By Luke Carothers
Opened in September of 2020, SoFi Stadium is the home of two NFL franchises: the Los Angeles Rams and the Los Angeles Chargers. Although it may seem like being the home of two major sports franchises might make the place a little crowded, SoFi Stadium has enough room for the two teams and then some. Located in Inglewood, California, the stadium is the centerpiece of the 298-acre mixed-use development known as Hollywood Park, which is part of a larger redevelopment effort in the area. Including SoFi Stadium, Hollywood Park features the 6,000 seat YouTube Theater, 2,500 residential spaces, 2 million square feet of retail and office space, an open-air plaza, and 25 acres of public parks. The broad scope of function, as well as the one-of-a-kind design, engineering, and aesthetic, firmly establish SoFi Stadium as not only a marvel of engineering prowess, but also a glimpse of what the future could be.
Such a massive project necessitated the cooperation of several firms throughout the design and construction of the stadium. It was designed by HKS, an architecture firm headquartered in Dallas, Texas. HKS partnered with Walter P Moore for structural engineering and a joint Turner-AECOM Hunt venture provided general contracting services. For the project’s lead engineer, HKS tapped Henderson Engineers, a national building systems design firm with headquarters in the Kansas City suburb of Lenexa, Kan., and an office presence in Los Angeles. Henderson, which has a wealth of experience working on stadium projects, provided acoustics, audio-video, electrical, fire protection, mechanical, plumbing, security, and telecom design services for the project.
Those who watched Super Bowl LVI in February 2022 are well familiar with the iconic, soaring facade that SoFi Stadium and YouTube Theater are nestled beneath. After many commercial breaks and during a few lulls in the game, the cameras would be trained not on the field or the players, but on the outside of the stadium, lit up in the late afternoon sun or later by the lights of the playing field. It was clear that the NFL’s production team wanted to lean on the stadium’s aesthetic beauty to leave an impression on viewers, and it worked to a large extent. However, while SoFi Stadium and the entire Hollywood Park development are certainly worthy of such praise, it is also important to note how important this project is from an engineering and design perspective.
Probably SoFi Stadium’s most well known innovation is its translucent canopy that makes it the first indoor-outdoor stadium in the world. This canopy, made from a sustainable fluorine-based plastic, keeps spectators out of the elements while still allowing natural sunlight, of which the area is famous, to wash across the fans and field. The canopy’s paneling is made from ethylene tetrafluoroethylene (ETFE). This glass-alternative is highly resistant to corrosion and can withstand a wide range of temperatures. These panels are supported by a 75,000-foot cable net system, weighing 1,450 tons, that allows a portion of the roof panels to be opened and closed. This provides vertical ventilation and temperature control for the building. Ryan Starkovich, who was the project’s Lead Mechanical Engineer for Henderson, says it took the design team numerous iterations to achieve the intended result.Starkovich notes that overcoming the challenges of such a new system took collaboration between Henderson, HKS, and RWDI, a wind flow consultant who also worked on the project.
The process of determining the correct design of this groundbreaking system involved determining both the stadium’s geometry and exact orientation as well as the different levels in which wind enters the structure. Throughout the design process of the canopy system, there were many questions that needed to be answered to make it a viable design. Among these questions were the opaqueness of the panels, which way the panels opened for ventilation, and how to best utilize the stadium’s location.
Mischa Haramia, who worked as the project manager for Henderson Engineers, says that one of the key ideas throughout the many different design iterations was maximizing the use of location by utilizing the constant cool breeze coming in from the Pacific Ocean. The difficulty of this process was compounded by the fact that, when moving around the outside of the stadium, the grade changes by up to three levels. To promote air movement through the stadium, fans are strategically placed based on the levels at which the wind enters. According to Haramia, this movement of air allows heat to move through the stadium and exit the structure vertically through the movable roof panels. This system both improves the experience for fans and protects key mechanical systems in the structure.
While SoFi Stadium’s location is certainly beneficially in terms of providing a constant cool breeze, the same location stands in stark contrast when seismic considerations are taken into account. The structural engineer, Walter P Moore, had to account for the extreme seismic environment of Southern California, which led to the stadium being constructed using what is known as a “seismic moat.” This means that the stadium’s underground structure is separated from the surrounding soil by an alternate wall system, thereby eliminating pressure from adjacent soil movement. While this structural system provides critical protection from seismic activity, it also created challenges to venting exhaust air from the structure. The team wanted to maximize floor space and didn’t want to cut holes in the building’s exterior. As such, they opted to use the space between the building’s walls and the exterior wall of the seismic moat, using it as a plenum for exhaust air that is constantly pumped at two locations. There were additional challenges, according to Haramia, because, like the foundation structure itself, the canopy system moves independently during a seismic event. This required not only predicting how each individual system will react during a seismic event, but also how these independent movements would affect the other systems.
As spectators of Super Bowl LVI and others who have attended games at SoFi Stadium can attest to, it is a one-of-a-kind experience that reflects the thought and ingenuity that went into its design and construction. After hosting the Super Bowl this past February, SoFi Stadium will also host the College Football National Championship in 2023 as well as the opening and closing ceremonies of the Olympic Games in 2028. The stadium will play host to not only the biggest events in the American sporting landscape, but also the world.
Luke Carothers is the Editor for Civil + Structural Engineer Media. If you want us to cover your project or want to feature your own article, he can be reached at firstname.lastname@example.org.