The Gridshells for the San Francisco Salesforce Transit Center

The century project TRANSBAY TRANSIT CENTER in San Francisco, designed by the architects Pelli Clark Pelli, has a spacious park on the roof level, with several skylights, for the purpose to funnel daylight into the lower floors of the building. Three of those skylights are grid shells, each consisting of a filigree grid of steel members, cables, and a double-curved, glazed surface. This paper is about the design, detailing, and construction of these grid shells. These grid shells are not extreme in span or shape; they are of a mature building type, but still innovative for most designers and engineers. The design is resulting in three structurally robust buildings, consisting of components with many varied materials, from different manufacturers, with different tolerances, brought together successfully through a holistic planning process from the beginning.