Focus on Palliative Champlain Bridge

premier-treillis-acier-pesant-574For motorists, the Champlain Bridge maintenance works are first and foremost a puzzle. But extend the life of a deteriorated bridge as busy as the Champlain Bridge is a challenge which forced the engineers to be resourceful and develop new expertise.

On the occasion of the last blitz of the year work on concrete beams of the Champlain Bridge, La Presse was able to visit the scenes of the site that results in, this weekend, complete closure of the bridge towards Montreal until at 5 am tomorrow morning.

It is almost 7 pm on this Saturday morning when twenty workers are busy on deck. The crane operator takes one last look at the airspeed indicating that the winds do not exceed 25 km / h. The operation can proceed.

A first steel truss weighing 57.4 tons and measuring 75 meters long and 4 meters high, is lifted by two cranes installed on the bridge deck. The structure is then lowered under the bridge and installed below the concrete beams they reinforce. In all, four mesh must be installed in the day.

These trusses are supported by the headers, so that the load weight is distributed between the beam and the lattice. If the beam cracks, the mesh will then bear the whole load.

Due to the mild weather, the installation of a second truss began at 8 am. “This is the first time that we install in both simultaneously,” says François Demers, Senior Director of the Champlain Bridge project and the new bridge for the St. Lawrence. Around noon, the installation of the two networks was over.

When the building program comes to an end, by the end of 2017, all 100 edge beams (the beams at the ends of headers) has been reinforced by many lattice.

Although the bridge is in poor condition, Mr. Demers ensures that the batteries (the concrete structure that emerges from the water and on which the headers and beams are installed) are strong enough to withstand the 100 mesh over 57 tons each.

“We talk about palliative measures to extend the useful life of the bridge by the end of the new bridge in 2018,” but says Demers.

In 2015, 31 mesh were installed, counting the last four blitz. In 2015, this maintenance work will have cost 127 million.

A close watch on bridge

To ensure the safety of the bridge, the 100 edge beams are equipped with sensors connected to a data acquisition system whose establishment has just been completed. “It allows us to have live readings and see the state of the beams in real time,” says Demers.

We now know that all the edge beams is in a state of “advanced wear” says Demers.

“Some beams are worse than others, and in our trellis installation order, we give priority to those who are in a critical condition […], but there is no major rift in beam. ”
François Demers,
Senior Director of the Champlain Bridge project and the new bridge for the St. Lawrence
“In our edge beams, our tendons were sectioned with time due to corrosion and seepage. If a cable longer sectionnait, one would immediately alert would be sent to us, which was not possible before this system, “he adds.

Keeping alive the Champlain Bridge is a real feat, says Mr. Demers. “You start to lecture on structural maintenance at end of useful life. Wire mesh like this, there is nowhere else that is rather unique. So we are beginning to develop expertise. ”

This is probably one of the few positive chapter in the soap opera of the bridge whose design and construction were quickly made, badly made, at the lowest price, as well as a report showed the engineering firm Buckland & Taylor in 2013.

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