Designing for Disassembly at Stadium 974

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Large short-term international events like the soccer World Cup or the Olympic Games require suitable large stadia to host them. Where the existing infrastructure is insufficient, host countries or cities construct new stadia specifically for the event. Following the event these new stadia are often underutilized due to a mismatch between a stadium’s characteristics and long-term demand, such as new stadiums having: a larger capacity than needed, being sited in inaccessible locations, or being surplus to the typical event use requirements of the host. An underutilized stadium—a White Elephant—can have both negative impacts on the surrounding community and be expensive to maintain. It is also a waste of economic and material resources; making it hard to justify the emission of greenhouse gases associated with its construction.

Stadia are built to be enjoyed. Yet, unlike residential or office buildings that are regularly occupied, stadia are used only sporadically. Typical metrics for comparing the environmental performance, such as kgCO₂e/m² or kgCO₂e/seat are less informative than metrics that evaluate the embodied carbon emissions per stadium use, such as kgCO₂e/seat/event. This can be illustrated by comparing two similar stadia over the first 20 years of their life: one that is regularly used by a club soccer team, and another that is built to host a short-term event. Both stadia could have associated embodied carbon emissions of 1000kgCO₂e/seat, however due to the number of events each stadium hosts there could be an order of magnitude difference in the embodied carbon emissions per stadium event: a club stadium hosting 25 matches a year would have 2kgCO₂e/seat/event, while a short-term event stadium hosting 10 events in the first month followed by two events each year would have 20kgCO₂e/seat/event.

Structural engineers are implored by the SE2050 challenge to “understand, reduce and ultimately eliminate embodied carbon in their projects by 2050.” The first and most impactful step a structural engineer can take in reducing the embodied carbon of our project work is through reviewing the brief and interrogating project needs to avoid the construction of underutilized structures. This where the application of circular economy principles such as design for disassembly (DfD) and structural element reuse can have the largest impact. This case study presents some of the key DfD decisions that were taken for Stadium 974, focusing on: simplicity, generality, modularity, transportability, reversibility, rationalization, and tracking. The goal is to demonstrate how DfD principles can be implemented on large-scale commercial projects.

Three successful strategies to avoid constructing underutilized stadia have been demonstrated by past hosts of large short-term international events. The first strategy avoids new construction altogether by using available existing facilities, such as at the Paris 2024 Olympics—constructing only one new permanent venue—or the UEFA 2024 European Championship hosted across Germany in eight existing club soccer stadia. The second strategy involves careful planning of the stadium legacy to ensure that any constructed stadia are utilized after the event, such as at the London 2012 Olympics where temporary stands were removed to reduce capacity, and long-term use deals were made with community stakeholders. However, these strategies are only suitable for economically developed hosts who have large permanent local populations that have either justified previous infrastructure investment or can benefit from long-term future infrastructure use.

A third successful strategy is to design temporary structures that can be removed following the event, such as the aquatics and handball venues at the Rio 2016 Olympics or the International Cricket Council T20 World Cup stadium in Nassau, NY. For host cities and nations with relatively small permanent local populations, removable temporary structures can avoid the burden of constructing and maintaining white elephants. However, these temporary venues are typically small capacity, built using generic modular systems that require large areas to assemble, and do not allow for dense use of the space below the stands.

To host the FIFA World Cup Qatar 2022 Qatar built eight stadia with a combined capacity of 380,000. This is a long-term oversupply of stadium capacity, sufficient to simultaneously seat 1 in 7 of the population. To reduce the number of underutilized stadia following the event, one of the venues—Stadium 974—was designed as a unique temporary facility: Designed to meet the demanding requirements of a FIFA World Cup stadium, with a 40,000 capacity multi-tiered venue and roof covering all seats, it is also the first fully demountable stadium of its kind. The inventive design allows the stadium to host 13 events then be disassembled, transported, and reassembled elsewhere.

