File:Revision of the Niagara Railway Arch Bridge (1920) (14782709672).jpg

Identifier: revisionofniagar00char (find matches)
Title: Revision of the Niagara Railway Arch Bridge
Year: 1920 (1920s)
Authors: Charles Evan Fowler
Subjects: Bridges
Publisher: (New York) : American Society of Civil Engineers
Contributing Library: Brock University
Digitizing Sponsor: Brock University - University of Toronto Libraries

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esses forvarious members, in the locations fixed for the trains. The shortertrains consisted of one locomotive and four cars; the second of onelocomotive and seven cars; the third of two locomotives and sevencars; the fourth of one locomotive and sixteen cars; and the longestof two locomotives with fourteen cars. The locomotives ranged inweight from 177 tons and 61 ft. 5 in. long, to 220.9 tons and 72 ft.3 in. long. The heaviest locomotive likely to cross the arch is shownin Fig. 9. The cars were mainly steel hopper-bottom gondolas, 33 ft. 6 in. long, weighing empty about 18 tons, and loaded about 70 tons.There were a few larger cars, 42 ft. 6 in. long, weighing empty about26 tons, and loaded about 100 tons. The trains used during the entiretwo months, however, were of an extremely uniform character, thustending to great uniformity in the strain-gauge readings and increasedaccuracy.. Practically no change was found in the strain-gauge read- 1042 REVISION OF NIAGARA RAILWAY ARCH BRIDGE
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REVISION OF NIAGARA KAILWAY ARCH BRIDGE 1943 ings on the arch members whether thefirst, second, or third driver was locatedat a panel point. Strain Gauges. The greater part of the work ofmeasuring stresses was done by the useof the well-known Berry strain gauge,using the 8-in. gauge for secondarystress work, and the 20-in. gauge forprimary stresses. These instruments (Fig.10) have the side strips made of Invarmetal, the coefficient of expansion ofwhich is only about one-twenty-eighththat of carbon steel, and the handlingduring use does not seriously affect theaccuracy of the readings. One end hasa fixed conical steel point, and the otherend a movable conical steel point at-tached to a bell-crank lever. The longarm of this is attached to the spindleof an Ames gauge dial, and the leverhas a multiplication of five times, so thatwhile readings are made directly to0.0002 in., they may be estimated to0.00002 in. All the instruments were carefullycalibrated to determine their error, bythe us

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