Physics don’t change, but engineering continues to make huge advances in construction. Recent work on a Highway 400 bridge showed how fast – and efficient – new tactics have begun.

Tackling work on existing bridges – especially those around a busy area – is often among the most difficult construction feats.

But now add the volume of traffic on Hwy. 400 into the mix.

Recently, as part of the Finch West Light Rail Transit (LRT) project, the team is using an innovative bridge construction method to replace the Highway 400 bridge at Finch Avenue West.

The ‘rapid bridge replacement’ method allows bridges to be replaced with minimum disruption to traffic. Instead of demolishing and removing the old decks alongside live traffic, the team reduces traffic impacts by first constructing the new decks on large steel scaffolding beside the highway.

The video shows Finch West LRT constructor, Mosaic Transit Group, receiving large reinforced precast concrete girders that build the framework for the bridge. The girders are then hoisted in place on scaffolding that has been set up beside Highway 400.

The girders will be used in the construction of two new bridge decks that will be constructed on the elevated scaffolding –so that when complete, they can be carefully moved into place. – Each of the new decks are 40-meters-long by 25-metres-wide and 15,000-tonnes on the scaffolding.

Once the new decks are ready, the crew will remove the existing ones from the substructure and install the new decks. The crew will work on one side of the bridge at a time, and plans to complete the installation in two weekends.

This innovative technique will help in reducing the number of traffic disruptions to motorists from years to a couple weekends and night lane closures.

Watch out later this spring for a new time-lapse video of crews removing the old bridge and installing the new one.