The Grace Farms Foundation’s new River Building blends into its natural surroundings, minimally impacting views across a site that was once gently sloping farmland. The LEED Silver certified project is a complex of glass-walled buildings – a sanctuary, a library, a dining hall, a classroom pavilion, and a gymnasium – that are connected by a curving, sloping, winding roof.
Silman worked closely with structural engineer Mutsuro Sasaki, a frequent collaborator of SANAA’s founding principals, during the earliest conceptual design stages. The two firms developed a structural scheme that celebrated the architect’s understated approach while meeting the project’s unique challenges and taking advantage of local design and construction opportunities.
The River Building’s structural design comprises three primary elements: nearly 200 “flagpole” steel pipe columns, continuous double-curved steel beams at the perimeter of each building, and king post roof trusses that allow for column-free interiors in long-span spaces such as the building’s gymnasium and sanctuary. Glulam girders support the smaller pavilion roofs.
The steel pipe columns, each individually fixed at their base, provide an overall lateral system that does not require crossing beams to achieve stability.
A series of wide flange beams bent in a compound curve were fabricated through a digital transfer of data between Silman and the fabricator. The curved segments, each arch about 22 feet long, were spliced together in the field, typically over the pipe columns, creating a continuous curved beam that runs along the top of the curved glass facade.
A single glulam type and size was modified throughout to address the specific challenges of the building’s various spaces. This included adding steel to create trusses over long spans and additional outrigger framing at the longer overhangs. Since the infill framing consisted primarily of standard sawn lumber (or laminated wood beams for the longer spans), local carpenters were able to build much of the roof structure.
Each truss is a combination of a glulam arch without any splice, one or two king posts, and two tension rods for the bottom chord.
