The Quebec bridge
A bridge, a necessity
THE BROAD WATERS of the St.Lawrence Rive have long served Canada as a great artery of commerce, but after the coming of the railroad, the river also became a barrier to east-west transportation at the river's two principal Quebec ports. Montreal solved the problem in 1859 with the Victoria Bridge, leaving its downriver commercial rival, the city of Quebec, at a severe disadvantage. Quebec eagerly sought a bridge of its own. The best place for one was at a point 7 miles upstream from the Quebec Citadel, where the river norrowed to less than three-quaters of a mile in width, and flowed between high cliffs. But even at that it was a difficult challenge to the skills of bridge engineers and builders, with a maximum water depth of 190 feet and currents that flowed at close to 7 mph. There were several proposals for great suspension or cantilever bridges, but nothing came of them until formation of the Quebec Bridge Company in 1887.
Implementation
By 1900 the company had contracted with the Phoenix Bridge Company of Pennyslvania to build a cantilever bridge with a main span of 1800 feet that would have eclipsed Scotland's Firth of Forth bridge as the longest cantilever span in the world. By Summer 1907 the structure was well advanced, with the cantilever arms projected out from both shores of the river, when a disastrous failure of the south arm plunged 76 workmen to their deaths. A Royal Commission attributed the failure to defective design and errors in judgment by the engineers. Constraints
A year later the Canadian government appointed a board of engineers to try again, chief among them the noted American bridge designer Ralph Modjeski. The new bridge would have anchor arms of 515 feet, with cantilever arms extending 580 feet beyond the main piers and supporting a 640-foot suspended span, giving the bridge the same record-breaking 1800 foot clear span planned for the previous design. But this time the engineers proceeded with extreme caution. The bridge was designed to support much heavier loads than the earlier one had been, extensive tests of materials were made, and design calculations were checked and rechecked. Even though the designers used a newly developed nickel alloy steel that could safely support stresses 40 percent greater than could the carbon steel used in the earlier design, the critical lower chord members of the cantilevers arms were made several times larger and heavier than those of the failed bridge.
Fondations
Work began on the new bridge in 1909 and was nearing completion seven years later when
disaster struck again. The 5000-ton center span was being lifted into place when a bearing
failed, allowing the span to fall into the river. This time, 13 workers were killed. A year
later a new span was successfully lifted into place, and in October 1917 the first train crossed
the great bridge. The bridge has stood firmly astride the St.Lawrence ever since, helping to
link the Maritime Provinces and eastern Quebec with the rest of Canada. Now the property of
Canadian National Railway, the bridge carries some freight as well as VIA Rail Canada's
Quebec-Montreal passenger trains. The record its builders set in 1917 still stands, for the
Quebec Bridge remains the longest railroad cantilever span ever built.
A plaque has been erected which commemorates the bridge has an "International
historic civil engineering landmard"
Please note the date mistake (English vs French!)
1) William D. Middleton - TRAINS August 1996 p.43
2) Canadian Government Railways, Quebec, Que., 1917
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