bent anchor bolts

[doka1]

I am a foreman for a concrete contractor on a 5 story steel structure building. The steel is being erected with 3/4" f1554 gr 55 anchor bolts. During the installation of the underground plumbing the plumbing contractor bent several anchor bolts. Of course bolts were bent to different degrees, one was sheared about 2 inches from the base, 3 were bent to the ground (runover), and about 10 were just bent. Having delivered the project with all anchor bolts intact, our position as always in such situations, is that it is not our responsibility for the repair of the bolts. We further expressed to GC that in such situations there are a number of repair procedures that must and should be followed. Without further information from the EOR we could not proceed on correcting the situation.

The GC did as we suggested and submitted an rfi regarding the situation, and added in the rfi the suggested fix was to core the bolts and epoxy new anchors as the anchor bolts are in fact in the right location. The EOR's replied agreed with the suggested repair and stated that any bolt bent any more than 45 degrees should be cored and epoxied.

When asked to begin work on the repair we reviewed with the GC the potential problems with such a procedure. The inability to oversize the core more than 1.5" and damaging rebar as some are in pedestals. Nonetheless, the work was started. Before coring any bolt we attempted to straighten each bolt. We did not apply any heat, and bent only about 5 degrees at a time, with rests between each bend slight bend of the rod. We were able to straighten out 11 of 14 bolts, and none of which showed signs of stress or cracks from being bent.
The GC would still like to see all the bolts the be cored and epoxied as they do not want to the deviate from the EOR direction. I stressed my concerns that we may be doing more harm than good by replacing all the bolts considering some stirrups and column steel may be cut during coring. Furthermore, all bolts are 3/4" which are typically for erection purposes only, so is it really necessary to go to such lengths. It does seem odd that a 5 story building to have only 3/4" anchor bolts, but I must mention the building does have a lot of steel bracing, this certainly has something to do with the sizing of the rods, correct?

In summary, I am just looking for some feedback on whether or not bolts bent more than 45 degrees can be salvaged. I understand that there are a lot of variable to determine whether or not this is possible, ie whether or not the bolt is in tension.

My issue is that the GC is taking an easy approach to the engineer's direction. I dont feel the engineer has fully analyzed the situation and understands the consequences or the feasibility of the repair. I feel the GC should suggest another option like welding (is that ok on f1554 gr 55?, or even offsetting a hole in the baseplate.

Your comments are appreciated!

 

[BAretired]

From Portland Bolt:

http://www.f1554anchorbolts.com/faq.php

It depends on the grade. F1554 grade 36 is mild steel and is weldable. Grade 55 is a modified mild steel and is weldable, provided it meets the weldability requirements as described in Supplementary Requirement S1 of the F1554 specification. Grade 55 material that does not meet the S1 carbon equivalency parameters is not weldable. Grade 105 is not weldable since the heat generated during welding could alter the mechanical properties of the medium carbon alloy quenched and tempered material.

If the steel is weldable, the best option (in my opinion) is to cut off severely bent anchor bolts and weld extensions on them. If it is not weldable, you may have to core. In any case, the EOR must agree before proceeding with the work.

BA

 

[connectegr]

In most cases your anchor bolts are hardened material, and should not be welded. I don't have it in front of me, but AISC Design Guide 1 provides guidelines and suggestions for repairing these conditions.

http://www.FerrellEngineering.com

 

[doka1]

Do you think it is too risky to leave the straightened anchor bolt??? Especially considering the bolts may not be in tension.

 

[ToadJones]

I'd look into DG1 for suggested repairs.
I recall seeing "couplers" (lack of a better term) on bolts whose project was too short. Maybe you could remove enough concrete to use a coupler

 

[connectegr]

Ultimately that is up to the EOR. Any alternate should be reviewed and approved be the EOR. A post-installed epoxy anchor may not be equivalent to the original precast anchor. This is really not a decision for the GC. Bent or damaged anchors are common. As I noted before AISC Design Guide 1 has some information. It is available to download on the AISC website. Photos might be helpful.

http://www.FerrellEngineering.com

 

[dik]

Can you have the mechanical contractor provide an engineered solution for the EOR?

