As the UK and global economy recovers, big projects in major cities including London are coming off the backburner. These “big” projects are often becoming taller and more slender. Buildings used to be considered slender or skinny if they were five times higher than they were wide.
Now, WSP is working on a residential skyscraper in Manhattan that is taller than the Empire State Building at 400m, but only 18m wide.
You might ask why this is happening. Real estate in prime global city locations is becoming more valuable than ever before and combined with population growth and urbanisation our property clients are squeezing more and more space out of smaller footprints. This simple equation means buildings must go up, rather than out, to create space.
There is a tendency for complex buildings such as this to be expensive, however the overall viability is actually comparable to smaller buildings because you are getting the same (or more) space out of the same plots as before.
Advances in engineering design and construction technology are enabling this shift. We now have the sophisticated design tools and technological know-how to analyse the building stability, and to make sure they will be safe and comfortable for occupants. At the same time the costs of technology are also coming down, creating a virtuous circle that gives us the confidence to make what was hitherto unfathomable now possible.
In particular ‘top-down’ core construction, which WSP has pioneered, is making this a reality. Here the technology allows us to go deeper into the ground than before, while enabling building above ground at the same time. On the Shard the first 23 storeys of the concrete core and much of the surrounding tower had been built before the basement had been fully excavated. This technique was a world first and saved four months on the complex programme.
Tall buildings are also essentially an obstacle in the sky, which impacts the wind behaviour locally and on the structure itself. The trend towards tall and slim means we must study very carefully the effects of wind on the building and at pedestrian level through modelling before planning.
Ultimately, it is our challenge to make sure occupants have high quality space to use whether it’s for residential or commercial use, despite the restrictions imposed by the tall and slim design. Engineering design is being pushed further than ever before to achieve this so it’s a very exciting time to be working in structural engineering.
Jane Richards is director building structures at WSP