After months of waiting, the City of Edmonton believes it finally knows what caused massive steel girders on its 102 Avenue Bridge project to buckle.
The girders buckled March 16 while being installed. According to the city, a preliminary investigation suggests the buckling was the result of the subcontractor, responsible for installing the girders, misinterpreting the precise bracing requirements between the last four girders.
The spacing braces failed after the crane released the second to last girder, resulting in the buckling of three girders. Graham Group subcontracted the girder installation to a firm that has been involved with this type of work for more than 40 years. The city initially did not name the firm, but it was later revealed that Supreme Group was the subcontractor. They said the company is considered a leading Canadian subcontractor in this field.
The bridge structure for this project required a unique, project-specific procedure in order to lift and place the girders.
Laura McNabb, a spokesperson for the city, said Graham worked with the sub to develop the bracing requirements. The three girders were removed and have been repaired off-site using heat straightening.
The repaired girders passed all the required quality tests and inspections, and were accepted by the engineer of record for reinstallation.
The removed girders have since been reinstalled and the bridge structure has been approved and deemed safe for construction to resume.
All of the documentation on the repair work and ongoing construction has been reviewed by the contractor's engineering team, as well as third-party engineers and the city staff overseeing the project.
Ongoing construction for the project is now back to being managed by the engineer of record and city staff.
A construction acceleration plan has been developed and bridge work continues with extended hours and multiple shifts throughout this construction season.
McNabb explained that there will be minimum 17 hour shifts, seven days a week, depending on weather. The timeline remains consistent with the previous update, with the project scheduled to be complete in 2016.
The contractor could face heavy penalties. McNabb said that for every day that passes after the original project deadline — Sept. 30, 2015 — there is a penalty of $11,500.
McNabb said the buckling means that the project will not be completed until late summer or early fall 2016. She said the delays do not impact the city's budget for the project as the penalties are based on cost recovery.
The 102 Avenue Bridge over Groat Road serves as a major east/west corridor into and out of Edmonton's downtown. Constructed in 1910, the bridge reached the end of its lifespan and was demolished last year.
The replacement bridge has a clear span of about 100 metres and will maintain the existing four-lane configuration. It is designed to accommodate two 2.1 metre wide bike lanes on the road shoulder and 2.2 metre wide sidewalks along the north and south sides.
The design of the new bridge includes stabilization of both the east and west slopes using soil nails, concrete deck with asphalt surfacing and upgrades to the drainage infrastructure.