Digitising the wind to create tall, skinny buildings

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14 November 2019 | 7 min | Article

As tall buildings become more complex, the importance of understanding the impact of wind increases. To address this growing need, Aurecon developed an industry leading Digital Wind Method for analysing the effects of wind on tall and skinny buildings. This innovative and unique process brings unprecedented insights and accuracy to work, opening new possibilities in complex design.

According to the fashion industry, the 2010s has been exemplified by tall, skinny jeans. As the father of two daughters not quite at the fashionista stage, and with a typical dad bod, all I can say is “I wouldn’t have a clue”. But as a structural engineer I agree that the 2010s has been all about tall and skinny, in terms of the fashion for buildings, not jeans.

When it comes to ‘feeling the breeze’ on these supertall structures, engineers are faced with one of the most complex modern design challenges, and this is where digital technologies have been able to help provide some innovative solutions.

New challenges for tall buildings

Super tall buildings are growing in height exponentially. The kilometre-tall building is already being built. The mile-high building has already been conceived. The world has an insatiable appetite for tall buildings, and as engineering, technology and urbanisation progress, that appetite is increasing.

However, the development of some of these mean feats of engineering can be driven by what we call ‘vanity height’. In these cases, the tops of these buildings are often unoccupied space. This means occupant comfort criteria, such as avoiding motion sickness under wind-induced building motion, may not be a key concern at the very top of these record-breaking structures, and may not need to be assessed for such stringent criteria.

However, one super tall tower is going to change that status quo.

CASE STUDY

Dubai Creek Tower

The Dubai Creek Tower, designed by world-renowned architect and engineer Santiago Calatrava, features occupiable space located in the circular-shaped bud at the very top of the structure. Aurecon is proud to be working on this spectacular new project, as the engineer/architect-of-record, supporting the team from Calatrava on a range of design and technical features.

Everything about the Dubai Creek Tower is extraordinary. For example, Emaar Properties, the developer, has commissioned a comprehensive array of never-before-seen wind tunnel tests for the structure. Aurecon worked with the team from Santiago Calatrava on this, supporting 12 different analysis and testing methods to ensure that all possible cases are considered, to ensure the maximum quality and safety of the structure.

An essential aspect of the testing was to study and control the building’s movements and accelerations so that key comfort criteria are achieved for visitors to the circular-shaped bud at the top of the structure.

The new frontier is skinny

Traditional supertall buildings require big plots of land to sit on, but this is becoming a challenge in established cities where most of the land has already been developed. Today, 50 per cent of the global population lives in urban areas, but those cities cover only 3 per cent of the world's land. So big plots of land in urban centres are increasingly rare. Urbanisation is not just changing the landscape, it’s also changing the cityscape.

This creates unique problems, or as we call them at Aurecon, wicked problems, but as engineers we love a challenge! To cope with the lack of available land, over the past decade cities like New York, Hong Kong, Bangkok and even Melbourne have created pencil-thin building designs. To maximise the developer’s return on investment for those buildings, the focus is on making them as tall as possible – supertall.

One example of this is the Ateliers Jean Nouvel-designed Soontareeya tower that Aurecon is working on in Bangkok, for Areeya Property PCL. The developer has only a very narrow piece of land so is creating a super slim tower to fit on it.

But how slim is ’slim’? Well, to give you an idea, take a look at the proportions of your smart phone: that slimness to height ratio is what’s planned for Soontareeya, nicknamed ‘the iPhone tower’. As you can imagine, these super slim buildings are incredibly challenging to design. Structural stability, building motion and occupant comfort are important considerations, so accurate wind modelling is vital.

Digital Wind Method

To help solve the challenges faced on these unique structures, our unconventional thinkers at Aurecon developed the innovative Digital Wind Method by marrying the accuracy of traditional wind tunnel techniques and the power of modern computing to create real time digital simulations of wind events passing through the building’s structural analysis computer model.

The Digital Wind Method allows us to repeatedly run real time digital simulation of frequent and rare wind events without needing to go back into the wind tunnel, hence saving valuable time in design development. Of the many advantages our innovation brings, the most notable is the ability to repeatedly design, test and optimise the performance of the structure to minimise the building’s lateral movements and accelerations, which are key occupant comfort performance criteria. This is also the most unnoticeable feature of the Digital Wind Method.

The digital wind method applied to Aurecon's Soontareya Tower

A scale model of Aurecon's Sooontareeya Tower in Bangkok

Wind Tunnel Studies of Aurecon's Soontareeya Tower

50 year 0 degrees compared to 130 degrees.

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Aurecon's Soontareeya Tower with TMD

How the Digital Wind Method works

The Digital Wind Method starts by capturing the wind flow around a physical model of the building inside a wind tunnel using the most reliable traditional techniques. From there, we journey into the unconventional, by converting the captured wind data into numerous digital wind forcing functions to recreate the along-wind and crosswind effects for the full height of the building.

These forcing functions can then be imported into structural analysis models to allow structural engineers to analyse the real-time behaviour and dynamic response of the building under the various types of wind events, including the assessment of auxiliary damping devices such as tuned mass dampers.

The Digital Wind Method provides the following advantages over traditional methods:

Ability to directly assess the performance of discrete auxiliary damping devices proposed for the building. Traditional wind tunnel testing cannot achieve this because discrete dampers cannot be scaled down and placed in the wind tunnel test model.
Ability to include more advanced structural behaviour such as geometric and material non-linearity. Traditional wind tunnel testing cannot achieve this because these structural behaviours are too complex to simulate in a scaled physical form.
Freedom for the structural engineer to modify the structural framing of the building and re-run the analysis using the same digital wind forcing functions, provided the external building envelope is unchanged. This allows the structural engineer to quickly and efficiently perform parametric studies and optimisation of the structural system without needing to redo the wind tunnel study.

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Into the future for tall, slender buildings

While it’s still early days for our Digital Wind Method, the opportunities it presents are already creating excitement. Aurecon will continue to use our innovation to rapidly prototype wind resisting options and optimise designs for buildings of the future.

With these analysis techniques it means we now have more insights and information than ever before. It gives structural engineers much more control over the dynamic response of buildings under wind events. In the future we will undoubtedly have even more efficient ways of generating digital wind profiles, so perhaps the most exciting part about our new workflow for wind is that this is just the beginning – we are heading into an age of unprecedented levels of digitisation and automation for this work, which will enable us to optimise structures more effectively, creating increasingly complex, slender, less expensive and more efficient tall buildings.

And where to from here? As urbanisation increases, not only are tall buildings increasing in height, at the same time they are also becoming thinner and slimmer as a result of our changing cityscape. To solve these urban problems, Aurecon, as a co-creator of the modern cityscape, is actively imagining what’s next through our collaborative research with leading academics to pave the way for a future of even more daring super tall and super slim iconic buildings.