Landmark mixed-use tower built on a platform of structural steel floating over an historic building. This project involved creating a very complex steel structure built atop a series of large diameter pipe intersection columns to support a concrete office tower. A key feature of the building is innovative 10 ton structural steel castings which connect eight structural columns to each other to create what have been dubbed “Delta Frames.” These frames soar seven storeys in height to create an elegant atrium space and they also provide the structural support for a further 11 storey concrete structure.
Walters Inc. provided design assist services for the delta frames and tabletop, and detailed, fabricated and erected the structural steel. Walters worked closely with other project players during construction to coordinate all of the interface details to ensure the work came together and met the required structural tolerances.
In order to provide support for an office tower without cluttering the ground level atrium with columns, we developed a unique “Delta Frame” structure; structural steel columns, angled such that they meet halfway between floor and ceiling. This unusual configuration provided sufficient structural strength for us to slim the columns, providing a more airy and elegant space.
We recommended the central node and the upper and lower legs be created separately and assembled on site. We planned the design to expedite construction and minimize road closure times.
The column legs were tapered, shrinking from a metre to half a metre in diameter over a length of less than four metres. Walters designed and installed steel alignment frames that ensured precision to a quarter of an inch of what had been planned for the seven-storey base.
Walters design assist contributions resulted in optimally sized structural steel castings and minimized structural eccentricities within the critical structural connections. These geometric adjustments significantly reduced the bending loads on the legs and castings resulting in significant cost savings to the project.
The delta frame structural concept is an innovative approach to elevate new construction above refurbished existing buildings. We see this trend continuing as cities continue to revitalize old industrial neighbourhoods and further their goals for urban densification.
This project confirms that structural steel and steel castings offer limitless possibilities when faced with challenging project sites, existing builds and lofty goals.
It was essential for the success of this project that the structural steel contractor be brought in early as a design assist partner. Walters practical advice and ongoing budget feedback enabled timely decision making on how to proceed with the project.