In projects with geometrical complexity, the facade engineer is presented an opportunity to understand and influence the application of parametric tools towards logical geometry by rationalizing complexity. This requires a familiarity of the parametric tools often controlled by the design architect. This paper explores the injection of the facade engineer into a parametric workflow, describing their involvement from estimating through completion of the built structure. This is a project review of the structural engineering and construction process undertaken by a specialty facade contractor responsible for the installation of the Fulton Street Transit Center's Sky Reflector-Net in New York City. The construction included an interior atrium shaped by a double-curved tensioned cable net clad by a perforated metal panel system. Light penetrates the atrium through an oculus before being redirected into the depths of the Center, providing the subterranean levels with a connection to daylight. A two-way cable net of paired cables was preassembled off-site, delivered on a spool, raised in a single lift and then tensioned. Attached to the cable net are 952 unique metal panels cladding the 8524 sf surface. A parametric workflow was implemented for collaboration between estimating, design and structural engineering using a common database of geometry information. This process was initially implemented to automate the generation of each metal panel's unique geometry. The structural analysis tool Space Gass was used to perform the structural analysis, but utilized the geometry and naming conventions common to the database so that the results seamlessly integrated back into the workflow. This first analysis validated the component sizes and details for structural adequacy. Secondly, for fabrication purposes, one of the most significant contributions from the structural model was reverse engineering to determine the initial unstressed cable net geometry. This iterative analysis was used to predict (within an acceptable tolerance) each individual cable segment's elongation to determine the initial length of each cable. Additionally, the location of each cable intersection node was determined to ensure the final form would be within construction tolerances. The role of the structural engineer in the facade contractor's collaborative parametric workflow proved paramount in establishing the fabrication, assembly and installation means and methods for the project.
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