1. Bridge disasters

2. The Quebec Bridge Collapse August 29, 1907
Designed to cross the St. Lawrence River in the late 1800’s
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

3. Original Design:
Cantilever superstructure with two main supports placed 1600 feet apart
Weighing a total of 62 million pounds
Cooper said that this would be the best and cheapest plan and proposal

4. A Change in Plans
Before construction was to begin Cooper lengthened the span from 1600 ft to 1800 ft
There were no preliminary tests or research studies conducted to check these design changes
But the designer, Cooper, was sick and unable to visit the site while much of the work was in progress

5. 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!!

6. The Collapse: August 29, 1907

7. 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
Cooper’s career ended, and as a result he retired from public life.

8. The Schoharie Bridge Collapse

10. Layout 4 piers (Shallow Foundations)
5 spans (100, 110, 120, 110 and 100 feet)
112.5 ft wide bridge deck

11. Bridge Timeline
February 11, Construction company awarded contract
October, Bridge Construction complete
October 16, year flood occurs
Spring, Repair to plinths, bearings out of plumb, settled approach slabs, poor pavement support material and poor drainage
April 5, year flood, causing pier 3 collapse
April 11, 1987 – Mill Point Bridge collapses 3 miles upstream

13. Results of Collapse Five vehicles plunged into the creek below
One semi and one car on bridge during collapse
Three other vehicles could not stop in time
Nine bodies were pulled from the creek
One was never found

14. What Happened?
After the year flood, the riprap was no longer there
Years of scour continually eroded the bridge’s foundation soil
Pier 3 collapsed into a scour hole of approximately 9 feet in depth
No proper foundation inspections were made
Although, it was scheduled for inspection in 1987

15. What Could Have Been Done?
Adequate design for flood conditions
Pier 3 foundation was on erodable soil
Sheet piles left in place
Proper riprap use and placement
Used (50% heavier than 300 pounds)
Required (50% heavier than 1000 to 1500 pounds)
Proper maintenance

17. Quick Facts National Bridge Inventory Database
1 in 25 bridges is scour critical
Over 503,000 bridges
Between 1951 and 1988, 494 bridges collapsed due to similar conditions