Day: July 17, 2020

O CANADA: Overweight span
O Canada

O CANADA: Overweight span

Overweight span When they started building the Pont de Québec spanning the Saint Lawrence River in 1905, there was a sense of pride. Designed mainly for rail traffic, it was going to be the biggest cantilever bridge in the world, longer than the Forth Bridge in Scotland. But on Aug. 29, 1907, a riveter noticed that a rivet he’d put in only an hour earlier had broken in half. Minutes later the structure twisted and collapsed with such force that people in Quebec City, 10 kilometres away, thought it was an earthquake. The engineering challenges of the Quebec Bridge had been daunting. It spanned a shipping lane, so it had to have a 45-metre clearance for ocean-going ships. It was 850 metres long, but needed a single 550-metre span in the centre. Key to its structural integrity was the ...
ARTIFACTS: Cool idea?
Artifacts

ARTIFACTS: Cool idea?

Aircraft carriers were a great innovation in protecting convoys out of range of land airbases during the Second World War. But aluminum and steel were in great demand. Could another material be used? Geoffrey Pyke, a researcher with Britain’s Combined Operations Headquarters, knew how difficult it is to destroy an iceberg, and he wondered: what about an airfield on the levelled top of a berg? Problem was that only about 10 per cent of an iceberg is above the surface, so one large enough to accommodate a runway would need hundreds of metres of ice below water and be impossible to tow. Besides, icebergs have a tendency to melt in mid-Atlantic. Enter pykrete, a mixture of water and wood pulp which proved amazingly strong after freezing. Invented by polymer chemists but named for Pyke...

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