[TowerTalk] Fwd: Achor bolts?

[jimlux]

On 3/24/18 11:47 AM, Hans Hammarquist via TowerTalk wrote:
> 
>   Well Jim,
> 
> With a working force of 10 000 lb and a pull-out force of 15 000 to 28 000 lb gives you a safety margin of 1.5 to 2.8. Would you trust that?
No, but you'd se more than one bolt.

Dynamic loads shouldn't make any difference as long as the bolt is 
always under tension (so the nuts don't come off) - I don't think these 
loads are high enough for fatigue to be an issue. Interestingly the 
pullout force might be higher than the bolt strength.  15,000 lb on 0.2 
square inch is 75,000 psi.




> 
> What I remember from my engineering school time you need a safety factor of 4 - 8 to trust a structure, 4 for static load and 8 for dynamic load. You have to include fatigue etc. I am not talking about the fact that bolts corrode over time. Is a tower static or dynamic load? There are probably no vibrations of any significants but varying wind would probably put it in the dynamic category.
> 
> Hans - N2JFS
> 
>   
> 
>   
> 
> -----Original Message-----
> From: jimlux <jimlux at earthlink.net>
> To: towertalk <towertalk at contesting.com>
> Sent: Sat, Mar 24, 2018 11:31 am
> Subject: Re: [TowerTalk] Achor bolts?
> 
> On 3/24/18 6:34 AM, Hans Hammarquist via TowerTalk wrote:
>> Dear towertalkers,
>>
>> The are claims in a discussion on Face Book that an anchor bolt, "5/8 in. x 12 in. Hot-Galvanized", is suitable for a free standing tower. Someone even claims it is used for a 400' freestanding tower. It doesn't make sense to me but I might be overly pessimistic.
>>
>> I hate to start lengthy discussions and this might be one of them so, please, comment only if you have a well grounded answer. I'm sure there are plenty of opinions about it like my own, but I would like to know if my guts feeling is right or wrong. What I am afraid of is that you can pull out an anchor bolt like that right out of curred concrete.
>>
> 
> There are standard "pull out force" tables for chemical anchors (bolts
> epoxied into concrete)
> 
> Looking over some catalogs, it looks like the standard embedment length
> for 5/8" is in the 7-9" range.   Pull out ranges from 15,000 to 28,000
> lb, depending, it seems, mostly on the concrete (because typically, the
> adhesive is stronger than the concrete)
> 
> So how much force are you putting on those bolts in your freestanding
> tower? 100 lb at the top of a 100 foot tower is 10,000 ftlb moment, and
> if the tower is 1 foot wide, that's 10,000 lb load on the upwind bolt.
> So, the bolt would hold.
> 
> 
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