bent anchor bolts
bent anchor bolts
(OP)
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!
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!






RE: bent anchor bolts
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
RE: bent anchor bolts
http://www.FerrellEngineering.com
RE: bent anchor bolts
RE: bent anchor bolts
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
RE: bent anchor bolts
http://www.FerrellEngineering.com
RE: bent anchor bolts
Dik
RE: bent anchor bolts
RE: bent anchor bolts
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.
RE: bent anchor bolts
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.
RE: bent anchor bolts
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...
RE: bent anchor bolts
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
RE: bent anchor bolts
RE: bent anchor bolts
RE: bent anchor bolts
Dik
RE: bent anchor bolts
RE: bent anchor bolts
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.
RE: bent anchor bolts
RE: bent anchor bolts
http://www.FerrellEngineering.com
RE: bent anchor bolts
My biggest concern is will this thread be pulled out and used against the EOR?
RE: bent anchor bolts
It would also be prudent for the GC to protect the anchor bolts from construction traffick which may bend the bolts.
BA
RE: bent anchor bolts
I think the moral of the thread here for all of you engineers is be careful what you suggest. In this case certain persons in the project want to proceed even though they know problems can arise from the procedure. It is unfortunate that it is construction101, always cover your a$$ and be ready to be able to blame someone else. My company and myself usually try to take the high road and look out for the project as a whole, as you could see I could have easily passed the buck on this one. If i didn't take the high road i could potentially be pouring slabs on deck in winter conditions!! see why it pays to take the high road.
And while I often read a lot of contractor bashing here, there are some contractors that care about their work and are truly professionals. They are experienced, and with an equally talented engineer, can deliver a great product.
Connectegr-you are correct re500 is allowed for cored holes while hy150 is not...had to bring that to everyone's attention too, otherwise hy150 would be installed according to procedure.
I did suggest they explore the options listed in design guide 1 and let me know if they will represent this to the engineer.
RE: bent anchor bolts
RE: bent anchor bolts
RE: bent anchor bolts
Dik
RE: bent anchor bolts
http://www.FerrellEngineering.com
RE: bent anchor bolts
http://www.FerrellEngineering.com
RE: bent anchor bolts
Most contractors that deal with anchor bolts have needed to weld extensions or make repairs. Therefore a WPS should be included in their QC paperwork.
http://www.FerrellEngineering.com
RE: bent anchor bolts
RE: bent anchor bolts
Dik