The suitability of DfD as a strategy for reducing the environmental impact of structures is primarily weighted on three factors: how many times will the structure be reused, how far will it be transported between its uses, and the additional embodied carbon associated with building a structure specifically for disassembly. A DfD structure can have a higher upfront embodied carbon investment compared to a conventional one-installation structure, due to element rationalization and connections which facilitate easy disassembly and reassembly. A study prepared for FIFA – Greenhouse Gas Emission Analysis of a Demountable FIFA World Cup Stadium – compared a combined average of the embodied carbon of four other 40,000 capacity permanent stadia constructed for the event against Stadium 974, estimating that Stadium 974—including the structure, services, and finishes—had over 60% more initial embodied carbon emissions. For DfD to be a sustainable strategy, this initial investment in embodied carbon must be counterbalanced by reusing the structure to avoid new construction; a DfD structure must be disassembled and reused to justify the investment of the initial upfront embodied carbon. Finally, the carbon dioxide emissions released from transporting the structure must be monitored: if a DfD structure is transported too far then the avoidance of new construction emissions may be outweighed by the emissions released due to transport. The same FIFA study concluded that, if reusing Stadium 974 once, it could be transported over 4350 miles and still have a lower total embodied carbon than building a second new stadium from scratch (Fig. 1)—equivalent to the distance from New York to Peru by water.

Stadium 974 is a DfD structure first assembled on the east shore of the Doha Bay in the municipality of Ras Abu Aboud, Qatar. The stadium occupies an area of 695 feet x 656 feet on plan and at its highest point is 154 feet above ground level with no basement. The design concept is based around a highly repetitive grid of identical structural frames, supporting standardized modular components: bleachers, concourse slabs and custom shipping containers pre-equipped with services. Stadium 974 was designed to be demounted after the event and relocated, either to be reassembled as a complete stadium or repurposed into alternate configurations at different locations (Fig. 2).

Structural joints are located between the curved and straight sections of the stadium, resulting in eight different sectors on plan which are split into two tiers of stand modules and one level of roof modules. The specific legacy designs focused on five alternative configurations of the modules: a 20,000-capacity soccer stadium, a 7,500-capacity swimming pool complex, a 7,500-capacity multipurpose pavilion, and two 5,000-capacity athletics stadia.

Stadium 974 was conceived as a simple structure. The stadium structure consists of a series of steel braced frames resembling the appearance of a high-bay warehouse on a larger scale; while a high-bay warehouse is designed to support goods on standard 40 inch x 48 inch packing pallets, Stadium 974 is designed to support programs in standard 8 feet x 40 feet shipping containers. Basing the design around a standardized volumetric unit enables the structure to follow a regular grid with repetition of structural element lengths within the frame (Fig. 3).

The frame features efficient direct vertical load-paths and regularly spaced bays of stiff bracing struts. Horizontal diaphragms are created on each level through tension rod cross-bracing, avoiding the need for the floor system to act as part of the horizontal lateral system. The column elements are pinned at their base, and bending stiff from bottom to top with pinned connections between the columns and the radial and tangential girders. The frame follows an approximate 30-foot grid.

The structure of the bowl and roof is divided in eight sectors: four straight sectors and four corner sectors, each separated by expansion joints. The expansion joints feature a sliding connection between the last bay of tangential beams and purlins of the straight sectors and first radial frame of the corner sectors. If the structure is reassembled in an alternate configuration, then additional elements may be required at the expansion joint to complete an independent self-stable sector module. The external circulation cores are designed as completely independent laterally stiff structures uncoupled from the primary bowl.

The roof structure follows the bowl grid and consists of a series of radial main trusses supported on the outer perimeter columns by means of V shaped supports, cantilevering 89 feet over the short sectors and 177 feet over the long sectors. The cantilever is counterbalanced with back stays connecting the back of the roof main trusses to the foundation level. The roofing consists of uninsulated trapezoidal sheet spanning 15 feet in the radial direction over tangential purlins.

The main structure was analyzed and verified according to the Eurocodes. Along with the International Code Council this is one of the two dominant design code methodologies used globally, allowing for good cross-compatibility with other jurisdictions when the structure is relocated, and easy understanding of the analysis and verification process when the structure is reviewed by local engineers.

The lightweight slab panels, bleachers, containers, and modular staircases were all verified for compliance to strict stadium serviceability limit states for vibrations, limiting the lower vertical frequency to six Hz to allow for the maximum flexibility of future use scenarios. All concourse slabs are designed for a 105 psf live load to allow for future interchangeability. All the cross sections were designed to ensure no plastic strains occurs in the ultimate limit state to avoid permanent deformation which could restrict disassembly and reassembly.

