Just prior to the start of the 2021-2022 school year, the academic expansion of Greenwich Country Day School’s Upper School was completed!
GMS provided structural engineering services for this project in Greenwich, CT, designed by Centerbrook Architects and Planners. The expansion consists of a new academic building and a new kitchen/servery building, which extend from an existing 1960’s era building. The project also includes a new exterior stair tower, which provides access to the athletic field below, and various site retaining walls to accommodate significant grade changes.
Construction spanned across the school’s campus. To the south, the new academic building consists of two sections, one of which is primarily classrooms while the other contains specialty functions such as music rehearsal spaces, fitness rooms, and mechanical systems. Due to the sloping site conditions, the lowest floor level of the southernmost portion is two stories below the lowest floor level of the classroom wing. The foundation system consists of rock-bearing shallow foundations at the lower site elevations and soil-bearing shallow foundations at the higher site elevations. The lateral load resisting system consists of structural steel braced frames and moment frames. Open web steel joists are utilized for the floor and roof framing at some regions and are closely coordinated with the MEP elements to minimize the floor sandwich. At one region, the open web steel joists span 42 feet between the column lines, while another region features truss girders that span 52 feet to support the perpendicular open web floor joists.
Throughout the academic building, there are structural supports for highly visible architectural features such as bay windows, cornices, sunshades, and a rooftop screen wall to conceal the mechanical units. Furthermore, there is a continuous canopy immediately adjacent to the west face of the building. The southern portion of the canopy has a curved layout in the plan, which follows the profile of the associated curved retaining wall.
One showcase element of this project is a spiral stair without traditional side stringers, referred to as the “physics stair.” The structure of the stair consists of 19 identical, stacked, stair tread assemblies where each assembly is rotated from the one below and connected with through bolts at each end. The overall stair acts as a shell-type structure. Each tread assembly consists of two long channels and two short HSS sections and a glass walking surface. The stair was fabricated and assembled off-site and transported to the site as a single unit.
Across the driveway from the west face of the academic building, there is a tall retaining wall and exterior stair tower to access the athletic field (teams have direct access to the new building via a new precast concrete tunnel at the field level.) The stair tower consists of reinforced concrete walls and piers for most of its height, bearing on a mat foundation. The concrete walls and piers support steel-framed landings and stairs. The upper section of the stair tower consists of wood-framed walls, which support an asymmetrical wood-framed pitched roof. The base of the roof includes a curved overhang, which is achieved via cantilevered PSL members. The reinforced concrete retaining wall varies in height and is approximately 22 feet tall at its highest, where it meets the stair tower.
The L-shaped kitchen/servery building abuts the northern and eastern face of the existing 1960’s building. Similar to the academic building, the foundation system consists of both rock-bearing and soil-bearing shallow foundations. At some locations, reinforced concrete grade beams are provided to support columns and span across existing active below-grade conduit banks. The lateral load resisting system consists of steel-braced frames. Access between the new building and the existing building is provided via a new steel-framed opening in the existing building’s load-bearing masonry wall.
View construction photos below:
View the completed work below:
Feature rendering courtesy of Centerbrook Architects and Planners. Construction and completion images by GMS.