How can I prevent vibration of metal structure in wind?

In article , Englishman in Adana (Turkey) writes

This tubular vibration/oscillation once bought down a TV mast at Emley moor near Huddersfield in order to stop it happening again the mast owners ntl at the time, used damping chains hung inside the tubular towers.

Quite drastic but its worked very well, and seeing that some of them are at 1265 feet high!....

If the idea is to break up the airflow around the bars, foam-type pipe insulation is overkill - and ugly, as a permanent solution. It might be a cheap way of checking that this is the right solution to the problem, though.

At first I thought you were right. However I then thought if I had a 1cm steel bar 50cm long and clamped in a vice what sort of 'twang' fequency might I expect and I think it would be audible and fairly lowish.

So I think we could be looking at a self induced vibration. I guess anything that breaks up the air flow - especially in the middle third of the bar would work.

Possibly not. Rather the bars cause the air to form pressure waves of audbile frequency.

Is this not the same problem they a have with tall chimneys oscillating in the wind?

The solution there is a spiral fin that is wrapped round the chimney that breaks up the air flow round it, and stops the wind turbulence from being able to reach the resonant frequency.

Alternatively simply adding some damping to the bar will change its resonant frequency - hence different damping on each bar will at least prevent them all singing at once!

For example: Building regs, Approved document K section 3.3:

"Where buildings are likely to be used by children under 5 years the guarding should prevent children being held fast by the guarding. The construction should ensure that a 100mm sphere cannont pass through any opening in the guarding and so that children will not be able to climb it. Horizontal rails for such guarding should be avoided"

While this might be the case and I'm not disputing it is not, but have you seen some of the waterfront/docklands apartments in and around the uk 2/3 bedroom flats with verandas/balconys...guess what! some them have horizontal bars up to waist height.

Hmmm! how did they pass the safty regs?

-- Sir Benjamin Middlethwaite

perhaps by arguing that they are not "family" accomodation and hence little chance of kids climbing on them...?

I see, so its a...leave you're kids at home if you are coming to visit us. :-)

-- Sir Benjamin Middlethwaite

Wasn't the OP in Turkey? Maybe they have different regs!

Grumble

|This tubular vibration/oscillation once bought down a TV mast at Emley |moor near Huddersfield in order to stop it happening again the mast |owners ntl at the time, used damping chains hung inside the tubular |towers. | |Quite drastic but its worked very well, and seeing that some of them are |at 1265 feet high!.... | |

Yes but they did experience severe oscillation or all of the tubular designs at various times and had evacuated them on several occasions. Notable Winter hill (Lancs) and (Belmont Yorks)

Do try and include MrRumms statement about the building regs for this country and then you will get genralisation it was UK we where on about.

-- Sir Benjamin Middlethwaite

I was going to say that - several small bungees stretched tight at random heights between different bars might break up the resonance.