Compare the Alex Fraser bridge.
On the new Port Mann, the bridge decks, east and west bound, are shrouded to the outer edges by cables carried from the centre towers. On the Alex Fraser, the cables are on the outside of the bridge deck.
Failure to deal with the predictable ice falls was a serious error. The entirely predictable difficulty was known to bridge design engineers. An Ohio facility had similar problems.
Ice prompts review, ToledoBlade.com, December 13, 2007
“The possibility of ice falling from the Veterans’ Glass City Skyway’s stay cables after winter storms was considered during the bridge’s design but deemed unlikely to occur often enough to justify countermeasures, an Ohio Department of Transportation spokesman said yesterday.
“Now state officials will have to decide if this week’s weather sequence – an ice storm followed a day later by steady rain that sent chunks of ice plunging onto the bridge’s southbound lanes – is as fluky as they thought.
“…The falling ice prompted officials to close two of the three lanes for about six hours Tuesday and was a contributing factor in a collision on the span…”
The engineering school at Dartmouth has a worthwhile webpage offering one possible solution, De-icing the world
“Dartmouth Engineering Professor Victor Petrenko and his research team discovered that applying short pulses of electricity directly to an ice-material interface produces some novel and desirable effects. This discovery led them to invent an ultra-fast and efficient method of ice removal and prevention called pulse electro-thermal de-icing (PETD).
“…Petrenko’s PETD method was also put to the test in Sweden where a 1712-meter-long ‘cable stayed’ bridge is experiencing major problems with icing. The $250 million publicly-funded bridge currently must be closed down for significant periods of time during the winter months due to dangerous chunks of ice falling at random off the towers and cables from heights of up to 140 meters.
“The first tests of PETD on a few cables and one pylon demonstrated instant de-icing action at very low energy consumption as compared with conventional de-icers.”
Wondering about the high cost of the new Port Mann bridge? Read Talking real money here at Northern Insight.