Immersed in the Sonic Sphere

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The Sonic Sphere is envisioned as a laboratory of the senses, an interactive architecture of sound, light, and movement that charts the edges of experience and consciousness. The Sonic Sphere is an ongoing project to bring all-encompassing audio-visual experiences to as many people as possible. The project has evolved over the past three years using a strategy of rapid iteration to develop the audio-visual systems, content, and structural form. The 11th iteration was placed at The Shed in Hudson Yards, Manhattan, New York City (The Shed). For this installation, the Sonic Sphere was suspended from the ceiling of The Shed’s McCourt arena.

The installation at The Shed was characterized by a breadth of tight constraints: three-month schedule (concept to opening day); material availability; coordination between many fabricators; installation with minimal heavy equipment in just two weeks; and compliance with the applicable codes.

To meet these constraints, Resurget Engineering worked with the Sonic Sphere team to develop a structure and a delivery process that was lean, adaptive, and strategically leveraged advanced analysis.

The Sonic Sphere is comprised of three major independent structural components: the geodesic steel sphere, the amphitheater structure, and the stairs/elevator platforms along with gangways.
The first is the 65-feet diameter geodesic steel sphere suspended from The Shed roof framing. The sphere supports a surrounding array of synchronized LED lights and light cloths at each intersecting node in addition to 124 speakers and 12 subwoofers that create an occupiable multisensory audio and lighting experience. The faceted sphere was constructed out of steel pipes that were bolted together at each node.

The amphitheater structure is the second independent component. The amphitheater platform was framed with trusses built from HSS members, radially attached to a cylindrical core truss. The radial trusses supported secondary wide flange members concentric to the core with custom preconstructed trapezoidal floor plates that span between wide flange beams. To achieve a structure with light and sound permeability, the floor plates were constructed with mitered channels and perforated steel grating as the finish surface for occupants to walk on. The trusses also supported custom prebuilt stairs along with seating platforms and aisles with capacity for an audience of up to 250. The amphitheater was independently suspended from hang points located at the outer ends of each radial truss that connected to cables hung from The Shed roof framing.

To get participants in and out of the shows, two independent stairs and platforms were erected from standard scaffolding framing on either side of the sphere and provided support to gangways that bridged across to the amphitheater structure. ADA access was provided by a temporary elevator.

The unique geometric and performance demands of the installation required a return to the fundamental principles of material science and dynamics to design a safe yet functional structure, while considering all project-specific constraints. To develop the design for a one-of-a-kind structure like the Sonic Sphere, with all its constraints, it was imperative to first establish the design process.

From the first meeting, Resurget Engineering worked with the Sonic Sphere team to define the limit states and loading criteria for the design to meet the intent of the applicable codes, while not overly constraining the design. Depending on the complexity of the elements considered, the type of analysis and design approach varied to efficiently engineer each component and allow for iteration.

In addition to engineering, the two main design constraints were limited material availability and the necessity for rapid assembly of the structure in an enclosed space. The coordination with suppliers was essential to utilize member sizes that were in stock and ready to be shipped to site with minimal fabrication modifications. The other constraint was to ensure members were spliced for transport, and that they could be assembled and disassembled on site utilizing light lifting equipment options and with bolted connections.

Lastly, a full 3D model of all components, geometry, and fit up, was created in Rhinoceros 3D (Rhino) and maintained by the Sonic Sphere team. This model proved to be required as a single source of truth to establish both fabrication and erection documentation.

To design the sphere struts, Oasys GSA (GSA) was utilized to conduct stress analysis and determine the load transfer between elements. GSA also allowed for non-rectilinear wind loads to be applied normal to the surface of the structure.

The sphere material supplier, Pacific Domes, had an abundance of 2-inch diameter nominal steel pipe of varying gauges in stock, which was incorporated into the design to maintain the critical schedule. The typical pipe thickness of 15 gauge was determined based on the peak tensile and compressive forces resulting from the 12 suspension points vertically supporting the sphere. These hang points induced peak tensile forces into the members radially connected to the suspension node, and peak compressive forces into the hexagon of members surrounding the node. The regular repeating geometry of the sphere was disrupted by the gangway openings, resulting in force concentrations that required the pipe thickness be increased to 12-gauge steel.

