Dangerous Designs:

Bridges are import means of commute over rivers, roads and valleys. There are hundreds of bridges in the world; some having very complex designs while others has simple architecture. It is a big responsibility for a designer of a bridge to make a design that doesn’t have any flaw in it.

A bridge collapsing due to bad judgment or design flaws becomes a source of much embarrassment as it is treated as major news. OnAugust 29, 1907 a canter bridge near Quebec City, Canadacollapsed resulting in the untimely death of around 75 people.

The Quebec Bridge of Canada, was built to connect south shore of the St. Lawrence river in Levis to the north shore at Quebec city. The bridge construction was started in 1903, it was almost completed in 1907.

The Head Engineer of the project was Theodore Cooper who was one of the most respected bridge builders at the time.

Original design of the bridge consisted of a superstructure weighing a total of 62 million pounds with two main supports placed 1600 feet apart. This design was modified before construction was to begin and the distance of two main supports was increased from 1600 ft to 1800 ft. The designer also altered the specifications in a way that would allow for higher unit stresses.

These design changes were made with out conducting any preliminary tests or research studies.

Finally when the construction started in 1904 the designer due to health issues was only able to visit the site three times. An unqualified person Edward Hoare was made the responsible engineer at the site.

During the construction some problems were observed but downplayed; like the actual weight of steel put into the bridge had far exceeded the planned weight, and compressive chords of the south cantilever arm were bent. It was also noticed that the deflection in another chord increased from three-quarters of an inch out of line to two and one-quarter inches in just a week’s time, but construction wasn’t stopped.

The reasons for failure were inaccurate theoretical estimates and unchecked changes to the design. The Royal Commission conducted an enquiry in to the collapse and attributed the failure to defective design and errors in the judgment of the designer. This practically ended Theodore Cooper’s career as he announced his retirement.

Image taken from Google Images.

Image taken from Google Images.