrados of the arch ring. Generally, so far as. Fig. 9.—Half Elevation and Half Section of Arch of LondonBridge. could be ascertained, the line of pressure lies within the middlehalf of the depth of the voussoirs. In finding the abutmentreactions some priliciple such as the principle of least action mustbe; used, and some assumptions of doubtful validity made. Butif hinges are introduced at crown and springings, the calculationof the stresses in the arch ring becomes simple, as the line ofpressures must pass through the hinges. Such hinges have beenused not only,for metal arches, but,in a modified form formasonry and concrete arches. Three cases theirefore arise:(ay The arch is rigid at crown and spjiingings; (6) the arch istwo-hinged (hinges at springings); (c) the arch is three-hinged(hinges at crown and springings) .For an elementary account ofthe theory of arches, hinged or not, reference maybe made to a joint by more than one-eig
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectencyclo, bookyear1910
