Bending A307 Anchor Bolts 1

[jrfroe]

Can A307 anchor bolts be bent, without a significant loss of strength? If there is a loss of strength, is it safe to use a portion of the full strength? The contractor installed several anchor bolts crooked (10-15 degrees from vertical). The anchors are 1.25" dia x 12" long cast-in anchors loaded in both tension and shear. If we can't use the anchors, I'm thinking about having the anchors cut off, drill new holes through the base plate, and install epoxy anchors instead (luckily the base plate is large enough to do this).

 

[UcfSE]

I wouldn't bend an anchor that large and short. I'd go for replacements.

 

[jrfroe]

Actually, I was mistaken... The length of the anchors are 18" (embedded).

Are you be worried about failing the concrete while bending? If I'm not able to use the strength of the anchors, I was hoping to still allow them to bend some of them straight, just for erection purposes, so they could set the base plate down on leveling nuts, then grout, then drill and epoxy the new anchors.

 

[UcfSE]

I would be worried about changing the way the load is transferred to the concrete, plus the strain you will have to induce in the bolt to get it to bend that much. It seems that might cause a crack or embrittle the bolt. You wouldn't want them to set the column weight on there and have the bolt break, especially if they drop the column on it. That's asking for an OSHA problem.

I could just be too conservative on this, but it sounds like a bad idea to me. If they drill some new holes or slot the existing holes, they will be able to make a template to located the epoxy anchors and just install them in the right place. Perhaps the holes can be slotted enough to get the column in place and allow new holes and anchors to be drilled. That would require you to size a welded washer to transfer the loads to the base plate since the holes would now be too big.

At some point it comes down to "you're just going to have to pay attention and do it right this time". I don't know why everytime a contractor screws up, it's up to us to fix it. If we screw up, they're on us like flies on...

 

[DRC1]

Another option is to use the anchor bolts as is. Slot the base plate holes, drop over the bolts and cut plates to drop over the top of the bolts. Weld the new plates to the base plate & paint. Use beveled washers under the bolts. A little bit of luck and it may look like it was all planned.

 

[unclesyd]

From my buddy in the fastener business.

Make sure you can use multiple washers under the nut. Very recently in my area construction on a large structure came to a halt as it was taking two beveled washers to get the nut bearing area flat. Without the doubling of the washers the nut face was at an angle to base plate and trying to straighten the anchor bolt. The angled anchor bolts were all made and additional anchor bolts were epoxied in. The angle bolts were 1 1/2" dia and 2" dia. Some credit was given for the angled bolts so the additional bolts were smaller due to problems with getting holes in the base plate and concrete.

 

[jwright81]

Seems to me that if you tried to heat the bolts to strighten them, they would become brittle. If you could find a good welder, you could install washers at the bolts, then slot the holes in the plates.. Put the column down over it and put washers and the nut on the bolt. You would have to weld something to void space between the bolt and the nut... That seems more labor intensive than just telling the contractor to eat the cost and install new epoxy grouted anchors..

 

[JStephen]

I would be inclined to try to rework the attachment to fit the bent bolts. You should be able to take your design uplift and shear and resolve them into forces parallel and perpendicular to the bent bolt and show that the bolt capacity is still okay (or if it isn't, you'll know you don't have a choice). If there's some sort of cobbled-together arrangement to make things work, I'd rather have it where I could see it, than buried in the concrete.

 

[connect2]

you could always see how many anchor bolts are actually required for the loads ??? and then go from there, OSHA it assumed being satisfied.