A Skewed Plan Prompts Structural Innovations: TELUS Sky, Calgary
Session: Track D: Structural Engineering Award: Part 2 & Innovation Award, Part 1
Principal, Glotman Simpson Consulting Engineers
TELUS Sky is a mixed-use tower located in downtown Calgary that required a seamless structural unity between the two occupancies, while maintaining functional spaces for each typology. As the building rises, the façade steps back on opposing sides to form a skewed floor plan maximizing the glazed façade at the residential levels, without compromising the column-free office spaces below. The massing of the building necessitated a parametric load-bearing structure that follows the curving lines of the façade, which also produced significant unbalanced forces. The radially symmetric massing and parametric columns induce a dramatic torsional force on the building, which dictated a robust core structure. Two lateral load-resisting systems were utilized and stacked above each other to resolve the permanent gravity leaning and prevalent wind loads on the broad faces of the building. Below grade, the mat foundation rests below one of the deepest excavations in the city.
The effective depth of the lateral force-resisting system is maximized in the slender upper half of the tower, by introducing a wing-wall system in lieu of a conventional central core system. By engaging the full depth of the building, the stiffness of the system was optimized, thereby reducing the wind load demands due to vortex shedding. This, coupled with the continuous load path of a uniform column grid up the full height of the tower, maximized the outrigger stiffness of the system.
Below the outrigger system, within the office space, the coupled-core wall system increases the torsional resistance where the torsional forces induced by the walking columns are the greatest. The continuity of the load-bearing columns limited costly load transfer structure to only a few locations were dictated by the massing of the building.