. The street railway review . ouble-decked truss. The lowerwest approach span, carrying the local tracks, is a through upper west approach span is of deck construction with the ends reverse curve into the center of Market St.; from there westwardthe longitudinal girders will be of lattice construction. The sund-ard longitudinal lattice girders are 50 ft. long. The width of thestructure is 24 ft. from center to center of columns. The underclearance between head of the surface track rails and the lower sideof the transverse girders has a minimum limit of 14 ft. The foundations for the c
. The street railway review . ouble-decked truss. The lowerwest approach span, carrying the local tracks, is a through upper west approach span is of deck construction with the ends reverse curve into the center of Market St.; from there westwardthe longitudinal girders will be of lattice construction. The sund-ard longitudinal lattice girders are 50 ft. long. The width of thestructure is 24 ft. from center to center of columns. The underclearance between head of the surface track rails and the lower sideof the transverse girders has a minimum limit of 14 ft. The foundations for the columns, a typical one of which is illus- S24 STREET RAILWAY RIAIFAV [ XV, No, g. tratcd, are of concrete with four anchor bolts to each bolts are buried to a depth of 4 ft. 6 in. in the concrete massof the piers. In many cases, gas and watcrpipes arc so close to thestreet surface that it was necessary to provide grillages with beamsowing to insufficient depth for reinforced concrete construction to ~-»-£S-. ^iJll^lf *.JU.!Ui/. SECTION OF \TED ST.\TION. carry tlic columns. .•\11 steel work in grillages of this kind is en-cased in concrete, the concrete being locked to the sides of thevertical surfaces to maintain permanent contact and prevent cor-rosion. On filled or soft ground special designs for foundationswere necessary and spread footings of reinforced concrete werebuilt to make the unit pressure low. When the bases of the columnsare permanently set over the anchor holts, a cast iron fender placedaround the base of each column is filled with concrete. The upperportion of this fender is open to permit of the proper tamping ofthe concrete, and when the interior is filled the upper surface istroweled to a smooth finish. The columns are I-shape and are made up of two 15-in. chan-nels, to the a.\ial line of which is fastened a 14 .x }i-m. web, theconnection between the parts being made by four 4 x 3V2 x J^ irons. These columns have base plate
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Keywords: ., book, bookcentury1800, bookdecade1890, booksubjectstreetrailroads
