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The architectural design of Optima North Plaza’s 28-story office tower shifted portions of the tower floor plates to create large cantilevered floors and terraces. To support the architectural form, the structural design incorporated concrete slabs cantilevered 15 to 21 feet from the supporting column line.
RRJ was retained to conduct an initial peer review of the formwork and cantilevered steel shoring systems to address concerns of safety and adequacy of the formwork to maintain concrete construction and curtainwall installation tolerances.
RRJ also performed a Finite Element Model (FEM) analysis incorporating the stiffnesses of the shoring systems and the concrete frame to more accurately estimate the load distribution and formwork deflections.
The FEM analysis predicted deflections much larger than the original shoring calculations, exceeding the American Concrete Institute placement tolerances. In response, the formwork elevation at the end of the cantilever was elevated (cambered) to address the anticipated deflection of the shoring system. A series of surveys further validated the FEM model results and the floor elevations were well within the concrete and curtainwall installation tolerances.