Sat. Apr 20th, 2024

The pillars of well-protected bridges in Quebec

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A container ship entered collided with one of the pillars of the Francis Scott Key Bridge in Baltimore overnight Monday to Tuesday, causing the structure to collapse.

Radio-Canada

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The collapse of Francis Scott Key Bridge, in Baltimore, which occurred after a container ship hit a pillar of the structure during the night from Monday to Tuesday, is unlikely to occur in Quebec where the bridges are well protected, according to specialists consulted by Radio-Canada.

In the province, freight ships cross half a dozen bridges between the cities of Quebec and Montreal. However, their pillars are protected, whether through riprap or bollards designed to avoid the catastrophic consequences of a collision as destructive as the one in Baltimore.

It struck me when looking at the images of Baltimore, the few structures to protect the pillars of the bridge. That the bow of the ship could come into direct contact with the pillar was what surprised me the most. The bridge did not seem adequately protected, says the president of the Corporation of Saint-Laurent Central Pilots, Pascal Desrochers, in an interview with ICI RDI.

The latter points out that the bridge most similar to that of Baltimore is the Laviolette bridge, between Trois-Rivières and Bécancour. Both are steel arch bridges.

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A complete riprap of the Laviolette Bridge is unnecessary, because a drifting vessel would run aground before hitting the ends of the bridge, due to the shallow depth of the water at this location.

In the 1970s, studies identified it as a very fragile structure. […] On the other hand, the pillars of the bridge were filled with rock in the 1980s to avoid collisions with ships.

A quote from Pascal Desrochers, president of the Corporation of Pilots of the Saint-Laurent Central

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In Quebec, the pillars of the bridges are on the shore, very far from the channel of navigation, while in Montreal, ships circulate in the seaway and therefore cannot deviate from their trajectory. Approximately 6,000 vessels transit the St. Lawrence River each year in the Central St. Lawrence Pilot Area.

Only the Jacques-Cartier Bridge, between Montreal and Longueuil, is an exception, but the volume of the pillars, the reduced navigation speeds (around 6 knots) and the more modest size of the ships mean that the impact force does not ;would have no common measure with what happened in Baltimore, according to Pascal Desrochers.

Furthermore, around the only pillar of the Jacques-Cartier Bridge submerged in water, the depth of the river is relatively shallow and a large ship would likely run aground before hitting the pillar.

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In the Jacques-Cartier Bridge sector, reduced navigation speeds, in particular, would reduce the force of impact.

The container ship Dali, which collided with Baltimore's Francis Scott Key Bridge at 1:30 a.m. Monday night, measured 1,000 feet long, 150 feet wide, and could carry up to 16,000 tons of cargo.

Bruno Massicotte, professor in the Department of Civil, Geological and Mining Engineering at Polytechnique Montréal, also notes that the Baltimore bridge seemed to lack protection around its pillars. In an interview, he emphasizes that in Canada as in the United States, federal laws govern maritime requirements. Afterwards, he adds, it is up to the owner of the bridge to meet these requirements.

Why the riprap was not done on a route as busy as the Baltimore Bridge? This is a good question, added the professor, mentioning that, according to him, it is a problem of prevention which has not been taken strictly enough.

At the time of publishing, six people were missing in the Patapsco River which runs alongside the Maryland metropolis.

With information from Mathieu Papillon and Éric Plouffe

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