Determining Existing Strength of 40+ yr Old Anchor Bolts
Determining Existing Strength of 40+ yr Old Anchor Bolts
(OP)
I have a project where we are adding equipment to an existing structure and need to check that the existing anchor bolts work. The structure is 40+ years old and the existing drawings show that A490 anchor bolts were used.
We don’t think that material was possible at the time, so we don’t think that high strength bolts were used, but the owner doesn't have any records on the anchor bolts installed.
We checked the existing loading conditions of the structure and high strength anchor bolts are required to resist the loading. Since we are adding load, we are not confident that the existing anchor bolts will work.
Is there a way to determine the strength (or material properties – i.e. A36, A307, etc) of an existing anchor bolt without destroying the bolt?
We don’t think that material was possible at the time, so we don’t think that high strength bolts were used, but the owner doesn't have any records on the anchor bolts installed.
We checked the existing loading conditions of the structure and high strength anchor bolts are required to resist the loading. Since we are adding load, we are not confident that the existing anchor bolts will work.
Is there a way to determine the strength (or material properties – i.e. A36, A307, etc) of an existing anchor bolt without destroying the bolt?





RE: Determining Existing Strength of 40+ yr Old Anchor Bolts
At the same time, be ready to provide a "Oh crud, they are not strong enough (or the tested anchor bolts broke out at 50% of their assumed strength) and all have to be replaced" solution.
Thus - First visually inspect each anchor bolt (assign them a unique ID number on each anchor leg location). Surface rust probably OK, but note it anyway. Deep crusted rust, tearing, bending, obviously scrap already, deep corrosion, visible damage. (Bent, distorted, run over by twelve forklift truck wheels.)
Then, pull test every bolt at 50% "design" capacity. If you cannot get a nut and pull test adapter onto every anchor bolt (bad threads, no room, etc) that is itself an indication you need to replace bolts.) If all pass, go to 90% intended capacity.
If all pass, then they will probably accept 100% intended capacity, but you don't know reserve margin. If 10 or 25% fail at either, then you need to start over with new foundations. While looking at how to survive with the current tank or vessel.
RE: Determining Existing Strength of 40+ yr Old Anchor Bolts
Some of the anchor bolts holding down our equipment in indoor powerplants of that vintage have rusted to pencil necks. They are fairly well protected as they go thru raised, poured housekeeping pads. Don't know if the corrosion is from decades of washdowns, or just because coal is evil.
Your first tension test will expose those.
Is it worth moving right to new anchors offset by a few diameters, or via clamps?
http://www.plastics007.com/upload/Product/Image1/P...
RE: Determining Existing Strength of 40+ yr Old Anchor Bolts
http://www.ge-mcs.com/en/hardness-testing/uci/mic-...
RE: Determining Existing Strength of 40+ yr Old Anchor Bolts
RE: Determining Existing Strength of 40+ yr Old Anchor Bolts
RE: Determining Existing Strength of 40+ yr Old Anchor Bolts
I refuse to use 'rebound hardness' testers for anything other than point-to-point comparisons. Never, never has one of these testers given me anything approaching a valid hardness reading in 'the field'. They just do not work, even though they calibrate just fine on the perfectly machined test coupon supplied with the tester. If you choose to use one of these devices, please just use it for direct item-to-item comparisons. Get some nonshrink grout, an A490 bolt the same diameter and similar length, and a steel bucket. Embed that bolt in a bucket of grout, with the same amount of threads above the concrete. Use that as your comparison specimen. Ron is right, it is indeed possible that those embeds are A490's. I'll bet you a virtual drink at Pat's Pub that they are not, but the possibility needs to be investigated.
RE: Determining Existing Strength of 40+ yr Old Anchor Bolts
It will not tell you is the bolt is cut, bent, rusted, deformed or actually (strongly) embedded in the old concrete - A piece of otherwise good metal wobbling loosely in a cracked, oblonged hole that has been vibrating for 3-13-33 years will pull out as soon as it is loaded. A bent old anchor bolt with rusted off threads cannot be re-used, regardless of what steel it was originally made of.
RE: Determining Existing Strength of 40+ yr Old Anchor Bolts
The problem gets tricky because the anchor bolts are 1 3/8" dia, 7 feet long for a dead end transmission tower - that is loaded. The new equipment weight is negligible but the original line loads have increased and we have been tasked with checking the structure. The check has revealed that high strength bolts are needed; which is why we wanted a way to check them.
RE: Determining Existing Strength of 40+ yr Old Anchor Bolts
RE: Determining Existing Strength of 40+ yr Old Anchor Bolts
Remove a representative sample or two and obtain a full diagnostic profile: metallurgical condition at core and thread root (structure, Vickers hardness), a profile assessment to confirm dimensional conformance and to find any deleterious forming defects, chemical analysis (actual, NOT PMI), and examination of the surface for corrosion pitting.
Grout integrity is a whole nother can of worms.
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Determining Existing Strength of 40+ yr Old Anchor Bolts
Since the anchor bolts have been encased in concrete for 4 decades, I don't think a hardness check of just the head would be sufficient. There could be corrosion of the surfaces just below the head which are typically areas that are highly stressed. Since you are apparently on the hook for signing off on the engineering of this modification and there are no reliable records of the legacy installation available, I imagine you would want to ask to replace every fastener. And if the customer does not agree, get someone else to sign off on the engineering.
RE: Determining Existing Strength of 40+ yr Old Anchor Bolts