The Quebec Bridge Collapse August 29, 1907

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The Quebec Bridge CollapseAugust 29, 1907

• By Dan Ford

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Purpose for the bridge

• The St. Lawrence River became a barrier to
  east-west transportation
• Montreals success was appealing
• So in 1887, the Quebec Bridge Company was formed

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The Hired Help

• The Phoenix Bridge Company of Phoenixville,
  Pennsylvania was given the contract
• The Head Engineer of the project was Theodore
  Cooper
• One of the most respected bridge builders at the
  time

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The Original Design

• Cantilever superstructure with two main supports
  placed 1600 feet apart
• Weighed a total of 62 million pounds
• Cooper said that this would be the best and
  cheapest plan and proposal

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A Change in Plans

• Before construction was to begin Cooper
  lengthened the span from 1600 ft to 1800 ft
• He also modified specifications that would allow
  for higher unit stresses
• There was no preliminary tests or research
  studies conducted to check these design changes

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Construction

• Erection of the superstructure got underway in
  the summer of 1904
• Due to Coopers health issues he only visited the
  site of the bridge 3 times
• This left a lack of authority on the construction
  site

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Troubles During Construction

• The actual weight of steel put into the bridge
  had far exceeded the original weight
• compressive chords 7-L and 8-L of the south
  cantilever arm were bent
• On August 27, 1907, it was reported that the
  deflection in chord 9-L had increased from
  three-quarters of an inch out of line to two and
  one-quarter inches in just a weeks time
• Yet construction continued!!

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The Collapse August 29, 1907
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Reasons for failure

• Financial troubles with the Quebec Company
• - Inaccurate theoretical estimates of the
  bridge's weight
• - Unchecked changes i.e. Coopers high-regard

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The Aftermath

• Of the 86 men who were still on the bridge at the
  time of the collapse only 11 survived
• The Royal Commission attributed the failure to
  defective design and errors in the judgment of
  Theodore Cooper
• Coopers career ended, and as a result he retired
  from public life and died in his home on August
  24, 1919, at the age of eighty.

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The End