Many of the issues associated with the delivery of large roofs are therefore holistic challenges that impact on all aspects of their design and construction, whether applied to distinctive architectural statements or to more conventional utilitarian buildings.
A sustainable form and function?
Stadia, as one example, have often been conceived as dramatic in scale. Many modern venues rely equally on the ability to create intimacy and social interaction at a human scale through beautiful and elegant design detailing.
But in a world where the environmental impact of the built environment, particularly in terms of embodied and operational carbon, is rightly a key focus for practising engineers, is there still a place for such iconic structures? Some can perhaps appear as wilful and extravagant, but many of the best designs have evolved to be much more than just a simple canopy or an architectural skin.
For example, the theory that many of the best stadia are designed from the inside often rings true, and the integration of the bowl and roof design is essential in generating a holistic design.
The roof design itself can be a complex interaction of architectural form, shelter, insulation, pitch conditioning (sunlight and ventilation of natural turf), acoustic atmosphere and sound quality, ventilation, the positioning of lighting, speakers, gantries, audio-visual and communications technology, camera and broadcasting platforms, rigging systems, drainage and fire protection.
Similar can be said for the roofs of other major public spaces, for example airports and ground transport hubs, or even shopping malls and public squares. Although frequently perceived as “light-weight” envelopes, they often incorporate complex back-of-house functionality that requires the seamless integration of an abundance of building services with associated access and maintenance requirements that avoid impacting on the activities below.
Therefore the inter-disciplinary coordination of a well-executed roof can be as complex as the internal design of any other building, which makes the engineering of such structures a challenging and inspiring proposition.
As an example, for the design of Al Janoub Stadium for the Qatar 2022 FIFA World Cup, AECOM’s parametric modelling of the steel roof structure, which spans over 200m, was used to optimise between structural efficiency, envelope surface area, pitch condition, the performance of the bowl and pitch cooling systems, and the incorporation of state-of-the-art lighting and audio facilities. Fine-tuning of the cooling systems involved a highly innovative and research-led approach, including transient energy modelling, sun path analysis, aerodynamic optimisation of the roof and bowl shape, and validation with physical wind tunnel testing. The structural analysis was just one of a multitude of input variables in this process.
Optimisation studies of Al Janoub Stadium roof and envelope with cooling, wind scouring and sun path studies (AECOM)