Erection of the Strathcona County Footbridge

The structural steel was recently erected for the Strathcona County Footbridge. This footbridge connects Edmonton and Strathcona County and links to the trail systems in the North Saskatchewan River Valley.

Girder erection was complex due to the S-curve plan geometry of the single trapezoidal box girder. It was erected over the North Saskatchewan River during river breakup. The girder erection and associated engineering were high-risk aspects of the project to ensure the structural steel could be safely and accurately erected. One of the critical stages involved a crane-assisted launch of the 130-tonne, 59m long spliced segment (S4 + S5) across the main river span and air splicing with the pier segments using a three crane operation.

Figure 1. Crane-assisted launch of the spliced segment (S4 + S5)

The erection process begins with the LTM 1500 (C2) supporting the east end of the spliced segment S4+S5 while a truck supports the west end and moves backwards. As the east end of the spliced segment S4+S5 gets within a 220ft radius of the LR 1400 (C3), approximately 14,200 from the edge of the berm, 50% of the load from the east end is transferred from the LTM 1500 (C2) to the LR 1400 (C3) using a load transfer triangle.

Figure 2. LTM rigged to segment east end through a Load Transfer Triangle

This process continues with the truck moving backwards while both cranes maneuver to share the load equally. As the east end of the spliced segment S4+S5 reaches within a 185ft radius of the LR 1400 (C3), about ~27m from the edge of the west berm, 100% of the load from the east end is transferred from the LTM 1500 (C2) to the LR 1400 (C3). Finally, the LTM 1500 (C2) is relieved from the east end of the spliced segment S4+S5 and the truck drives further backwards with the LR 1400 (C3) supporting the east end.

Figure 3. LTM 1500 and LR 1400 at start of the segment east end load transfer operation

When the east end of the spliced segment S4+S5 reaches within a 150ft radius of the LR 1400 (approximately 42m from the edge of the west berm), the LTM 1500 is connected with the west end. A tandem lift of the spliced segment S4+S5 is performed and the segment S4 splice end is aligned with segment S3 and air splice at field splice 3 is established while the cranes hold. After the air splicing is complete, the missing plan brace at the end along with all brace bolts are installed.

Figure 4. Tandem lift of the segment (S-curved geometry is visible)

Next, segment S6 is lifted with the ATF 400G and placed onto pier 2 temporary jacks, and the splice end is aligned with segment S5 and air splice at field splice 5 is established while the crane holds. After the air splicing is complete, the missing plan brace at the end along with all bolts are installed. All bolts are ensured to be snug tight and then the ATF 400G is relieved. At this stage, segments S4+S5+S6 were being supported by the LTM 1500 at the west end of S4, the LR 1400 at the east end of S5 and S6 is supported on pier 2. The cranes continued supporting the segment assembly S4+S5+S6 until segment S7 was installed.

Figure 5. Segment assembly (S4 + S5) and segment S6 erected and air spliced while the three cranes hold

Overcoming the challenges of this procedure required meticulous planning, coordination, and engineering. Significant project parties include:

Owner: Alberta Transportation

Designer: Associated Engineering

General Contractor: Graham

Fabricator: Canam

Erector: N-Force Crane & Equipment Ltd.

Construction Engineer: Spannovation Consulting