Designing an addition to an iconic museum through multidisciplinary innovation and digital-first approaches

Structural engineering

Inspired by formations found in nature, the Gilder Center’s Kenneth C. Griffin Exploration Atrium was designed to welcome visitors into a continuous, cavernous space that was intended to spark curiosity and learning. The atrium features bridges, caverns, and arching walls that not only provide a stunning open new space for visitors, but also serve as the structural system of the building. These walls and undulating alcoves make up the atrium space constructed of architecturally exposed shotcrete. The traditionally cast-in-place formed concrete would be prohibitive to realize the building’s complex geometry. The design team instead chose shotcrete, a sprayable concrete typically used for tunnels and pools, as it provided the necessary flexibility, structural strength, and finish that the architectural vision required.

While not often used for civic projects, shotcrete allows for an uninterrupted interior without material seams or joints that, once cured, also function as a load-bearing structure. This shotcrete surface was engineered to resist earthquake and wind loading, as well as to support the weight of the building’s floors. It took a carefully coordinated effort between Studio Gang and Arup to create the atrium’s geometry so that it produced an efficient load path through the structure. Cross-disciplinary planning was vital to the shotcrete design, and critical lighting and mechanical systems were integrated within the space’s main bridge and other areas to protect the integrity of its surfaces. Digital tools were also critical to the design and construction team, helping ensure accuracy and the ability to meet the project schedule. We utilized 3D-modelling tools to help fabricate and install the reinforced concrete structure. To enhance inspections, we developed parametric models containing the curved canyon rebar that could be viewed on a tablet in the field.

The Gilder Center is positioned over existing Museum infrastructure that could not be disturbed during construction at the risk of impacting Museum operations. The structural team incorporated strategic positioning of the shotcrete wall bases and the use of uniquely shaped eccentric foundations in some locations to avoid clashes with these existing conditions. A steel roof truss was also designed to fully span 80ft over the remaining existing building extent, avoiding the need for new columns and foundations through an existing mechanical space densely packed with existing services below.

Acoustics  

As a space that will be used for education as well as events and functions, the acoustic design of the atrium needed to fully support a wide range of uses while also adding to the visitor’s sense of excitement and wonder at the scale of the space with a complex volume of interconnected spaces and passageways. The Arup SoundLab was used to auralize the soundscape of the atrium and its connected spaces, including simulating the ‘babble’ of event crowds. This simulation allowed the project team to assess different options for materiality and listen to different event configurations that helped inform the overall design.

Beyond the atrium, our structures and acoustics experts evaluated the effects of vibration at the new Invisible Worlds immersive experience theatre bridge. The bridge structure supports vibration-sensitive projectors and other equipment. Considerations were made for both potential high-frequency excitation exhibited by mechanical equipment on the Museum’s roof as well as low-frequency events like human footfall. Our multidisciplinary teams worked together in identifying sensitivity limitations and creating analysis models that mimicked the anticipated events on the building structure. Based on the model observations, the team was able to make design recommendations on the concrete mass build-up required on the bridge to limit undesirable vibrations.

Banner image credit: Alvaro Keding/© AMNH