Dik

 

[chicopee]

Sounds like a sloppy jobsite to me. Are mechanical connectors avaible for anchor bolts?

 

[csd72]

The aisc has a webinar called 'field fixes' which has a lengthy section on anchor bolt repairs.

The repair really depends on the loads applied to the anchors. For tension capacity I have applied angle or plate 'straps' over the base plate with a chemical anchor at each end. I have never actually asked them to core out the existing and replace.

I would be concerned about the fatigue strength of the rebent anchors both in shear and tension.

 

[Forensic74]

They must have used gr55 bolts for a certain reason. If you bend over a gr55 bolt 45 degrees it's pretty much worthless. You've already yielded most of the bolt. Bending it back 5 degrees at a time makes no difference, the damage has already been done.

doka1, I feel your pain, but I hope you understand that you have no clue to how much force is going into those bolts. It all depends on the specific layout of the building. Honestly, a 2 minute call to the engineer with a productive attitude would probably accomplish more than anything.

 

[doka1]

MainMan10, you're absolutely correct, a 2 minute call would probably resolve the situation both cost effectively and correctly.

I am going to suggest two methods to choose. Assuming rod is weldable cut extension at 45 degrees and weld. AISC has procedure for this.

Secondly,as csd72 suggested, assuming edge distance can be maintained in pedestal, drill a hole outside the baseplate and use an angle or heavy plate over baseplate. there is enough projection on the other bolts that it would be able to receive this heavy plate/angle

Everyone's concern about the fatigue of the bolts really answered the root of the question...

 

[dik]

Is the specified steel weldable... Grade 55, in F1554 can be weldable.

If it is, then the repair may be as simple as cutting the concrete down a bit to expose 'good' rod, and welding a new threaded extension to it... If not weldable, then it's a matter of coring and glue... Also should be talking to the EOR about what he would consider as a suitable remedy.

Dik

 

[JAE]

I would recommend welding on extensions provided the Gr 55 bolts have the supplement 1 - weldability included in the spec. Research this with the supplier and pose the question back to the EOR - the welded fix is what AISC suggests in their Field Fixes information and seminar.

 

[Teguci]

I think the use of an RFI for this problem is the problem. The cost to make this problem right should be born solely by the plumbing contractor. This cost includes the engineer's time as well as your time and cost of materials to fix this mistake. Request a meeting with the engineer, GC, owner and plumbing contractor to discuss this repair. Don't second guess the EOR, most of us hate that.

 

[dik]

Tequci... they don't second guess me... they ignore me, mostly <G>.

Dik

 

[Forensic74]

EOR get paid for his time correcting field mistakes? Hilarious joke Teguci!!

 

[Teguci]

Its really not about getting paid for the engineering. This is about who is responsible. The time wasted processing the additional work order usually makes this EOR cost inconsequential (ie not worth it). What isn't inconsequential is the additional cost being created when the cores are drilled through the ties wrapping the anchor bolts and the pier has to be removed and recast. As soon as the concrete contractor agrees to the repair he owns implementing it. If the plumber wants to keep his costs down, he needs to get involved (first he needs to own up). And, the best way to keep costs down is to "hire" the engineer to provide a more cost effective solution.

My best suggestion for the concrete contractor (assuming everyone has their ears closed) is to include the costs for replacing the ties that get damaged in the change order and add alternate the less cost for successful cores without damage. This should encourage the start of the proper redesign repair.

 

[hawkaz]

Be careful about coring holes then using epoxy- most epoxy manufacturers require drilled holes, not cored ones. They don't behave the same.

 

[connectegr]

Also note there are maximum tolerances on the size of the oversized holes. I think Hilti RE 500 has the largest tolerance. But this may not be enough to clear the embedded nut and washer.

http://www.FerrellEngineering.com

 

[fancypants]

I have to strongly agree with Teguci. This is not an issue for an RFI. The EOR Should not have to commit more time (unpaid) to a mistake caused by someone else. The contractor that does the work surely will not do it for free. More engineers need to stick to their guns on these kind of issues. Being a team player is one thing but a GC taking bald face advantage is another.


My biggest concern is will this thread be pulled out and used against the EOR?