Engineers have developed a new way to protect tall buildings from strong winds and earthquakes by allowing some floors to move rather than trying to keep the entire building rigid.
The idea, inspired partly by the behavior of traditional Japanese pagodas, uses the building’s own weight to control swaying.
Researchers from Imperial College London and engineering firm Arup say the approach could make skyscrapers safer and more comfortable while reducing the amount of concrete and steel needed for construction.
The research was published in Nature Communications.
Tall buildings naturally sway when exposed to strong winds. They can move much more dramatically during earthquakes. Traditionally, engineers have tried to make buildings as stiff and strong as possible, which can require large amounts of structural material.
Some skyscrapers also use devices called tuned mass dampers. These are enormous weights, sometimes weighing hundreds of tonnes, installed near the top of a building. When the tower sways in one direction, the weight moves in a way that helps counteract that motion.
While effective against wind-induced movement, these systems take up valuable space and require additional structural support. They also provide limited help with the forces generated by earthquakes, meaning buildings in earthquake-prone areas may need additional protective systems.
The Imperial and Arup team wondered whether they could use something already present in every skyscraper: its floors.
Their design separates several usable floors near the top of a tower from the building’s central structural core. These floors are connected to the core using springs and dampers, allowing them to move slightly and independently.
The floors effectively become part of the building’s vibration-control system. Their own weight helps absorb energy and reduce the movement of the tower during high winds or earthquakes. Importantly, the floors can still be used normally by occupants.
To test the idea, researchers built a 1:300 scale model representing a 300-meter-tall skyscraper. They tested it in a large wind tunnel at Imperial and also conducted experiments simulating earthquake conditions.
The results were striking.
Compared with a conventional rigid tower, the new system reduced peak accelerations caused by wind by as much as 71%. Forces at the base of the building, known as base moments, fell by more than 50%.
During simulated earthquakes, movement at the top of the tower decreased by an average of 42%. Movement within the specially designed movable floors was reduced by as much as 74%. The relative movement between these floors and the building’s core was small enough that occupants would not normally notice it.
One major advantage is that the same system can protect buildings from both strong winds and earthquakes. This could be particularly useful in cities that face both hazards, including Hong Kong, Manila and Taipei.
Because the design uses existing technologies such as springs, dampers and bearings, the researchers believe it could be introduced without dramatically increasing construction complexity.
Reducing the forces acting on a skyscraper could also allow engineers to use less concrete and steel in its core, columns and foundations. That could lower construction costs as well as the carbon emissions associated with producing building materials.
The researchers are now planning larger-scale tests and hope to eventually demonstrate the technology in a real building, potentially offering architects a new way to create taller, lighter and more resilient cities.
