A Treatise On The Principles And Practice Of Dock Engineering

BASCULE BRIDGES AT CHICAGO. 447 Name of Bridge. Width of Plat- form. Width of Pass- age. Weight of Super- structure. Remarks. 1 2 3 4 5 6 7 Keizersbrug, Stokkenbrug, Nieuwe Oostbrug, Jan Kuitenbrug, . Spangaardsbrug, . NieuweLeuvebrug, Scheluwebrug, Feet. 23 28 254 29 29 32 32 Feet. 33 44 324 45 45 47 46 Tons. 135 210 146 275 249 322 276 Manual movement only. Movement by band or hydraulio power. Manual movement exelusively. Hydraulic or hand power. » >) Hydraulie power only. »» J» In addition to the foregoing, there is a bascule bridge across the entrance to the Binnenhaven, the span of which is 75 feet and the width of platform 34 feet. The upper surface is perfectly horizontal, but the four girders, of which each leaf is composed, are curved in form, and find a lower bearing 8 feet below the roadway level. The arched structure, however, bas not been realised as designed. The union of the two extremities, in spite of several different devices successively tried, is not sufficiently perfect and each leaf remains a cantilever, exercising considérable force upon its axis, and causing a large annual expenditure for maintenance and repairs. The bridge is twin, comprising two separate structures side by side, each capable of acting without the other in case of repairs, but under normal conditions coupled together. The weight of each leaf is 121 tons, and gas engines supply the motive power. Bascule Bridges at Chicago.* These are of the type described as rolling bascules—one of the latest examples of which, near Taylor Street, Chicago, is illustrated in figs. 435 and 436—a design due to the late Mr. William Scherzer. The heels or shore ends are fitted with curved and counterweighted girders, which roll on a path on the bridge abutment, the girders having holes fitting over the teeth of a horizontal rack, which serves to guide the motion of the bridge. Each bridge has two leaves. The Van Buren Street bridge has a span of 115 feet between centres of bearings, and covers a waterway 109 feet wide. The structure is formed of three parallel trusses covered by a platform, comprising a roadway, 41 feet wide, and two footwalks, each 8 feet wide. The roadway accommo- dâtes a double track for electric trams. The North Halsted Street bridge has a span of 127 feet and covers a waterway 121 feet wide. There are only two trusses in this case, the roadway being only 34 feet wide, with two footwalks, 7 feet 3 inches wide. Provision is made for an electric railway. The railway bridge, between the two bridges just described, is con- structed on the same lines. The span is 114 feet, and the channel width 108 feet. The bridge is composed of two similar or duplicate pairs of leaves * Vide Engineer, November 26, 1897.