On December 3, 1917, after almost 20 years of planning and construction, the Quebec Bridge opened for traffic. A major engineering feat in its day, it still stands as one of the world's great bridges. Two major collapses during construction resulted in heavy loss of life. August 29, 1907

This exhibit, with parts taken from a book titled "The Quebec Bridge" by the St. Lawrence Bridge Company, is an attempt to preserve some of history of that great undertaking. (http://www.civeng.carleton.ca/Exhibits/Quebec_Bridge/intro.html/ July 2001, Carleton University, Ottawa, Ontario, CANADA) It took only fifteen seconds for the massive south arm of the Quebec Bridge to fall into the St. Lawrence River in 1907, but the prelude to the catastrophe began years before. -- by John Tarkov (Carlton University, Engineering Case Library report "ECL 270")

The Final 15 Seconds
At five-thirty on the afternoon of August 29, 1907, a steelworker named Ingwall Hall was perched high on the partially constructed south cantilever arm of the Quebec Bridge, a few miles from Quebec City. The bridge was to have a span of eighteen hundred feet when completed -- the longest in the world. The first whistle signaling the end of the workday had just blown, and Hall was waiting out the few minutes before the final whistle that would send the men on the structure home for the night.

Instead of the final whistle, the workers heard a loud report like a canon shot. Two compression chords in the south anchor arm of the bridge had failed, either by the rupture of their latticing or by the shearing of their lattice rivets, and as the distress of mortally tortured steel spread through the entire superstructure, the nineteen thousand tons of the south anchor and cantilever arms and the partially completed center span thundered down onto the banks of the St. Lawrence River and into the water the bridge had been designed to cross. One eyewitness likened the collapsing columns to "ice pillars whose ends were rapidly melting away".

Swallowing water and fighting the river's sudden turbulence, Hall had to struggle in order to breathe. After a few long minutes, a rescue boat reached Hall, and he was dragged aboard. He had lost two fingers, but of the eighty-six men on the bridge when it went down, he was one of only eleven who survived.

Prelude to Failure
No bridge collapses quickly. Just as the safe completion of a bridge is measured in years, the failure of a bridge can be reckoned in the same way. Though the chaotic physical dismemberment of the south arm of the Quebec Bridge took no more than fifteen seconds, the more orderly prelude to the catastrophe began long before.

It began in the summer of 1897, when the consulting engineer Theodore Cooper attended the annual convention of the American Society of Civil Engineers in Quebec City. A former director of the society, Cooper was one of the most respected bridge builders of the time. He made an excursion to the proposed site of the Quebec Bridge and within a week expressed an interest in giving the Quebec Bridge Company the benefit of his expertise.

Cooper's tender of interest was hardly unbidden. The Quebec Bridge Company had been sounding out American bridge engineers as consultants because its own chief engineer, Edward A. Hoare, had never worked on a bridge with a span longer than three hundred feet. Cooper was a proud, confident man, fiercely devoted to his calling. He had been graduated as a civil engineer from Rensselaer Institute (now Rensselaer Polytechnic) in 1858 at the age of nineteen. Enlisting in the Navy in 1861, he served as an assistant engineer of the gunboat Chocura for the last three years of the Civil War, then moved on to a teaching post at the United States Naval Academy. After a tour of duty in the South Pacific, he resigned from the Navy in July 1872. In May of that year, Capt. James Eads appointed Cooper the inspector of steel manufacturing for Ead's most important engineering work, the St. Louis Bridge.

The Quebec Bridge, viewed in that light, was irresistible to Cooper. He said the bridge would be his last work. It would stand as the crowning achievement to an elegant career.

Almost two years would go by before Cooper's affiliation with the Quebec Bridge Company became formal. The financially troubled company had a history of moving slowly -- or not at all.

Later Cooper would maintain that no pressure had been brought to bear on him. In any event, on June 23, 1899, he sent his findings to the Quebec Bridge Company. "I therefore hereby conclude and report," he wrote, "that the cantilever superstructure plan of the Phoenix Bridge Company is the 'best and cheapest' plan and proposal."

