Heated and Bent Anchor Rods

[NWK]

For those of you having to remedy a contractors lack of quality control, here is a question for you:
I am a new structural engineer left to research a current anchor bolt problem we are having. The contractor failed to insure the 22 inch long, 1 inch diameter anchor rods were plum before concrete hardened. The exposed 5 inches of rod were not able to accept the base plates due to their angle. Construction workers decided to torch heat the tops and bend them back straight. This not only left scortched threads on the anchor rods and a glassy concrete surface, but most likely affected both the steel and concrete pedestal's material properties. The contractor is not worried about the issue, but as engineers it is our duty to address questionable areas such as these. A load test has been requested on anchor rods having this "straightening" performed on them. The test has not yet been performed, but things are heading in that direction.
Has anyone experienced a similar problem? How are the materials properties affected by this heating and bending? Is a load test the best answer to the problem? I am not familiar with load testing, but to provide a straight tension pull it seems as though the equipment might be fairly large sized to avoid bearing on the pedestal. Any help on this matter would be helpful and greatly appreciated. Thanks.

 

[ljr]

depends upon the type of steel used for fabricating the anchor bolts. If the steel has alloying elements present (High strength steel usually has) then you have a problem. If the anchor rods are mild steel then you will probably be ok.

 

[NWK]

The designer has informed me that the unfactored loads on each anchor rod is 21 kips. The anchor bolts are Quenched and Tempered and apply to ASTM A449. Many anchor rods throughout the project have been tampered with, but in this particular case they are imbedded in an incorrectly formed pedestal without proper edge distance. The footing will be removed and rebuilt for sure. Because it is being removed, it was suggested to perform the load test on these bolts. The allowable load on each rod is 31 kips. Therefore, it was suggested to test them to 26 kips, the average. If it reaches this level, the test will be stopped. If it snaps prior to this, the heating and bending had ill effect. Most likely, due to unproper edge distance, the concrete will fail prior to the anchor. This is a large steel framed-structure designed with shear lags in the perimeter columns. This is new terminology to me, being a young engineer, but the structure is a large open hanger-type building.

 

[dik]

If they're quenched and tempered, I would suggest that they've seen their useful life; it's the heat treatment effect on the alloy that provides their strength. Might need to consult a metallurgist and see what the impact on fatigue, etc. might be; Proofing the bolts is valid approach because it's a messy repair.

If it's a large open hangar type building, then it's possibly a pre-engineered metal building and you might want to check with the supplier/manufacturer to see what the impact on any warranty might be. They often supply the AB's. In these areas the design of many of the pre-eng buildings is pretty tight and the design loadings often have a minimal design for opening related wind pressures and the uplift forces may not be conservative.

 

[LPPE]

Are the bolts in tension or compression? If they're just typical column anchor bolts, they're basically there just for erection purposes. Once the column is in place and the column is solidly grouted under the base plate, then the axial loads should transfer through the plate to the grout to the concrete foundation. I've seen many anchor bolts out of alignment (either from poor placement, or hit with construction equipment later, etc.), and usually bending the bolts back or adjusting the holes in the base plate is enough. Again, this is only if the column is just for gravity loads only. Then again, why would this post be in Moment Frame Engineering if it wasn;t part of a frame. Sorry, disregard this post!