One of the criteria for judging this year’s structural awards is “process” – what is a good structural design process? My short answer is start, plan, explore, define and test - all while searching for the best available outcome and bearing everything in mind!
My younger self would be horrified by the idea of me writing about process, as I believed entirely in free thinking, creativity, and inspiration. But I now realise that all of these can be enhanced by applying a degree of rigour, or even process.
I have become an admirer of the diamond that forms part of the “double diamond” design thinking advocated by the UK Design Council – the notion of divergent, exploratory thinking followed by convergent thinking, resolving to a solution.
In terms of application, I favour the idea that having started the design process, we then create a deliberate hiatus, step back from our design and try and gain a better perspective on what we are actually trying to do:
What does our client really want?
What outcomes are we trying to achieve? – the UN Sustainable Development Goals can be a useful reference.
Are there alternative solutions available, such as re-use or adaptation?
What is the status quo for this type of project – the best solution to date?
How could we improve on that?
What will “good” look like? – ideally with quantification, especially carbon.
How should we go about delivering this? – research, team, experts, technology, data.
Having answered these questions, we can start designing in earnest and this is where the diamond comes into action, especially in exploring the possible solution space.
I am addicted to models/simulations and advocate using the latest tools and technology to help us think. We build countless 3D structural models that help us better understand the problem, the key drivers/attributes, and begin to explore possible solutions, looking at them from various different perspectives. We will make simple models and complicated models, none will yet be the definitive model which comes later, but they will all help our thinking and understanding of the issues from a structural perspective, while also considering the project outcomes as a whole.
I also believe in the power of the subconscious, or more accurately the benefits of a relaxed brain. Putting in longer hours doesn’t appear to improve the creative process, whereas talking to others and taking time out to relax, do. After a few hours of exploration, time spent doing other things - ideally relaxing and including a good night’s sleep, seem to help both reflecting on what was learned yesterday and forming a new strategy for the day ahead – what to explore next. Peter Rice used to refer to this exploration process as acting like a hound with your nose to the scent, unsure where it will take you next.
Once our divergent exploration finishes, either due to programme constraints, or because we are happy with where we have arrived, our activity turns more towards convergent consolidation – testing our idea under perhaps arbitrary, caricature load-sets initially, to try and find any weaknesses or lack of robustness – searching for potential instability or lack of ductility, and checking service criteria such as deflection, acceleration or footfall – as a matter of principle, we should not add material (carbon) to satisfy service criteria but instead change the structure. All these aspects should be investigated before confirming our structural concept.
While exploring possible solutions there are many basic concepts that can guide us towards developing a more efficient structure: direct load paths are more efficient than bending; columns are useful; larger lever arms are more effective; basements are expensive. For unusual structures, geometry can be our friend, creating naturally efficient load paths, and double curvature tends to promote stability.
Always remembering that we are part of a team, that the structure is rarely the entire project and that we should help in making the project successful from all perspectives as an integrated design. Materiality creates an emotional response in users and can be an effective lever in reducing carbon.
Buildability should be considered from the outset – we should maximise off-site prefabrication with on-site assembly. And utilise the most efficient sizes for transport and weights for lifting, maximising safety during construction. What is the best strategy for connections?
We should have a rough solution for everything that is important. Then all we need to do is deliver our perfect design through thorough coordination, calculations, and BIM creation. Ideally the delivery process is automated using tried and tested processes, so that minor changes can be readily incorporated, and the risk of error reduced.
Deputy Chair, Arup
Tristram Carfrae is a leading structural designer. He has been responsible for the structure of a dazzling array of
award winning buildings over his 41 years with the firm, both in Australia and the UK. His particular skills relate to
the integration of engineering and architecture to provide the best holistic solution. Tristram has been fortunate to
work with many of the world’s leading architects on projects where the structure forms a major aesthetic component. Tristram is Arup’s Deputy Chair. He is one of 53 Arup Fellows (out of a global staff of 15,000). This accolade
honours those who have significantly contributed to the firm’s reputation for excellence in innovation and design and
designates him as a leader with the role of ensuring this continues. In 2014 he was awarded the prestigious Gold Medal award by the Institution of Structural Engineers.