Collaborating with the architect, FitzGerald Associates Architects, WSP designed a structure that provided the performance required with minimal impact to room layouts and the façade. The design included sufficient stiffness for motion-perception comfort in the top penthouse unit under predicted wind storms.
“At the upper levels, the shear walls were set along demising walls between units so as not to encroach in the units themselves,” Arjona said. “On the parking garage podium at the lower levels, many of those walls drop off to allow for the parking ramp to pass through.”
As a building with such an unusual design, it brought with it some challenges, both anticipated and unexpected.
The building’s elliptical floor plate required an approach that differed from traditional rectangular, straight-sided floors. Understandably, this presented a challenge in laying out the post-tensioned cables, which typically run at right angles to one another and the slab edge.
“We worked with the general contractor and the post-tensioned cable supplier to develop details where the post-tensioned tendons hit the slab edge at varying angles using stock, angled pocket formers rather than custom pieces to minimize cost,” Arjona said. “The post-tensioned design was highly efficient, requiring minimal reinforcement thanks for early collaboration with the architect and studies to set optimal column spacing coordinated with the unit layouts.”
He anticipates that this project will serve as a good standard of how post-tensioning can be used for curved floor plates. “WSP developed a scheme that was highly efficient and allowed the contractor to maintain its aggressive three-day pour cycles on the tower floors.”