From Taylor Swift to Manchester United: how stadium design is changing

The use of sport venues for more than just sports is increasingly popular – and a trend that looks here to stay, certainly with Manchester United’s proposed new stadium. But how is the construction industry responding to this change and improving design and engineering of multipurpose venues?

Part of that response will come from an update of the Institute of Structural Engineers’ (IStructE) Dynamic performance requirements for permanent grandstands subject to crowd action guidance. The first iteration was published 17 years ago and work is underway to revise this guidance to provide designers with more information, improve the ease of application and, ultimately, create more efficient stadia designs that meet a variety of needs.

Understanding the impact

Years of practice in design, construction and operation of buildings and continuous research have helped designers better understand the dynamic behaviour of building structures. This has led to development of new tools and methods of analysis to assess structural vibrations which enables engineers to achieve lighter and more efficient designs.

Structural vibrations are often considered in a context of work efficiency, occupants’ personal comfort and performance of sensitive equipment. However, in some cases vibrations may become a structural safety hazard, which requires strength checks to be carried out.

The acceptable levels of dynamic performance depend on “design event scenarios” selected for the venue. These represent different types of crowd behaviour and different crowd make-ups for active and seated audience.

Newly built high-spec venues in the UK are typically designed for Scenario 3 and 4, which cover high energy concerts – like those of Taylor Swift and Oasis – and high-profile sporting events, such as Premier League football fixtures. Scenario 1 typically covers sporting venues where the maximum capacity is not expected to be reached while Scenario 2 is for classical concerts or sporting events with an audience that typically remains seated.

Inaccurately predicting the dynamic response during design, or use of a venue for a different scenario than it was designed for, may lead to complaints of unsettled spectators, damage to decorative finishes and poor performance of TV equipment supported off the grandstand framing.

In extreme cases, it can result in panic and uncontrolled evacuation of spectators from spaces experiencing alarming levels of vibrations. Such problems might result in occupancy limitations, crowd management using stewarding, and structural enhancements, leading to an impact on the cost and operation of venues.

Vibration assessment

The 2008 guidance from IStructE offers designers two assessment methods – compliance with natural frequency requirements, known as Route 1, or designing for managed events where the performance is measured in accelerations and displacements, known as Route 2.

Route 1 requires the structure to be stiff enough to exceed prescribed frequency limits but potentially results in inefficient design.

The Route 2 method requires complex “time-history” analysis using finite element software with “body” elements modelled to simulate the crowd moving on the structure, whether that’s motion in time with music or the less synchronised football crowds. The Route 2 method usually leads to more efficient and cost-effective designs than Route 1 and has been successfully used on UK projects for more than a decade, generally with no problems associated with crowd comfort reported.

Nonetheless, it may be difficult to achieve a satisfactory level of structural response for the entire grandstand without significant structural modifications, which may lead to uneconomical designs. In these cases, crowd management and planning, supported with relevant risk assessments, may be implemented provided that the structural safety is not compromised.

The recommended comfort criterion for horizontal excitations is achieved by raising the structure’s natural frequency to more than 1.5Hz. The recommended limit can usually be satisfied for relatively shallow grandstands.

However, in the case of tall, large capacity arenas, achieving this is usually not feasible or associated with inefficient structural design. A lower frequency limit may be considered, which has been a case for several large stadia in the UK. The Route 2 method can also be used provided that suitable crowd motion properties can be reliably established. However, as fully synchronised crowd action reduces for larger groups of people, a risk evaluation may also be included in the assessment.

Acceptable levels of dynamic performance recommended for vertical excitations in multipurpose venues are significantly higher than is normally advised for general occupancy floors.

Therefore, control of motion within floors that are structurally connected to grandstand elements, such as via raker beams, may become a significant challenge and can easily govern the design of the structure. In cases where structural separation or changes to functional planning are not feasible, risk assessment and advice on suitable crowd control measures may be used.

Stadia of the future

Work on IStructE’s guidance update in collaboration with industry leading experts started in 2023. The work aims to aid better design of new stadia such as Manchester United’s planned venue, whether they are for single use or multipurpose.

Further research is needed regarding horizontal and vertical excitation due to coordinated rhythmic activity, including dynamic action of groups of fans that have rehearsed bobbing or jumping.

Additionally, provisions for safe standing on terraces need to be developed.

In tandem with the new guidance, alternative solutions are also being developed by industry to provide supplementary damping to structures as a more cost-effective solution than adding mass and stiffness. These innovations could also hold the key to more economically practical solutions.

While both the design guidance and new technology that goes into future sports venues is yet to be seen, the rapid sale of Oasis tickets last autumn shows that the demand for multipurpose facilities is here to stay.

Wojciech Markowski is a technical director at Mott MacDonald.