Structural Integrity of Towers in General

[base311]

posting this for base626, who seems to be having trouble logging in:

"Concerning structural integrity of towers in general, what are people's thoughts on the number of jumpers that can be on a tower at any given time?

Specifically, with respect to smaller self-supporting towers in the 300-400 foot range, how do you feel about putting 5 to 6 jumpers on them at once? It has been our experience that - with 3 jumpers at the top of a small self-supporting tower - things get rather shaky. What if you were to put 6 guys on there at once?

Also, newer guyed towers seem to be much studier than some of the older guyed towers. In one particular case we have two different 1100' footers. One is rather flimsy and the other rather sturdy. Do you ever worry about a tower collapsing while you're climbing it? What recourse would you suggest if - while climbing say at around 150-200 feet - one of these things decides it's time to collapse?"

-626

end of message posted by-proxy.

bsbd,
Gardner

[steveo]

I have seen hundreds of watermelon sized ice balls at the base of 1000'tower some even smashed through the roof of the small building at the bottom.I bet all that ice put on a scale would weigh more than 10 men.but i wouldnt be surprised if an ice storm a little worse than that one brought it down next time.:-(

[base570]

I think that the structural integrity of the towers is very very good. I agree with SteveO about the huge ice chunks that fall off the things, in fact just the other day I went to one of our towers and one of the awnings was totally destroyed by falling ice. These towers take on tons of weight when ice builds up on them, much more weight than a few people could put on them.
As far as the smaller cell freestanders, we have put 4 on them with no problems... except for the thing swaying a lot. The bigger, beefier freestanders could probably hold 10-20 people, these things are totally overbuilt.

One last note... If the tower decides to fall down while your on it, your most likely dead if your climbing the inside. If your on the outside you might have a chance by pulling high and flying away from falling debris. Of course if your at 200ft. you probably couldn't react quick enough to save your arse.

Peace,
Jason 570

[bandito]

I would agree with Jason about the weight.
What kills towers is normally the wind load.
Think about it...
All towers a designed to withstand X amount of wind load with Y amount of sway.
Many antenna disperse energy in a wide pattern, so the tower can be built cheaper and allow a substantial amount of movemet.
Many micro wave dishes (especially the large ones 6' +,) have a narrow pattern. These are mostly found on rock solid towers.
I aligned two such dishes at the 900' and 1000' levels on a new Pyrod, and I swear this structure NEVER moved!!! Even with 30- 40 mph winds up top!
Of course this tower was built for these dishes.
Many small towers you'll see may have MANY dishes, stick antenna, and or cell arrays. the more crap, the more wind load, the more fatigue and sway.
Of course sane folk wouldn't be found anywhere near a tower when there is ice on it (ice adds weight and mucho grande wind load,) or when the winds are high.

Bottom line, the choice is yours.

Be cool.


Rob

PS A small tower I was on last year came down two months later. No ####.:o

[Mike]

I agree that towers are designed to withstand a significant additional load from icing. However, when icing occurs the increased load is pretty well distributed. When you start climbing one of these things, the load is concentrated at one point. My rule of thumb is to keep jumpers spread out along the tower, and avoid taking breaks at the same spot at the same time.

What worries me the most is when two or more jumpers climb to a certain "platform" and congregate there for ten minutes checking their gear. Sometimes what appears to be a platform is actually just an ice-guard, designed to protect whatever is underneath from falling ice layers. (i.e. not a "maintenence" platform) Sometimes these things are pretty solid, sometimes not.

I've always been interested in the harmonic properties of towers as well, particularly any effect on the natural frequency of the tower sections between the guy wires. I've noticed that dishes and other heavy devices are almost always mounted at or near a guy wire connection. Any thoughts?

[Skinflicka]

I've always been interested in the harmonic properties of towers as well, particularly any effect on the natural frequency of the tower sections between the guy wires. I've noticed that dishes and other heavy devices are almost always mounted at or near a guy wire connection. Any thoughts?

Jen keeps asking me why you don't have a girlfirend. Now I have an answer for her.

I'll explain the wires / load thing next time. I'm horribly drunk at the moment.

Chin chin,

Skin.