With real estate at a premium in major cities like London, developers are keen to maximise the construction potential of land with tall, thin buildings. Tall skyscrapers require tuned mass dampeners (TMDs) to resist wind and earthquakes however. TMDs can weigh up to 1,000 tonnes and span five storeys in a 100-storey building – adding millions to building costs and using up premium space in tight city centres.
Researchers at City, University of London, are developing devices based on Formula 1 technology that could massively reduce TMD weight and enable thin, tall buildings that are nonetheless wind- and earthquake-resistant.
‘Adaptive vibration suppression devices’ installed at the top of buildings would combine inerters similar to those used in suspension systems of Formula 1 cars with TMDs, which work like giant pendulums to counteract building movement.
The inerters have gearing for varying apparent mass. They could gear up to minimise floor accelerations during high-occupancy hours, and then gear down to harvest energy from oscillations caused by wind during low-occupancy hours.
Lightweight and compact inerters could reduce the required weight of current TMDs by up to 70%, said the researchers, led by structural dynamics expert Dr Agathoklis Giaralis.
Dr Giaralis said: “If we can achieve smaller, lighter TMDs, then we can build taller and thinner buildings without causing seasickness for occupants when it is windy. Such slender structures will require fewer materials and resources, and so will cost less and be more sustainable, while taking up less space and also being aesthetically more pleasing to the eye. In a city like London, where space is at a premium and land is expensive, the only real option is to go up, so this technology can be a game-changer.”
A typical 20-storey building using the devices would require up to 30% less steel in its beams and columns, said the researchers. Computer model analysis for an existing London building, the 48-storey Newington Butts in Elephant and Castle, reportedly showed that floor acceleration – the measure of occupants' comfort against seasickness – could be reduced by 30%.
“This reduction in floor acceleration is significant,” said Dr Giaralis. “It means the devices are also more effective in ensuring that buildings can withstand high winds and earthquakes. Even moderate winds can cause seasickness or dizziness to occupants and climate change suggests that stronger winds will become more frequent. The inerter-based vibration control technology we are testing is demonstrating that it can significantly reduce this risk with low up-front cost in new, even very slender, buildings and with small structural modifications in existing buildings.
“As well as achieving reduced carbon emissions through requiring fewer materials, we can also harvest energy from wind-induced oscillations – I don't believe that we are able at the moment to have a building that is completely self-sustaining using this technology, but we can definitely harvest enough for powering wireless sensors used for inner building climate control.”
The research was published in the November 2019 issue of Engineering Structures.
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