Hacker News Reader

Comment by qikInNdOutReply | Hacker News Reader

Stupid question: If you had sensor good enough, could you build active structures, that anticipate the forces of the wind and angle themselves to "lean" into it, neutralizing the forces at play?

View on HN

More commonly you'll see things like tuned mass dampers (https://en.m.wikipedia.org/wiki/Tuned_mass_damper) to try to reduce the amplitude of the swaying from wind, earthquakes, elevator vibrations, etc.

So giving this a push, that cancels wind forces out..

No, you don't have to give it a push. You just leave it hanging there and inertia and resonance do the rest.

You would then have to add mechanical devices, which would likely be heavier (requiring even more support structure strength), that would have to move hundreds or thousands of tons of building mass, and with high precision, and then return it to the initial position, while canceling the inertial forces to prevent it from ping-ponging and making it worse. I only have basic engineering knowledge but I can almost hear one of my professors screaming, 34 years later. :)

Many tall buildings have a tuned mass damper near the top that helps to dampen oscillations. It doesn't require any active mechanical devices. Taipei 101 has it out in the open, you can easily find videos of it during earthquakes.

We are already doing that. Most of these very tall structures have mass dampers, huge weights which are manipulated to compensate the swing induced by wind or ground movements.

That's 1-not active, 2-doesn't compensate, but dampens

Tuned mass dampers don’t but active mass dampers do. Both are in use.

Also damping is achieved by dissipating energy through the counter mouvement of the tuned mass which is literally compensating for the movement put in place by the external force. It doesn’t totally offset it but still.

I don't see a problem with anticipation i.e. detect the prevailing forces and apply an equal but opposite force.

I DO see a problem with making the strength on each corner of a building dynamic - if you aren't moving the building back and forth to counter the wind, how would you counter the wind?

One option (almost certainly not practical) would be to have the building shaped like a giant vertical wing, and have it rotate into the wind. It could be tuned to be resistant to wind forces by directing it around, but the apartments may face a different way each day.

Hah, a bit like the roof of an oast house. I like it.

> One option (almost certainly not practical) would be to have the building shaped like a giant vertical wing,

Like a weathercock?

Well, dunno about anyone else, but I'd jump at the chance to live in a (safe) building that always rotated to face the wind.

I originally thought more along some pneumatic nuzzles, basically like direction controll nozzles on a space ship capsule

You really, _really_ do not want a skyscraper that collapses if the latest Windows update has a regression.

(I mean, I'm being slightly facetious, but in general things which will kill thousands of people if there's a bug... well, you should be cautious)

This is already accomplished passively with tuned mass dampers.

Reply on news.ycombinator.com