Each node of the sphere was wrapped in a tensioned fabric cover that was beneficial for the lighting experience of the show. These fabric covers significantly increased the surface area of the sphere, resulting in a much greater lateral incidental wind force being applied to the system. The lateral forces were resisted at eight nodes on the sphere, with two inclined cables at each node. This configuration insured that during any movement, at least four cables and nodes would be in tension at any given time, preventing the entire lateral load being transferred into a single node.

The sphere required coordination throughout design to accommodate limitations of the existing Shed structure regarding the allowable weights and locations of hang points. Collaboration with The Shed’s design team was essential to locate appropriate rigging locations and capacities to support the amphitheater and sphere. The gravity support cables for both the amphitheater and sphere required rigging attachments to the panel points of the existing roof framing. Based on this coordination, at each hang point, three gravity cables from the sphere were connected to a single turnbuckle per location that tied back to the roof framing. The lateral cables for the sphere tied into corner columns of The Shed.

All elements of the amphitheater platform were designed utilizing a combination of GSA, RISA-3D, and custom spreadsheets. To account for the rapid construction timeline, coordination with steel supplier County Fabricators and the detailer Rosewich Engineering was essential to determine what member sizes were readily available in stock and could be fabricated in a few weeks. This inversion of the typical workflow, where we started with sizes and had to design the spacing or length around them, led to a unique iterative design process. The transportation of these elements also resulted in dimensional restrictions where each truss had to be less than 8 feet deep and 24 feet long to fit on a standard flatbed.

Due to the timeline constraints, the platform steel framing had to be finalized and released for fabrication, prior to design and programming completion of the aisles, stairs, and seats for the amphitheater. As the project developed, it became evident that the demand at the cantilevering tips of the radial trusses exceeded the capacity of the top chord truss, due to heavier than originally anticipated super-imposed dead loads.

Rather than field-modifying the radial trusses, the engineering team developed an alternate design where the sphere and amphitheater platform were suspended as separate structures. With this new supporting approach, the differential movements of the systems had to be accounted for to prevent collisions. A finite element analysis was performed to investigate and mitigate the differential deflections based on the rigging cable layouts.

To facilitate the rapid design and construction of this unique structure, it was essential to employ innovative engineering strategies and work in synergy with fabricators, erectors, and architects to design a structure that could be both assembled and disassembled by hand in a matter of days. To achieve this end, Rhino was utilized to model every component of the structure and ensure sufficient clearance was provided for bolting connections on site. This specialty modeling was done primarily by the architectural team after specific member sizes and connection detailing was provided to them by the consultants and fabricators.

The accuracy of this Rhino modeling also aided the steel suppliers with fabrication as each element was modeled precisely and could be isolated to simplify shop drawings. Having a master model where all disciplines lived also provided instant feedback to the architectural team regarding clashes and expedited the design cycle when adjustments had to be made. This precise level of coordination was paramount to maintaining the three-month design and fabrication schedule, and assuring the on-site assembly and installation could proceed without costly infield modifications.

The Sonic Sphere at The Shed represents a cutting-edge collaboration between engineering, architecture, and art, creating an immersive experience for the audience. Through careful planning and innovative design, the project overcame challenges related to time, materials, fabrication, and space. This installation showcases the potential of rapid iteration and adaptive design, redefining the limits of structural and experiential art.

As the Sonic Sphere continues to evolve, it sets a new standard for projects that blend technology and creativity, transforming our interaction with space and sound. ■

About the Authors

Alec Thompson joined Resurget in 2022 and since then has gained project experience in multiple construction sectors across the United States. His working experiences includes a wide variety of materials as well as a specialty on structures with complex geometries.

Owjan Hashtroodi, an Associate at Resurget Engineering, brings over a decade of experience leading projects across various market sectors. His expertise covers a wide range of structures, including high-rise buildings, specialty structures, commercial and educational facilities, as well as vehicular and pedestrian bridges.

Nicholas Christie is Chief Engineering Officer at Sonic Sphere, responsible for the design and delivery of the spheres. He has 16 years experience in structural-mechanical engineering, specializing in structural dynamics, kinetic structures and large-scale art installations.

Jason Krolicki is a founding Principal at Resurget Engineering with more than 20 years of experience leading multiple award-winning projects across the world. His broad range of experience and passion for design, inspires a focus on performance and innovation.