Glen Road Pedestrian Bridge

The Glen Road Pedestrian Bridge, a historic connection between Rosedale and St. James Town in Toronto, is undergoing a replacement. The new three-span frame bridge with inclined legs stands approximately 20m above Rosedale Valley Road and features a 4.8m wide multi-use pathway for active transport. The span arrangement is 30m - 40m - 30m. The bridge's superstructure is composed of three variable-depth steel plate girders supporting a concrete deck.

Erection Methodology: Pre-assembled segments were transported from the fabrication shop. These segments included the pier leg segment, consisting of two pier legs interconnected with bracings, and girder segments made up of three girder lines connected with diaphragms and plan bracings. The weight of these segments varied from 12 to 28 tonnes, totaling approximately 170 tonnes. A 600T crane, the DEMAG AC500-2 supplied by Mammoet, was used for the four-stage erection process. This crane was positioned on Rosedale road, roughly at the bridge's midpoint, and lifted segments from truck deliveries along the road.

Erection Sequence

Stage 1: The Pier Leg segments were installed and stabilized using a temporary shoring tower from Sarens. This tower had a hinge at the base and a hydraulic jacking mechanism at the top. It was pin-connected to the pier leg segment, allowing for vertical movement.

Stage 2: The Pier Table Girder segment was installed and joined with the Pier Leg segment. A survey was conducted, and adjustments were made to the temporary tower to achieve the desired angle/pitch for the drop-in segment fit-up.

Stage 3: The drop-in Center Girder Segment was installed, resulting in a stable structure or a 'coffee table'. After installing the minimum splice bolts and relieving the crane's load, the load in Sarens' tower was also relieved. Although the towers could theoretically be moved at this stage, the contractor decided to leave them in place and remove them later for logistical reasons. An analysis was conducted to ensure that the temporary towers, now supported by the permanent structure, were stable.

Stage 4: The abutment girder segments were installed to complete the steel skeleton. The geometry was assessed before and after the final bolt tensioning.

Challenges Addressed: During each phase of the structure's assembly, we evaluated its geometry and integrity. We also monitored control point elevations to align with the designer's intended girder elevations, ensuring the desired geometry and safety. We provided prompt, timely support on-site during the structure's assembly.

One significant challenge was the increased fit-up difficulty due to the structure being a frame, not a girder system. Restraint stresses occurred from fitting distorted components from fabrication tolerances and potential movements during the transport or handling of pre-assembled segments. We addressed these issues through detailed analysis, including possible restraining demands to verify the structure's integrity during assembly and thermal corrections to review the as-built geometry. Another challenge addressed through comprehensive analysis was development of the haunch profile. This was necessary to compensate for deviations in the structural steel's geometry and achieve the final deck grade.

Deck Pour Sequence: We developed a deck casting sequence and haunch profile to achieve the roadway finished grade. This process involved a detailed staged deck pour analysis to balance the geometric deviations of the structural steel girders from the target geometry. Using survey data provided by Eiffage, Spannovation conducted a staged construction analysis to simulate structural deformations from sequential deck pouring and concrete hardening. The most suitable pouring scenario was selected, with necessary adjustments to haunches, studs, and reinforcement to ensure post-deck pouring elevations aligned with intended finish grade elevations.