Those three words -- "best and cheapest" -- became a touchstone for Cooper in his approach to the bridge. His subsequent letters to Quebec and Phoenixville are seasoned with references to the fiscal consequences of major design decisions. None of the parties involved ever placed costs before safety outright, but their aim was clearly to build a bridge that could bear the twin loads of its own mechanical burden and the Quebec Bridge Company's financial burden.

Five days before his formal appointment on May 1, Cooper exercised his authority by recommending that the span of the bridge be lengthened from sixteen hundred feet to eighteen hundred feet. His explanation for this major design change revealed an attentiveness to both engineering and expense. Piers constructed in deeper water would be subject to the heavy ice floes of the main channel. Closer to shore, they would be less vulnerable -- any quicker to build, speeding up the completion of the entire work by at least one year. To keep down the increased cost of steel in the superstructure for an eighteen-hundred-foot span, Cooper recommended another major design change: modified specifications that would allow for higher unit stresses. [see Exhibit A1]

His recommendations were approved at Quebec almost as a matter of course. And then, for the next three years -- as work proceeded on the substructure, the anchorages, and the approach spans -- practically nothing was done to prepare for the engineering difficulties posed by the eighteen-hundred-foot span and the higher allowable stresses.

Three years of opportunity for deliberate preparation had been lost. In the rush to provide drawings so that the steel for the bridge could be fabricated with little loss of time, there was no recomputation of assumed weights for the bridge under the revised specifications. It was an oversight of critical importance, and Theodore Cooper did not intervene. He decided to accept the theoretical estimates of weight that the Phoenix Bridge Company had provided.

During the three languid years that preceded the project's lurch into progress, Cooper visited the site of the bridge three times.

Robert Douglas, an engineer in Schreiber's department, had reviewed Cooper's new specifications for the eighteen-hundred-foot-span bridge and had criticized the high unit stresses. "Considering that the American government in several cases appointed four or five engineers to consider and determine unit stresses of unexampled magnitude," Douglas would say later, "I thought that this matter was too important to be left to the judgment of Mr. Cooper." But confidence in Cooper was the byword just then, and foresight was at a premium.

Upon learning of Schreiber's proposal, Cooper wrote angrily to Quebec: "This puts me in the position of a subordinate, which I cannot accept." in 1905 he insisted that a young, recently graduated engineer be installed at Quebec to serve, in effect, as his eyes and ears on the bridge.

The young engineer's name was Norman McLure, and though nominally he answered to both Cooper and Hoare, he was in fact Cooper's personal representative, communicating with Cooper frequently. McLure's intelligence, energy, and loyalty suited Cooper well. He was well trained and well recommended, and had enough technical competence to keep Cooper accurately informed and to execute Cooper's instructions, but not nearly enough experience to act without Cooper's authority.

The practical effect of all this, after the contract between Quebec and Phoenix was signed and erection of the superstructure got under way late in the summer of 1904, was to leave the day-to-day, hands-on building of the most technically ambitious bridge project in the world to a group of men utterly unprepared to grasp the scope of the work. No one at the site knew enough about what he was doing to act with authority. Everything of import was referred to Cooper.

On February 1, 1906, they began to pay the price. Cooper received a report from E.L. Edwards, the Phoenix Bridge Company's inspector of materials, revealing that the actual weight of steel put into the bridge had far exceeded the original estimated weight. (By June the projected weight for the complete structure would have to be raised from sixty-two to seventy- three million pounds.) Cooper concluded that the increase in the already high stresses, due to the error reported by Edwards, was between 7 and 10 percent.

By this time the south anchor arm, tower, and two panels of the south cantilever arm had been fabricated, and six panels of the anchor arm were already in place. Cooper decided that the increase in stresses was safe, and he permitted work to continue. The only alternative would have been to start building the bridge all over again.