A 100-storey building is taller than most hills, flexible enough to sway, and yet it can ride out storms and earthquakes with its occupants barely noticing. The engineering behind that combines smart shapes, stiff cores and, in some towers, huge moving weights that fight the motion.
Two very different enemies
Wind pushes on a tall building steadily and in gusts, and it also causes a dangerous side-to-side wobble. Earthquakes shake the ground beneath it, so the building has to absorb and release energy without breaking. Designers must handle both, and the solutions sometimes pull in opposite directions.
Fighting the wind
The problem of vortex shedding
When wind flows past a tall block, it peels off in swirling vortices, alternating from one side to the other. Each vortex gives the building a small sideways push. If the rhythm of those pushes matches the building's natural sway rhythm, the motion builds up, much like pushing a child on a swing at exactly the right moment.
Shape as a solution
Engineers "confuse the wind" by changing the building's shape with height. The Burj Khalifa in Dubai uses a Y-shaped plan that steps back in a spiral as it rises, so the vortices cannot organise into a steady rhythm along the full height. Tapering towers, rounded corners and openings near the top do the same job.
A stiff core and outriggers
Most skyscrapers have a massive concrete core around the lifts and stairs. Outrigger trusses at a few floors connect this core to the outer columns, so the whole building resists bending together, like a person stretching their arms out for balance.
Tuned mass dampers: the swinging giant
Some towers carry a heavy mass near the top, tuned to move opposite to the building's sway. Taipei 101 in Taiwan has one of the most famous: a steel sphere weighing around 660 tonnes, hung like a pendulum. When the tower leans one way, the damper lags behind and pulls it back, turning the building's motion into heat in hydraulic dampers.
Surviving earthquakes
Ductility: bend, don't break
Buildings are not designed to stay rigid in a major earthquake. They are designed to bend and deform in a controlled way, absorbing energy without collapsing. In reinforced concrete, this comes from careful detailing: closely spaced ties in columns, proper anchorage of bars and enough confinement where members join.
Strong columns, weak beams
If anything must yield in an earthquake, engineers want it to be the beams, not the columns. A damaged beam is repairable. A failed column can bring down all the floors above it. In India, the earthquake design code IS 1893 and the ductile detailing code IS 13920 build in these principles.
Base isolation
Some buildings, especially hospitals and important low to mid-rise structures, sit on flexible bearings made of layers of rubber and steel. The ground moves, but the bearings let the building above move much less. Base isolation works best for stiffer buildings and is less common in the very tallest towers.
Lessons for ordinary buildings
Most collapses in earthquakes are not skyscrapers but ordinary buildings with poor detailing, soft ground storeys left open for parking without extra strength, or unreinforced masonry. The same principles of continuity, ductility and good column design protect a three-storey house as much as a supertall tower.
Frequently asked questions
Do skyscrapers sway?
Yes. Tall towers can move several tens of centimetres at the top in strong winds. Designers limit the acceleration so people inside do not feel uncomfortable.
Is a taller building more dangerous in an earthquake?
Not necessarily. Tall flexible buildings respond differently from short stiff ones, and a well-designed tower can perform better than a poorly built low-rise.