Atlanta's towering cranes get to swing in Irma's winds

That's right - they're spinning on purpose.

ATLANTA - Tropical Storm Irma plays with Atlanta’s construction cranes – spinning them around and rocking them back and forth.

A time-lapse video shows just how much the wind affects the dozen or so cranes towering over midtown.

This same storm – as a hurricane in Florida – destroyed three cranes.

It’s like when you’re driving. If there’s a headwind or a tailwind, pretty much no problem.

It’s that perpendicular wind to the side of your vehicle that can throw you off the road.

Of course, when you’re driving, you have to fight the wind, but when it comes to cranes, it’s actually better to let them swing back and forth. That’s why the crane companies leave the parking brake off during storms.

That’s right – they’re spinning on purpose.

It’s called “weather vaning.”

Notice how they’re all pointing in the direction the clouds are moving?

That means the smallest surface area is facing the brunt of the wind force at any given time.

If these cranes were locked down, they’d have to withstand broadside winds.

You can see how much the cranes are wobbling from side to side – which is concerning, because their footing is only as wide as the spine of the crane itself. The higher the crane, the more torque at the top.

That’s why the cranes are carefully balanced with large counterweights on the short end of the horizontal structure.

Smaller cranes throughout Atlanta were lowered to minimize the danger. But the tower cranes take weeks to put up and take down. There simply was not enough warning – so like the rest of us, they’ll have to weather the storm.

RELATED | After Irma: What to do now

AND | Power out? Here's what to do

© 2017 WXIA-TV


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