Intuit Dome Is Nothing But Net

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The new Intuit Dome in Inglewood, California, is more than a basketball arena to the NBA’s Los Angeles Clippers, it is the team’s home away from home. The visually striking 1.1 million-square-foot arena used exclusively for basketball and concerts opened in August 2024 and is the new benchmark for global arena design and engineering.

Intuit Dome’s oblong shape is due to the Clippers’ desire to have an all-encompassing facility—the arena’s seating bowl and basketball court, administrative offices, practice and training facilities as well as the critical infrastructure to ensure the arena is carbon-neutral are all located within the structure’s footprint.

The LEED Platinum structure is completely powered by 2 MW of photovoltaic solar panels on the roof that provide 11 MW of power to batteries and related equipment housed in a central utility plant inside the structure. There is enough on-site energy storage to power a basketball game or concert while generating no new greenhouse gas emissions.

Because Intuit Dome is designed to exclusively host basketball games and concerts, it provides an intimate seating bowl for more than 18,000 fans and positions them up to 45 feet closer to the action on the court or the stage compared to traditional multi-use—i.e., hockey included—arena design.

Intuit Dome has eight distinct levels: two below grade, five levels above grade, and the main concourse at grade. The arena event level is founded at 32 feet below natural grade, and the top of the shell structure is 121 feet above natural grade.

In total, Intuit Dome is approximately 1,250,000 gross square feet and includes 965,000 square feet of elevated floor structure as well as 277,000 square feet of roof shell surface area, much larger than the typical arenas previously constructed.

Three primary structural construction typologies were instituted for the Intuit Dome—concrete substructure, steel superstructure, and the steel shell.

The concrete substructure contains the cast-in-place structure and shallow and mat foundations at or below grade. This includes the arena’s foundations, perimeter retaining walls, the slab on grade Event Level, and Club and Plaza Level elevated slabs. The east side of the Plaza Level includes concrete slab over steel deck supported by steel trusses in the loading dock area. The lower bowl also utilizes precast concrete seating units supported by steel framing.

The steel superstructure contains the structural steel elevated floor framing above the Plaza Level, which is supported by the concrete substructure below. The Suite, Mezzanine, Mechanical, and Terrace Levels are supported by composite concrete over steel decks slabs with steel beams and columns.

Additionally, steel rakers support precast concrete seating while the concession areas and electrical control rooms have bare steel deck roofs and are supported on top of the Terrace Level. The concession areas are steel frame structures comprised of wide flange beams, HSS columns, and cold formed steel shear walls as the seismic force resisting system.

Finally, the shell structure contains both the typical bare steel deck roof over the top of the arena and a polytetrafluoroethylene and ethylene tetrafluoroethylene (PTFE/ETFE) shell enveloping the rest of the roof and wraps around the structure on all sides. The shell structure utilizes circular hollow structural steel members in a diagrid shell—formed from a series of diamond-shaped panels that reflect the geometry of a basketball net—to support the building enclosure made up of PTFE or ETFE membranes. The shell structure is vertically supported by traditional columns and “tree columns” with horizontal outriggers at the Suite and Terrace Levels. A 12-in. vertical gap was provided between the Plaza Level and the bottom of the shell and is not base supported at any location. It is supported laterally at the gutter—the interface between the arena’s traditional roof and diagrid shell—as well as at the Terrace Level (radial only) and Suite Level (radial only) utilizing toggle braces.

The seating bowl is broken into five different areas—upper bowl, mid bowl, lower bowl, the dugout suite area, and the Wall.

On the east side of the arena and comprised of over 50 rows of uninterrupted seating for over 4,500 fans is the Wall. This seating bowl builds on what other athletic teams, such as Providence Park, home of the Portland Timbers, have done: putting the loudest and most passionate fans into a designated area. The resulting sound from this area is designed to funnel down to the court.

Due to vibration, and aesthetic considerations, the west side of the seating bowl required a sophisticated and unique structural design due to the massive indoor event space located under the seating area at the Terrace Level.

