TORONTO, ON

Highway 427 Over Highway 407 ETR

This project involved widening the Highway 427 mainline structures over Highway 407 ETR to accommodate new primary traffic and HOV lanes for Highway 427.

TRANSPORTATION

Two existing structures were widened on each side, for a total of four widenings.

In this location that would have resulted in the need to construct the new bridges at an elevated position and jack them down to the final grade, as there was no practical falsework solution under the new bridges. Any falsework would also result in long-term reduced lane widths for Highway 407 ETR, with a resulting reduction in service and increased traffic hazard.

The existing bridges were post-tensioned voided slab structures built in the early 1990s. The typical widening for this type of structure is a post-tensioned slab joined to the existing structure with a closure pour.

Critical considerations in the final design included the long-term creep and shrinkage, flexure in the existing concrete deck cantilevers, and differential temperatures between the existing concrete structures and new steel structures.

The project also included a widening of an existing rigid frame structure over an access ramp. Originally planned as an extension to the rigid frame in the Environmental Assessment, our team changed the structure to a prestressed concrete plank structure with a cast-in-place deck to eliminate falsework and minimize disturbance to the ramp.

In this location that would have resulted in the need to construct the new bridges at an elevated position and jack them down to the final grade, as there was no practical falsework solution under the new bridges. Any falsework would also result in long-term reduced lane widths for Highway 407 ETR, with a resulting reduction in service and increased traffic hazard.

Our team proposed and developed an alternate solution using heavy steel box girders to match the existing structure flexural properties as closely as the concrete option would have, while also avoiding falsework. This option reduced the long-term effects of concrete creep and shrinkage.