Wind, temperature and seismic loading were incorporated based on the specific environmental conditions of the stadium in Doha. If the stadium is reassembled in its entirety in its next location, then loading conditions will need to be verified against the initial design assumptions; if the stadium sectors are reassembled in an alternate configuration, then the overall stability design will need to be reanalyzed. The MEP services have also been designed in a modular arrangement with reuse and flexibility in mind. However, depending on the new location and configuration, the services strategy may require some power, heating, and cooling adjustments.

The stadium’s name and its common moniker—Container Stadium—both highlight the modular concept behind the stadium; a total of 974 specially modified shipping containers were used to allocate all the required functional spaces of the stadium—ranging from hospitality suites to restrooms, and concession stands to mechanical plant rooms. In some cases, clusters of up to three containers were connected to achieve the required functional area. Many variations in container customization were considered, such as the complete removal of load-bearing walls of the container, or differing load requirements. In all situations the base of the container acts as the permanent structural slab, with no additional slab below.

All other walking and seating surfaces in the stadium are lightweight modular steel systems that can easily be removed, stacked, and reinstalled interchangeably throughout the structure. The focus on lightweight structures is to easily facilitate installation and demounting, to reduce the structural demand on the primary frame and foundations, and to reduce the total weight of material that must be transported to a new location. These lightweight systems contrast with typical concourse and bleacher solutions made from heavy precast concrete components. The concourse slabs are thin gauge orthotropic steel plates that weigh less than 20 psf and span 30 feet between tangential beams. The bleacher elements are single folded steel plates, bolted to the adjacent elements and raker beams resulting in a very efficient, stiff and flatpack solution.

For a DfD project to be successful, as many of the barriers to future reuse must be removed as possible. A key design focus of Stadium 974 was to plan for future transportability of the structural elements by ensuring they could be fit within a standard 40-foot shipping container. Nearly all of the structural elements were designed to be less than 40 feet long through the selection of the overall 30-foot structural grid and the arrangement of the column and raker beam splice locations. This structural grid also ensured that all insert modules—such as the bleachers and concourse slabs—were capable of fitting within the containers.

However, within the design two structural elements would typically require elements that exceed the 40-foot limit—fabricated portions of the longer cantilevering roof trusses, and the backstays tying the roof down to the ground. The backstays were subdivided into four segments that are spliced together on site, while the long roof trusses were left as a small number of special items that instead of being transported within a container would require space on a ship deck. If transportation of the trusses on the deck of a ship is not feasible, these elements could still be subdivided and spliced into individual lengths less than 40 feet.

To facilitate future disassembly all the connections between elements, and splices along elements, are designed as reversible. Splices in continuous elements such as columns, raker beams and backstays are achieved through bolted headplates that can transfer moments. All connections between elements—beams to columns, bracing to nodes—are resolved with single pin connections. Much of this reversibility is achieved by condensing the complexity of the connection into an isolated fabricated central node. The design approach using single pins simplifies the assembly and disassembly process and has the potential to reduce the size of the connection zone when compared to a more conventional multi-bolt solution.

In addition to incorporating reversibility in the structural design of the connections, it was also important to embed the process of assembly and disassembly into the design. Each connection was modelled in a 3D CAD environment including the presence of MEP and architectural finishes to simulate the restricted access to the connections and confirm the installation and de-installation sequence. The concourse slabs and containers are fixed to the tangential beams using a standard flange-clamping system.

Successful rationalization of structural cross-sections in a design is about finding a balance between minimizing the use of material by designing each element close to 100% structural utilization while also taking advantage of the fabrication and installation efficiencies of grouping elements. In addition, for a DfD structure rationalizing the element sizes allows for increased interchangeability between elements in the design. This was achieved in Stadium 974 by rationalizing both the overall cross-section dimension and cross-section thicknesses. All columns in the stadium were selected from one of eight square hollow section sizes with three outer dimensions and three plate thicknesses.

Rationalizing beam and column cross-sections still leaves an extensive range of potential column-to-beam connection configurations. A standardized connection detail was developed that could be flexibly applied to different combinations of cross-section sizes. The concept was based around a set of four channels welded to the outside dimensions of the columns, a standardized pin length, and doubler plates to make up the dimensional tolerance. Depending on the column dimension, the connecting beams either slot over the channel or within it.

