Original CN Tower engineer shares his thoughts on tower's 50th birthday
· Toronto Sun
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“(People) called us lunatics for trying to build something like this,” CN Tower structural engineer Franz Knoll told the Toronto Sun. “There were towers before it, but we built something a little bit higher than the tallest we had at the time.”
When the Austrian-born engineer came to Canada, he considered himself “lucky” to be hired by a consulting and engineering firm headed by architect R. R. Nicolet. In the early ’70s, Nicolet’s firm was approached by the Canadian National Railway wanting to show the strength of Canadian industry by building the tallest building in the world.
“I was very lucky to get into a project like that,” Knoll said Thursday. “At the time I was a fresh immigrant, and it worked out that I was blessed with this task.”
A structural engineer designs the framework, skeleton and foundation of buildings, bridges and other structures.
When the tower opens its doors on Friday, it will celebrate its 50th anniversary.
Never been done before
The principle members of the design and construction team were Ned (Edward) Baldwin, architect; Roger Nicolet, structural engineer; Franz Knoll, structural designer; Frank Tam, structural site engineer; Jules Petrinec, mechanical engineer; Jim Armstrong, electrical engineer; and Andre Jordan and Jack Whyte of Foundation Company of Canada, who were responsible for the construction.
The tower has been chosen by the American Society of Civil Engineers as one of the Seven Wonders of the Modern World. At 1,815.5 feet (553.33 metres) it was the world’s tallest tower, building and freestanding structure from 1976 until 2010. It is still the tallest building in the western hemisphere.
With a list of impressive bona fides from the day the exterior was finished until the day its doors opened to the public, Knoll was asked what he was most proud of.
“That we were able to complete it without any great problems,” he said. “There were problems on the way, of course, and with the technology that went into it at the time was, just to take it to stand up to something that had never been done before.”
Soft as concrete
Given the magnitude and the audacity of the job, there were mishaps along the way.
Construction crews poured concrete into a mold known as a slipform. As the concrete hardened, the slipform was tightened, shrunk, and then gradually raised, creating the tapered look of the tower.
“We did some testing for it, but it turned out on the first pour we lost some concrete as it fell out of the form, and we had to go back and start anew,” Knoll said. “It was soft. The concrete didn’t set quick enough.”
Construction began on Feb. 6, 1973, with 1,537 workers working five days a week. The work was finished on Feb. 22 the following year. The antenna portion was completed on Apr. 2, 1975. The cost was $63 million. The tower weighs 117,910 metric tonnes or 130,000 tons.
“This one was outstanding, and it was done in a climate of trust,” Knoll said. “All the main participants, I mean we could have been a source of contention, but it wasn’t. We were able to work together in a productive and friendly way without going to court. That is always a risk you take with large projects, as they end up in court because it is a money issue.”
FUN FACTS ABOUT THE CN TOWER
– Construction materials included 40,524 cubic metres, or 53,000 cubic yards, volume of concrete
– 998 km of post tension steel, 4,535 metric tonnes of reinforcing steel and 544.2 metric tonnes of structural steel
– 1,537 workers worked around the clock, five days a week, 24 hours a day to build the tower, with a final weight of 117,910 metric tonnes or 130,000 tons and a cost of $63 million
– T here are 1,776 stairs in the tower
– The total weight of the steel used on the edge walk is 46,875 kilograms or 105,000 pounds
– The Edge Walk was recognized by the Guiness Book of World Records as the world’s highest external walk on building