The west upper concourse is a propped cantilever with the seating bowl serving to counterbalance the cantilevered floor plate. This results in vibrations from the west seating bowl translating to the upper concourse floor. Careful finite element analysis (FEM) of this seating and floor area with many iterations and studies for the west side of the seating bowl was required to ensure patron comfort.

Lightweight concrete precast seating units are used throughout the seating bowl. The west side of the seating bowl is supported by steel rakers. The lateral loads are collected and delivered to the floor diaphragms with under-bowl bracing or buckling-restrained braces at the bottom section of the lower bowl. The rakers are not connected to different floor levels to prevent them from acting like building braces. The lower bowl is connected to the Plaza Level, Club Level, and Event Level to eliminate seismic joints, as discussed later in the article, at the premium suites. Connections to the club level were designed for seismic inelastic drift compatibility forces. The high stiffness of the concrete shear wall system allowed for the design forces to be reasonable.

Both floors at the Plaza Level and Club Level are in the lower bowl, consisting of concrete flat slabs supported by concrete columns. The floors were designed as two-way slabs and analyzed under gravity loads. Flexural reinforcing was placed as top and bottom base layers of reinforcing bars in both directions with additional reinforcing where flexural demands exceed the capacity of base layers. Punching shear resistance at slab-to-column connection was provided using headed stud-rails.

Concrete beams were added where necessary to provide additional stiffness to the slab at long span conditions or around large openings such as elevator pits. Forty-two-inch deep concrete beams were also used to transfer loads at discontinuous columns from the Club Level and above to the columns below.

Furthermore, the structural design of the seating bowl took a different approach to luxury suites than other arenas to keep fans close to the action. Over 40 suite spaces in a horseshoe formation are located toward the back of the middle section of the bowl—allowing fans to sit in a regular bowl seat that is exclusive to the suite. Finally, 14 court-level suites, including four dugout suites with privacy glass, line the player tunnel. The 10 suites opposite the player benches also include access to seats in the lower bowl.

Intuit Dome has a substantial basement that measures 1,300 feet and includes a 300-foot-long loading dock ramp. Coordination of the transfer trusses over the loading dock was critical because they support a column-free space for the trucks in the loading dock as well as the entire area on the east side of the arena, which is where the modular central utility plant battery storage is located. The central utility plant includes over 180,000 pounds of batteries and related equipment, drive aisles, and storage yards on an elevated structure. Intuit Dome was engineered to be self-sustaining and allow the incorporation of ever-changing technology and sustainable practices even throughout construction.

The upper concourse on the west side of Intuit Dome is a massive indoor-outdoor space at the Terrace Level. The structural design of the 35-foot cantilevered terrace used steel kickers for support. The very top of the west side of the arena on the Terrace Level features four basketball hoops with netting on the side, an auto-return system to get the ball back to the shooter, and an electronic scoring system for the team’s Shoot 360 interactive experience where fans can play. Several shade trellises were added for the outdoor concession areas.

On the east side of Intuit Dome, the glazing was designed for blast loads and engineered to ensure the safety of the patrons and the structure. The back up steel for the glazing consists of W24x columns and a cable system behind the glass to prevent any glass from entering too far into the interior space.

Also on the east side of the arena is a promotional basketball court that has a 60 feet ceiling space from the main deck all the way up to the upper concourse. A series of 95 feet long trusses support the concourse above this area. Structurally, the challenge centered upon the very large façade attached to the HSS cladding girts between the steel columns. The four-story steel columns are supported by concrete beams under the southern section and steel beams and trusses supporting the northern portion, resulting in differential deflections and complications to the glazing design. The steel columns and framing at the concourse are designed for blast loads. Additionally, the trusses in this area were designed to minimize the vibration felt on the terrace level above.

Structural design for the arena’s closure wall above the concession structure also took on special considerations due to the proximity to the roof shell and the differential movements. The walls were cantilevered from the top of concessions to allow for differential movement of the shell. The shape of each concession area is engineered with a curvature along the backside wall so it would avoid contact with the exterior shell but maximize interior space. This curved design of the concession areas is unique compared to traditional arenas with concession areas typically built as masonry boxes. Concession structures utilized sure board, light gauge steel panel shear walls for the lateral system and bare metal deck supported by steel framing for the roof gravity system.

