Gordie Howe International Bridge

By Mark Palmatier | March 12, 2024

Scaffold Design

As our northern neighbor, it should come as no surprise that Canada is one of the top trading partners with the United States. Over $664 BN of trade was conducted between Canada and the US in 2021, and nearly a quarter is moved on the Detroit River between the Canadian city of Windsor and Detroit, MI. It is for this reason that a plan for a new bridge linking the two gateway cities began. After more than a decade of planning and preparation, construction of the Gordie Howe International Bridge was started in 2018. Ultimately, the bridge would span over half a mile, with the iconic silhouette of the bridge being set by two A-shaped piers rising 722’ above the river.

 

D.H. Charles Engineering, in a wildly successful partnership with Universal Manufacturing, Inc., was awarded the 2023 Scaffold & Access industry Association (SAIA) Industrial Collaborative Project of the Year for engineering a unique scaffold stair access design that would provide access to the climbing concrete formwork used to pour the US Main Span bridge pier.

 

 

From the outset, the towering height that was needed proved to be a significant design aspect we would undertake. At nearly 550’-tall, just the weight of the scaffold components themselves in a continuous stair tower would exceed the scaffold strength, and that was before accounting for any sort of worker live load. Coupled with that was ensuring the stair towers were firmly secured to the pier structures. For a system that would be in place for multiple seasons and subject to some of the harshest environs, a rigid and robust tie system was essential.

 

The most evident design challenge as we began engineer the scaffold system was the shape of the pier itself. Due to the A‐frame shape, as the pier legs increased in height, they would also slope toward each other to eventually meet at the top. From a scaffold design perspective, this made for an increasingly complex layout and tie situation: as the scaffold got progressively taller, the structure to which the scaffold was tied to for laterally stability would continuously pull further and further away.

 

 

Ultimately, we determined a three-phase approach would provide the best balance. Phase 1 would consist of the base of the scaffold, set on the ground, and reach a maximum height of ~214’‐tall. At that point, a steel platform structure would be secured to the bridge pier upon which the Phase 2 stair tower would be set and stretch an additional 157’‐tall. A second steel platform would be anchored to the bridge structure nearly 371’ above the ground. Reset on this final platform, the Phase 3 stair would reach the final 173’ and allow access to the point where the two legs of the A‐frame would meet. For each stair tower resting on platforms, the base of the stair tower was shifted accordingly to address the slope of the pier.

 

Once the height and weight of the stairs were managed, the focus shifted to how the scaffold would be secured to the piers. Set on the banks of the Detroit River, and significantly taller than any structure around, there would be little relief from the harsh winds that can form in the region. This would be especially true for the tallest scaffold of Phase 3. Not only would it see the full force of wind speeds potentially topping 105 mph, but at the highest section the stair tower would be nearly 20’ away from the pier structure. This meant any bracing back to the pier would see intense asymmetric loading with tie lengths exceeding 25’ long. To ensure the forces that would be collected by the stair tower were accurately tallied, each phase of the stairs was reconstructed in a finite element analysis computer model and analyzed under various wind loading conditions. The models not only considered the height of each built stair section, but also the elevation and duration it would be installed. Because the tie lengths and angles varied at each tie location as the pier shifted in relation to the stairs, the bracing at each tie level was modeled, with a total of 26 models by project completion. This allowed us to confidently move forward with each phase of the design.

 

 

Both the expertise and ingenuity brought forth on this project made it a successful collaboration. This unique access solution was achieved using standard modular scaffold components because of the knowledge and experience that both Universal Manufacturing and D.H. Charles’ brought to the table.

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