A key difference between conventional one-installation structural design and DfD is in the requirement to maintain knowledge about which structural elements are which through disassembly, storage, and reassembly. Stadium 974 used an alternative to the impermanent element tagging systems—paint sticks, paper or plastic tags—that are typically obscured by paintwork. Instead, each steel beam and column in Stadium 974 has a visible QR code attached, allowing the contractor to scan and read element information. The ability to scan and digitally organize elements is helpful for initial assembly, but crucial for disassembly, storage, and tracking through the container transport process.

The presence of individual QR codes on elements also allows for the development of material passports—digital identity documents cross-referenced to each element which store additional further information, such as material grade, design capacity, and element embodied carbon.

The only elements of the structure of Stadium 974 not designed for disassembly and reuse are the foundations. Foundations are specific to a location’s geotechnical conditions, and their design can often vary from one end of a structure to the other. Additionally, foundations are typically made of concrete, making them substantially heavier than the elements in the structural steel frame. Transporting heavier construction materials releases more carbon dioxide emissions per mile travelled, thus reducing the benefits of DfD. For Stadium 974, new foundations would need to be installed at any future locations as part of the reassembly process.
For Stadium 974’s first installation in Doha, a combination of favorable site conditions (a thick layer of Simsima limestone) and a lightweight stadium without concrete bleacher or concourse slabs allowed for relatively small shallow isolated concrete pad foundation at each column location with limited excavation required.

The inclusion of these DfD features on a large-scale commercial project led to some unexpected challenges. The transportability of the system allowed for complete off-site fabrication in a workshop, which led to a comparatively fast on-site assembly sequence. However, the use of reversible single pin connections on site imposed tight construction tolerances of 1/8 inch, which required a trial assembly of large portions of the bowl frame and roof in the workshop to confirm the tolerances had been met. The only adjustability for tolerance available on site was in the bolted head plate splices in the columns, backstays and raker beams.

The use of steel for all superstructure elements means the embodied carbon emissions total of the stadium is particularly sensitive to the extraction, transport, and manufacturing of the steel. The steelwork for Stadium 974 was fabricated in Vietnam and then transported to Doha for installation. Fabricating DfD structures using steel from lower-emission steel-producing regions, such as the US, could reduce the total embodied carbon associated with the project. A second strategy to reduce the initial embodied carbon of a DfD structure would be ensuring that the fabrication facility is closer to the initial target installation site. The distance from the Port of Saigon to Doha is over 5,000 miles, while the maximum distance that the stadium should be transported for one reuse was estimated at 4,350 miles. If this initial material transport distance was reduced, the final sensible relocation distance could be increased.

It is expected that both the rationalization of the structural elements into fewer size groups and the fabrication of standardized and reversible connections may have led to an increase in material usage in Stadium 974 compared to an equivalent conventional one-installation design. sbp plans to complete a detailed analysis comparing Stadium 974 to an equivalent stadium design for one-installation. This direct structural comparison will allow us to understand the embodied carbon implications of each of the individual structural DfD decision categories, such as rationalization and reversibility.

Stadium 974 is the first completed stadium project at such a large scale to be successfully Designed for Disassembly. It can act as a prototype for other ambitious projects to apply circular economy principles and presents a series of interconnected design topics which should be considered in DfD projects. The discussion of demountable stadia also hopes to demonstrate the potential clarity in assessing the environmental performance of stadia projects based on their embodied carbon per event instead of their embodied carbon total.

About the Authors

Dan Bergsagel is the international Sustainability Lead for schlaich bergermann partner (sbp) based in their NYC office, and is a visiting scholar at Cornell AAP’s Circular Construction Lab. He chairs the Circular Economy Working Group for the ASCE Structural Engineering Institute Sustainability Committee. (d.bergsagel@sbp.de)

Knut Stockhusen is a Board Member and Managing Director at schlaich bergermann partner. He developed the innovative concept for the modular container stadium and realized it with the team for the first time as Stadium 974.

Christoph Paech is a Managing Director at schlaich bergermann partner’s Stuttgart office and leads sbp’s special structures team. Stadium 974 is one of many international sports arena, stadia, and other large-scale projects that he has successfully managed.

Fernando Sima is a Director at schlaich bergermann partner’s Berlin office. He was part of the team that planned and executed Stadium 974 and acted as sbp’s design representative in Qatar during the design and construction phases.