Introduction:
In 1907 Quebec was building the biggest cantilever bridge in the world, but little did
they know that on August 29 that they would also experience one of the largest bridge
collapses in history.
The bridge was to cross the St. Lawrence River, six miles above Quebec City. It was
the brainchild of the Quebec Bridge Company (QBC), 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 (850 metre) bridge must
have an 1800 (550 metre) foot single span, almost 150 feet (45 metres) 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.
The path to failure:
In late 1903, P.L. Szlapaka of the Phoenix Bridge Company had laid out the initial
drawings of the bridge. 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 8 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 8 million pounds (3.6M Kg) was within engineering
tolerances, Cooper let the work continue. He wanted to be known as the designer of the
greatest bridge in the world, so this project would continue at all costs. 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.
The collapse of 1907:
On June 15, 1907 an inspecting engineer noted that two girders of the anchor were
misaligned by a quarter of an inch. Cooper called this “not a 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 obviously more bent than previous days. The engineers on site decided
to send McLure to New York to consult directly with Cooper. B. A. Yenser, a senior engineer
on site for Phoenix, 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
workers.
The collapse of 1916:
After a Royal Commission of Inquiry into the collapse, construction started on a
second bridge. Three engineers were appointed: H.E. Vautelet, a former engineer for the
Canadian Pacific Railways, Maurice Fitzmaurice from Britain, who worked on the
construction of the Forth Bridge, and Ralph Modjeski.
Modjeski was a Poland-born United States engineer who achieved prominence as a preeminent bridge designer in the United States. Vautelet grew up in Chicago and was
President and Chief Engineer. The new design was still for a bridge with a single long
cantilever span, but a much more massive one. On September 11, 1916, the construction of
the bridge would be given another blow. This time, guide wires lifting the centre span into
place gave way, resulting in the span’s 150-foot plunge into the river below.
This second failure came at a cost of 13 human lives and, while this could not as readily be
blamed as an engineer’s carelessness or poor judgment, it forever added to the history of
the Quebec Bridge.
The completed structure:
The bridge construction was 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 Collapse. The bridge still stands today and still supports three highway lanes, one rail
line and one pedestrian footpath.