|In 1907 Quebec was building the biggest cantilever bridge
in the world. Little did they know that on August 29 that they
would also experience one of the largest bridge collapses in history.
The bridge across the St. Lawrence River, six mile above Quebec City,
was the brainchild of the Quebec Bridge Company, a group of local business
people. Until then goods were brought from the south shore to
Quebec City by ferry. In 1903 the QBC gave the job of designing of
the bridge to the Phoenix Bridge Company. They also contracted a renowned bridge builder from New
York by the name of Theodore Cooper to oversee
the engineering design and construction.
The peculiarities of the site made the design of the bridge a most
difficult one. Because the St. Lawrence was a shipping lane, the 2800
foot bridge must have an 1800 foot single span, almost 150 feet above the
water, to allow the ocean-going vessels to pass. Further, the
bridge was to be multifunctional and was required to be 67 feet wide to accommodate
2 railway tracks, two streetcar tracks and two roadways.
For those who are not familiar with a cantilever bridge design, think of
it as a continuous beam anchored at both ends to pillars. The key
to the bridge design was the weight of the centre span. This
cantilever design is also use in large building where interior pillars
cannot be used to support the
roof, such as aircraft hangers.
In late 1903, P.L. Szlapaka of the Phoenix Bridge Company, had laid out
the initial drawings of the bridge. After a few meeting, similar
to our modern day
conference calls, his design was approved with
very few changes by Cooper. The estimated weight of the span was
calculated based on these initial drawings. In 1905 the working
drawings were completed and the first steel girder was bolted into
place. These working
drawings took over seven months to reach
Cooper for final approval. In the meantime the work had begun. It
wasn't until Cooper received the drawing that he noticed that the
estimated weight of the span was off, on the low side, by almost eight
million pounds. Cooper had one of two choices: condemn the design
and start over; or take a risk that there would be no problem.
Telling himself that the eight million pounds was within engineering
tolerances, Cooper let the work continue. After all, he wanted to
be known as the designer of the greatest
bridge in the world. Also
factored into the decision was that fact the Prince of Wales (later to
be King George V) was scheduled to open the bridge in 1908 and any delay
in construction would upset the planning.
His was a fateful decision.
June 15, 1907 an inspecting engineer noted that two girders of the
anchor was misaligned by a quarter of an inch. Cooper called this a
"not serious" problem. In the inspection report in
August, 1907, it was noted that the girders had moved out alignment a bit
more and "appeared bent". Although this condition was a bit
more concerning, the work continued.
On August 27, 1907 the warning bells finally went off when the
inspection team headed by Norman McLure, noted that, over the weekend, the girders
had shifted a
"couple of inches" and were more obviously bent. The
engineers on site decided to send McLure to New York to consult
Cooper. B. A. Yenser, a senior engineer on site for Pheonix, agreed that
the problem was serious enough to warrant the trip. There was a
telephone at the construction site, but phoning Cooper was deemed not
wise because the phone was on a party line and the wrong ears might be
listening in. And they certainly did not want to alarm any one.
The next morning, with the engineering team off to New York, Yenser
took it upon himself to continue work. When asked why he restarted
the work considering the condition of the girders, he stated
that he "had a dream". In the dream he was told that the
girder problem was not serious. The team had not yet heard from
Cooper but the other senior engineers on site, for some reason, agreed with Yenser.
At 5:32 PM on the 29th of August, while McLure was making his way
back from New York, all hell broke loose at the construction site when
the girders trembled with a grinding noise and gave way. The
bridge structure plunged over 150 feet taking with it the lives of 75
The bridge construction was restarted in 1913 and completed in August
1919. Almost 12 years to day after the tragic day, the Prince of
Wales finally opened the memorial to the men lost in the Quebec Bridge