Construction Approach, Challenges & Commitment to Quality
The truss bridge was fabricated by Supreme Steel in their shop in Northeast Portland. Materials incorporated in the construction included galvanized steel, weathering steel, a fiberglass decking system, and a stainless-steel mesh protection barrier that was manufactured in Germany. The entire building team took great pride in crafting the bridge with the highest level of workmanship. During fabrication, careful attention was paid to the quality of each individual weld, which was subject to regular inspection by multiple entities. The engineering and fabrication team utilized Revit extensively to detail and evaluate each of the complicated node connections on the truss. A detailed quality assurance and quality control process was also followed to ensure the painted members of the bridge were coated without flaw to stand the test of time.
While fabrication was wrapping up at Supreme Steel’s warehouse, work was underway at the site on West Burnside to prepare for the highly complex delivery of the bridge. Concrete abutments were placed on the steep hillside both north and south of Burnside. The south slope’s sharp grade required crews to create a temporary path in order to gain access to drill and install rock anchors. Due to the pristine environment surrounding the site, decommissioning this access path was done with extreme caution in order to preserve the natural setting.
Once fabrication of the bridge was complete at the warehouse, the 180-foot structure was cut into three sections, weighing 5.5 tons, 8 tons and 10 tons each, and transported to the site on individual semi-trucks over a span of five days. This transport was highly complex and required exhaustive pre-planning to ensure a safe and successful arrival at the site.
One of the primary challenges was access to the site. Navigating the large loads through downtown Portland was deemed highly challenging, so the only other option was to access the site via SW Barnes Road, through the historic 230-foot long Burnside Tunnel. Exhaustive pre-engineering of this transport revealed that the load would fit through this tunnel with a tight margin of 12-inches of space on either side of the load. Crews determined this was the best option and moved forward with planning for the bridge’s long, slow journey from NE Portland to the site via I-205 South to I-5 North to Highway 217 to Barnes Road. This transport was done in the pre-dawn hours and required intermittent traffic control on West Barnes and Burnside during the delivery.
While the first section of the bridge was installed, the other two pieces were welded together on the side of West Burnside. This work was performed in the tight staging area next to the road and within the east bound lane that remained closed for a limited time during erection. A challenging 8-hour crane pick was performed to lift and swing the second and third sections, over ¾ of the total bridge length, and marry the pieces together to unite the bridge.
The north abutment of the bridge includes a pre-cast artistic display that serves as the Donors Circle. In appreciation for those that contributed significant funds to the project, donors were honored with two-tone etched pavers placed in a circle formation at both entrances of the bridge. In order to achieve sharp and clear lettering, extensive mock-ups of the etched pavers were performed to ensure clarity for all letters and serves as another example of the project team’s commitment to quality.