Intuit Dome’s PTFE/ETFE roof shell rides along with the structure; however, it is not the primary structural seismic system. The 2,800-ton diagrid shell frame roof is supported by seven trusses over the main arena weighing approximately 120 tons apiece and is comparable to a “hoopskirt” where it is rigid in its own way but then tied back to each successive floor with a toggle brace.
Because Intuit Dome is located approximately a mile from the Newport-Inglewood fault, the toggle braces can rotate in two directions in case of a seismic event. The toggle braces allow the shell to be laterally supported by primary structural floors at Levels 4 and 7 so the shell frame roof does not cantilever over 100 feet. However, because the toggle braces can rotate using universal pins, the shell can move freely during a seismic event and not experience high loads due to drift compatibility that would otherwise rip apart the shell. In this way, the roof shell acts as a façade element and not a primary structural element.

Additionally, the PTFE/ETFE diagrid roof shell that makes up the exterior of the arena covers the entire structure. The decision to use both PTFE and ETFE ensured the material could stretch over multiple panels because the diagrid roof shell has several different configurations. The dual roof material is watertight in the critical sections of the structure and a woven mesh in other areas to allow ample natural light and airflow, while also providing a horizontal and vertical decorative aspect.

One unique aspect of the roof is how it is used—or not used—over Intuit Dome’s indoor-outdoor lobby. The partially covered lobby, which includes the main entry and ticketing areas, measures 25,000-square feet and reaches 115 feet upward to the roof shell. The indoor-outdoor lobby is unique in that most venues have lobbies that are completely enclosed or completely outside. Different sections and portions of the roof are open to allow light and air in to provide the aesthetic design qualities required by the Clippers. The roof is waterproof over the court, seating bowl, upper concourse, and one bay beyond the concession buildings at Level 7. Beyond the enclosure line, the shell acts as a shading and architectural element.

The lobby’s indoor/outdoor nature allows the structure to use the Southern California climate for natural heating and cooling. There is no need to heat or cool a massive volume unnecessarily, resulting in a much more sustainable approach to traditional arena heating and cooling.

The team’s 71,000-square-foot, four-floor administrative building houses the team offices and is located above the practice facility and training center. A portion of the administrative building is above-grade and visible to fans inside and outside of the arena, but the 86,000-square-foot, two-level practice facility and training center that includes two basketball courts, training, medical, and player spaces is primarily located below grade. The areas below-grade required a series of transfer trusses to ensure column-free spaces for the two practice courts and outlying areas. These steel trusses, which span 145 feet, play a critical role because they support the four floors of the administrative building above.

Above-grade, the exterior space around Intuit Dome includes a sunken garden on the west side, which is a private outdoor space for the team that includes a swimming pool, infrared sauna, outdoor track, lounge, and eating area. The sunken garden allows natural light into the training facility and practice courts while also providing privacy for the team.

The shell ties together all the different structures—from the arena to the admin buildings—under the entire roof. As a result, the lateral system of the admin building was tuned to prevent significant force transfer via the overhead shell.

Furthermore, the administrative building has vibration sensitive criteria that is exacerbated by supporting four floors on top of it in a staggered manner. In addition to keeping the floors level and acceptable for vibration, the trusses could not be increased in depth without impacting the practice court below. The discontinuous nature of this area forced the buckling-restrained brace lateral system to the extreme ends of the floor where columns connected all the way to the plaza level. This put significant seismic forces—up to 1,200 kips—on these floors and the buckling-restrained braces but allowed the transfer trusses to be designed without amplified seismic forces that would be required if braces landed on the trusses.

Contrasting the structural system layout used for the braces in the administrative building, within the arena the braces are spaced much closer together—70 to 80 feet apart compared to 140 feet apart within the administrative building.

Unique to Intuit Dome is its double-sided halo 4K scoreboard that features more than 233 million LEDs—the largest ever double-sided halo display in an arena setting—and similar in design to the Infinity Screen at nearby SoFi Stadium.

