Bridge disasters The Quebec Bridge Collapse August 29

Bridge disasters

The Quebec Bridge Collapse August 29, 1907 l Designed to cross the St. Lawrence River in the late 1800’s The Phoenix Bridge Company of Phoenixville, Pennsylvania was given the contract l The Head Engineer of the project was Theodore Cooper - One of the most respected bridge builders at the time l

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

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

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

The Collapse: August 29, 1907

The Aftermath l Of the 86 men who were still on the bridge at the time of the collapse only 11 survived l The Royal Commission attributed the failure to defective design and errors in the judgment of Theodore Cooper l Cooper’s career ended, and as a result he retired from public life.

The Schoharie Bridge Collapse

Layout l 4 piers (Shallow Foundations) l 5 spans (100, 110, 120, 110 and 100 feet) l 112. 5 ft wide bridge deck

Bridge Timeline l l l February 11, 1953 - Construction company awarded contract October, 1954 - Bridge Construction complete October 16, 1955 - 100 -year flood occurs Spring, 1957 - Repair to plinths, bearings out of plumb, settled approach slabs, poor pavement support material and poor drainage April 5, 1987 - 50 -year flood, causing pier 3 collapse April 11, 1987 – Mill Point Bridge collapses 3 miles upstream

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

What Happened? After the 1955 100 -year flood, the riprap was no longer there l Years of scour continually eroded the bridge’s foundation soil l – Pier 3 collapsed into a scour hole of approximately 9 feet in depth l No proper foundation inspections were made – Although, it was scheduled for inspection in 1987

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

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