Wind, Load, Sway

Wind, Load, Sway

A tall building is a vertical beam stuck in the ground, and the wind is the load.

Gravity is the easy load: it goes straight down through columns. Wind is the hard one: it pushes sideways, gusts, and makes the building sway.

How much. A 300-metre tower may move a metre at the top in a storm. Occupants feel acceleration, not displacement; the design limit is comfort, not collapse.

How it is resisted. Braced frames, shear walls, a stiff concrete core, outriggers to the perimeter columns, tuned mass dampers (Taipei 101's 660-tonne pendulum), and shaping the building so the wind cannot organise itself into vortices.

How it is tested. Wind-tunnel models, pressure taps, and the structural engineer's computer.

The trades. Ironworkers and welders build the bracing; concrete crews pour the core; the industrial-maintenance technician services the damper; the glazier's curtain wall must take the pressure without leaking.

Try it. The sway model on the table: push, and watch the damper answer.