Most, if not all arenas, have a center hung scoreboard. Walter P Moore provided design and detailing to accommodate the unique shape and design that is well outside the norm for traditional center-hung scoreboards. The halo scoreboard’s scale is significant, with a continuous perimeter that encircles an area larger than the basketball court and a height that allows the upper-level seating a generous view of the 30-foot-tall continuous screen.

Due to the complexity of size, shape, and weight, the halo scoreboard consists of vertical and horizontal trusses curved in plan to multiple segmented radii. It is a continuous structure with discontinuity only at two ends where there is a retractable segment for use during specialty shows and events. The halo scoreboard is hung from above where it crosses primary roof truss panel points. Because of this, the entirety of the halo was incorporated in the analysis of the roof structure to account for load redistribution and stiffening effects. Walter P Moore was also contracted to work in direct coordination with the erector and fabricator to provide construction and erection engineering services to facilitate speed and erection sequencing of the halo structure.

The halo scoreboard optimizes sightlines from all seats and places a priority on the viewing experience of fans seated in the upper bowls of the arena.

Comparable to the complexity of the structural design for the scoreboard is the internal rigging system used for concerts. The upper echelon rigging capacity is designed to handle the increasingly large loads for modern concert tours. Each individual rigging beam can support 5,000 pounds vertically or in a bridled configuration. From there, several different configurations were evaluated where a series of 5,000-pound loads could be placed throughout the arena, allowing for a maximum of 75,000 pounds on an individual truss but not more than 525,000 pounds using the seven total trusses inside the arena. The significant rigging capacity allows the arena to be a premier concert venue in addition to a tremendous basketball viewing experience.

The seismic base for Intuit Dome is 32 feet below the arena’s natural grade. Seismic resistance is provided by a continuous perimeter concrete retaining wall and interior concrete shear walls. Above grade, the steel superstructure is utilized for gravity and seismic support with a buckling-restrained brace lateral system that provides lateral resistance and is transferred to the concrete shear walls below.

Comprising the roof and exterior envelope of the building is the iconic shell structure. It is part of the steel superstructure; however, due to its unique shape and configuration, all shell elements—generally above terrace—were treated as a diaphragm with overstrength loading design forces.

The steel superstructure utilizes a buckling restrained brace lateral system at the occupied floors above grade. The system stacks vertically and uses a single diagonal approach. The arena and administrative offices do not connect to the floor diaphragms from the architectural layout at Levels 5-7 and through a seismic joint at Level 4. However, the arena shell structure is supported above Level 7.

Buckling-restrained brace frames were analyzed with continuous columns and fixed or pinned connections at beam ends corresponding to the details used. Buckling-restrained brace frame column bases were modeled as pinned to maximize the design forces in the braces and detailed accordingly to minimize rotational strength and stiffness at the base.

For the concrete substructure, a special frame concrete shear wall utilizing the basement retaining walls and interior shear walls also support the buckling-restrained brace system above. Special shear wall detailing, and provisions utilize ACI 318-14 (Building Code Requirement for Structural Concrete) with the exception of Grade 80 reinforcement. The diaphragm was cast-in-place reinforced concrete slabs with the east side of the Plaza Level utilizing concrete over steel deck diaphragm over the loading dock. A static linear approach with equivalent lateral force procedure was used for the concrete superstructure design.

The construction of Intuit Dome is a landmark for the Clippers franchise, which has never owned its own arena. The eyes of the world will be on Intuit Dome this fall as a series of concerts will be held prior to the Clippers opening of the 2024-25 NBA season. In addition, the arena is slated to host the 75th NBA All-Star Game in 2026 as well as events for the 2028 Olympic Games in Los Angeles.

Intuit Dome’s concept of a fan-first arena that includes ample public spaces and recreational facilities is a design engineering marvel that may jump-start an exciting new era of arena construction around the globe. ■

About the Authors

Ryan Anderson, SE, DBIA, is a Principal and Managing Director in Walter P Moore’s San Diego office (randerson@walterpmoore.com). Sam Bass, PE, is a Project Manager in Walter P Moore’s Los Angeles office (sbass@walterpmoore.com).