[TowerTalk] Anchor Bolt Grade Suitable for Tower Base?

[Joe Giacobello]

Gentlemen, many thanks for your kind assistance. Frankly, the range of 
advice ranged from common steel is satisfactory to high strength steel 
(grade 5 or the like) would be safer.  I also talked to an engineer at 
Valmont.  (BTW, one class of their 1-1/2" anchors was equivalent to A307 
spec material.)  Nevertheless, he was reluctant to say that the common 
threaded rod would be suitable without a structural analysis.

Finally, I got a hold of Carl Tashjian, current proprietor of Tashjian 
Towers and former engineer for Tri-EX.  I described the base plate and 
installation plans and asked what grade of steel would be suitable for 
the anchors.  He said without hesitation "A307."  So I'm sticking with 
what I have already.  However, I've asked the supplier to find out 
whether the manufacturer is domestic or Chinese.

Thanks to all!


73, Joe

Jim Lux wrote:

>At 09:18 PM 9/13/2005, Richard (Rick) Karlquist (N6RK) wrote:
>  
>
>>>I am installing an LM-470 and prefer to use a base plate for the tilt
>>>base that was designed for retrofit to an already existing concrete pad
>>>and anchor bolts.  The base plate takes three 1-1/2" anchor bolts, which
>>>will be 27-36" long.  I have purchased 10 feet of 1-1/2" threaded rod
>>>that meets ASTM specification A307A,B or C.  Apparently, the stuff is
>>>known as "common" threaded rod and is the lowest strength available.  Is
>>>this rod suitable for this application?
>>>
>>>Tnx and 73,
>>>
>>>Joe
>>>K2XX
>>>      
>>>
>>It seems to me that the strength of the concrete limits the safe load
>>you can put on anchor bolts to a low enough value that ordinary steel
>>is good enough for the bolts.
>>    
>>
>
>
>I was chatting with a structural guy a few months ago about things like 
>chemical anchors for patio covers and the like (a low load 
>application).  Turns out that "taint necessarily so".  The problem isn't so 
>much the strength of even crummy grades of steel, even aluminum rod would 
>be strong enough from a materials point of view. The problem but the 
>uncertain quality of manufacturing in the threaded rod or bolts.  Things 
>like voids, cracks, or inclusions can raise problems because they cause 
>stress concentrations.  When Home Depot goes to the "lowest backyard forge 
>bidder" in a third world country (or more properly, some consolidator who 
>contracts with dozens of these little manufacturing plants) you run the 
>risk that they just dump any old steel from the ship breaker in India into 
>the melt, then rolled out the rods, rolled the threads, dumped it into the 
>plating bath, and loaded it into the container.  Unless the rod actually 
>fell apart coming out of the machine, it's unlikely it was ever really 
>checked.  They literally cannot afford to do any process controls or 
>inspections.
>
>You could either buy cheap stuff and inspect the heck out of it (something 
>most hams don't have the equipment or patience for) or spend twice as much 
>and get something that comes with the process controls and source 
>inspection. (not saying that there's not bogus junk out there, and outright 
>fraud, but it's less likely)
>
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