Short Anchor Bolts

[BearcatEngineer]

I have a situation where the anchor bolts for a sign structure were set too short and with the sign fully erected, the bolts are 2-3 threads short of the top nut. Is it possible to correct this without demo of the foundation and resetting anchor bolts and pouring another foundation.

 

[mrMikee]

Try this, a similar thread:

thread507-129232

-Mike

 

[crossframe]

Check out the bost specifications. I seem to remember that even 2-3 threads shy of flush was acceptable in some situations.

 

[structural01]

You could add a coupler to extend the anchor. If it's only 2 or 3 threads short, I would plug weld it.

 

[UcfSE]

Try thread725-105963 also. Remember not to weld your bolts unless you specified weldable material.

 

[jjeng2]

The AISC Seminar "Field Fixes" covered this and I still have the noted from it. They listed five solutions.
1. Extend by Welding a Threaded Rod
2. Use a coupling nut
3. Weld Base Plates to Rods(dont use on high strength rods)
4. Cut AB's and drill and epoxy new ones
5. Perform analysis on nut using "threads engaged"

 

[SlideRuleEra]

I have not looked into the details at the attached links, but this AISC Steel Interchange Question/Answer

http://www.aisc.org/MSCTemplate.cfm...tomSource/Faq/SteelInterchange.cfm&FaqID=2059

says that this "NASA Fastener Design Manual" offers a way to compute the capacity of the existing situation

http://gltrs.grc.nasa.gov/reports/1990/RP-1228.pdf

Looks like a handy publication to have around anyway.

http://www.SlideRuleEra.net

 

[promaxaccess]

Hello, your problem is not new or unique. I come from a steel erecting background and often faced `Short` HD bolts. Our solution was to overdrill the base plate and use a TEE shaped nut which effectively extended the thead down into the base plate area. You should never weld bolts to bases etc.

 

[Tomfh]

I am a new engineer with little experience yet I have heard of this problem a half dozen times already. The boys must have real trouble getting those anchor bolts to sit right.

One of my lecturers, who has extensive practical experience, swore by epoxyied HD bolts for this reason.

What are all your opinions of epoxying instead of cast in? Some of my more experienced colleagues do not like the epoxy approach as the driller can end up hitting the main reinforcement...

 

[BearcatEngineer]

I appreciate all of the responses. The sign mfg. told me they usually weld the nuts on if requested, but they are hardly ever asked to do this in this situation. Sounds like someone isn't doing their job.

Thanks to all!