Anti-Sway Designs
As our cities become more condensed, our buildings have had to move skyward accommodate us. But with this additional height comes additional problems.
jonathanlei.jpg)
.jpg)
When building skyscrapers, you have to factor in that the wind is significantly stronger higher up. This leads to vortex shedding - a phenomena that is caused by the wind having to flow past these structures, creating swirling vortexes of air. These vortices act as alternating pressure zones and buffet the building back and forth when the vortex shedding frequency reaches the resonant frequency. The result of this is structural damage and discomfort for those inside the building., but there are a number of clever design techniques in place to combat this.
Almost all taller buildings are tapered towards the tops, reducing surface area where the wind is stronger. This can be achieved by adding a point, as with The Shard, or by just having periodic set-backs as the height increases. It also helps to eliminate any hard corners and edges by rounding them off as it makes the buildings more streamlined, allowing air to move around them easier. The same goes for utilising a twisted structure – the spirals redirect the wind upwards and away from the building, resulting in some stunning architecture. One of the most aesthetically interesting design techniques, but also perhaps one of the most simple, is just adding holes in the side of the structures so that the wind travels straight through. In Hong Kong, these gaps in buildings also serve another purpose – they’re dragon gates. It’s believed that invisible dragons live in the mountains and like to fly down to swim in the water off the coast. The city’s enormous buildings block their paths and anger them, resulting in bad luck for the citizens. They’re a great example of feng shui, a concept that is taken very seriously throughout Hong Kong.
The final technique used to reduce wind damage is damping. Slosh tanks filled with gallons of water can sit in the top of buildings and slosh back and forth, counteracting the swaying motion. Then there are tuned mass dampers, enormous weights which hang in the centre of the building and stabilise the harmonic vibrations. In previous years, these were always hidden away, working quietly behind the scenes, but now the world’s heaviest and largest tuned mass damper is suspended between the 87th and 91st floors of Taipei 101 in Taiwan and can be visited by tourists. In this way, the damper has become an aesthetic feature of the building rather than just a piece of technical equipment.
![taipei-101-damper-6[6].jpg](https://static.wixstatic.com/media/5f4c6a_a25a5d9a605c4bd3afdea9bf7d53f81d~mv2.jpg/v1/crop/x_0,y_0,w_770,h_524/fill/w_451,h_307,al_c,q_80,usm_0.66_1.00_0.01,enc_auto/taipei-101-damper-6%5B6%5D.jpg)
In adding these features to our buildings, engineers and architects have had to come together to create structures that are stable, but also beautiful. The skyscrapers of Dubai are stunning to look at, but this beauty has stemmed from basic engineering principles that we learn early on in our careers. As our buildings have increased in height, it’s interesting to see how this has brought their anti-sway mechanisms to the forefront of their appearance, balancing their functionality with their aesthetics. In this way, simple engineering techniques have influenced what is considered modern, and even fashionable, in the field of architecture. As discussed in my previous blog post, great design works in tandem with engineering, and when done right, the results can be spectacular.