Industrial History: 1919 Quebec Bridge over St. Lawrence River

It is a cantilever bridge with a suspended span. As is typical now, the suspended span for the 1916 design was built on shore, floated out into position, and then jacked up into position. Unfortunately, in 1907 the south tower collapsed during construction. In 1916, the suspension span fell while being hoisted into position. In 1917 they successfully completed the bridge.

Popular Mechanics, Dec. 1917, Public Domain

Bridges Now and Then posted
The center span of the Quebec Bridge being prepared to float into position for lifting into place, 1916-17. (Le Histoire du Rail)

Jeff Picka posted
The Quebec Bridge, originally built to carry three tracks of the National Transcontinental RR across the St Lawrence River just upsteam of Quebec QC. It still carries Via Rail trains running from Montreal to the Gare de Palais in Quebec along with three lanes of highway.
Brady Halligan: Remains the easternmost crossing of the St. Lawrence River and the longest cantilevered span in the world.

DNE 31 Flickr
PONT DE QUEBEC RAIL BRIDGE QUEBEC, QC

Engineering Community posted

By August 1907 the lower compression chords of the Quebec Bridge, the members carrying the whole cantilever, were bending in plain sight, one of them 57 millimeters out of line. Ironworkers saw it and stopped coming to work. Foreman E.R. Kinloch shut the site down. Management restarted it, unwilling to lose the crew and the rest of the building year.

The steel was answering for decisions made years earlier. Theodore Cooper, one of America's most celebrated bridge engineers, had stretched the main span from 490 meters to 549 to save money on piers, chasing the longest cantilever ever attempted.

In a cantilever, the dead load is mostly the steel's own weight: a longer span needs more steel, which adds weight, which needs more steel again. That heavier structure was never properly recalculated. And the specifications Cooper had written let the steel be stressed past normal limits. He underestimated the load and raised the stress ceiling at once. The margin was gone before the first beam went up.

On August 29, inspector Norman McLure carried the measurements to Cooper in New York, and Cooper finally accepted what they meant. At 12:16 PM he wired the builder to add no more load. It reached their offices at 1:15, and never reached the bridge. Near 5:30, the chords buckled, and the south arm dropped into the St. Lawrence in 15 seconds.

Of 86 men on it, 75 died. Thirty-three were Mohawk ironworkers from Kahnawà:ke, which lost a generation of its high-steel men in one afternoon.

The Royal Commission called it errors in judgment by Cooper and by Peter Szlapka, who designed the failed chords, and faulted the owners for putting no experienced chief engineer on site.

Nobody was prosecuted. Rebuilt heavier, the bridge fell again in 1916, killing 13 more, and was finished in 1917. It still holds the record Cooper reached for.

In Canada, this disaster became part of why the profession created the Iron Ring in 1925, worn as a reminder of an engineer's obligations. Despite the popular story, the rings are not forged from the bridge. They are iron or stainless steel. The obligation is what lasts.

On ROEBLING, our structures line, this completes a thought. Brooklyn's margin absorbed a crime. Bazalgette's margin bought 160 years. Quebec is what remains when the margin is spent in the design office: shannon.engineeringcommunity.net

John Kostelac commented on the above post
A view of the Pont De Quebec from my backyard.

<TCE>

[The following information until </TCE>, is from TheCanadianEncyclopedia (TCE)]
In 1907 it would be the largest structure of its kind and the longest bridge in the world, outstripping the famous Firth of Forth Bridge in Scotland. It carried trains, cars, and pedestrians. (It is still the longest cantilever bridge. [Wikipedia])

The spans of the 1907 design by Theodore Cooper were increased from 490m to 550m to reduce the construction cost of the piers. A Canadian government engineer reviewed the design and criticized the very high stresses caused by the longer spans. But Cooper blew him off. And Cooper refused to supervise the construction on site.

A young engineer by the name of Norman McLure was the first to see the problem. On August 6 McLure reported to Cooper that the lower chords on the south arm were bent. Cooper wired back almost plaintively "How did that happen?" McLure reported two more bent chords on August 12 but Chief Engineer John Deans insisted that work continue. On August 27 McLure measured the bend again. The deflection had grown. He informed Cooper who wired the bridge company in Pennsylvania: "Place no more load on Quebec bridge until all facts considered." Cooper assumed that the work had stopped. Deans had read his wire but ignored it.

The bridge collapsed on Aug 29, 1907 killing 75 of the 86 workers. "A group of sightseers looked back in horror when they heard the sound, for they had only left the bridge minutes before."

TCE

The Royal Commission of Inquiry investigating the calamity excoriated John Deans for his poor judgment in allowing work to continue when it was obvious that the bridge was in danger. The brunt of the blame, however, was placed on the shoulders of Theodore Cooper, who had committed grave errors in design and his calculation of loads. There was criticism of the bridge company for putting profit above safety and for engineers who neglected their professional and moral duties.

It took two years just to clean up the mess. The Canadian government assumed control and rebuilt it with much heavier (and uglier) cantilever arms. On Sept. 11, 1916, 13 men were killed when the span fell while being hoisted into position. It was finally completed in 1917.
</TCE>

To keep the bridge cheap, Cooper had already used unusually high allowable stresses in his initial design. And he did not recalculate the stresses when the span was lengthened! [ASCE]

McCord Museum

This image indicates that the first design built the suspended span in place.

Cleveland Statue University
[This is a much more technical article if you want more detail about the first design and its failure.]

The upper cords are in tension while the lower cords are in compression. Steel is strong in tension. It is a challenge to design truss members to handle compression. That is why it was the lower cords that first buckled.

In contrast to the 1907 failure, the only info I can find on the 1916 failure is "a problem with the hoisting devices." [Wikipedia]

By historical archive, Link, cropped

These two Facebook videos were my motivation for writing this post: moving the suspension span and 1928 usage and maintenance of the bridge.

Historic Bridges says that we can look forward to a third collapse because the Canadian National Railroad considers painting to be an aesthetic consideration rather than needed maintenance! ("
demolition by neglect " ) Evidently they have allowed the rust to get rather thick. Now there is the expense of removing the rust before it can be painted. Government entities have even offered to pay half of the cost, but CN still refuses to maintain the bridge.

Mike Brady posted six photos with the comment: "In 1917 it was completed, Quebec bridge. these photos show where it all comes together for movement of the structure. Bridge bearings of extra large size. This is one I would Like to see."

Mike Brady posted six images with the comment:

Found this to be interesting, compression members by comparison to each other of the largest Cantilever r/r bridges. From a engineering record magazine, 1913, look at the size of the new Quebec bridge beside the old one that failed.

Mike Brady commented on a post
Original bearing shoe, on first bridge

Québec en Vacances posted

There are those winter mornings where you'd rather stay comfortably lying warm, in the comfort of blankets. 

But the adage says that the future belongs to those who rise early so let's reinvent the world together! 

To Infinity And Beyond ! - Buzz Lightyears 

Mike Appleby: This bridge collapsed twice during construction, leading to 88 deaths.
Québec en Vacances: Mike Appleby Unfortunately true, during construction. But it still stands strong since 1919 as the longest canti-lever bridge in the world among the marvels of civil engineering.

Bridges Now and Then shared
Quebec Bridge