Welding anchor rods to baseplates

By msc Date 02-14-2006 16:42

I'm currently involved in a machine foundation repair that will involve post-set epoxy-type anchors. It has been mentioned from the contractor who will be performing the repair that the anchor rods be welded to the plate, as opposed to bolting (for reasons such as corrosion, clean-up, maintenance, etc.). I haven't heard back from the manufacturer of the epoxy in regard to the possibility of destroying the epoxy bond to the concrete following welding. Has anyone had any experience with welding post-set anchors to baseplates, or should I avoid this type of attachment all together? (1" diameter anchors and 1" thick plate)

By jon20013 (*****)

Date 02-14-2006 19:26

When I read your question, it brings me back to several issues we faced during construction of power plants. My interpretation may be off base but I will ask you some questions:

1). What if the machine needed to be moved at some future date for whatever the reason might be?

2). Is there any reason that the machine would require a given amount of torque or tension to the foundation? If so, how would this be verified? In other words, assuming the anchor bolts were set satisfactorily, how would you ever know if somehow they loosened?

3). I guess, in my personal opinion, this sounds like a bad idea for a number of reasons, including those questions above but one more thing to consider; the anchors are likely of some hardened material, what would the metallurgical effect of welding have on the physical properties of those anchors?

By msc Date 02-14-2006 21:22

Thanks for the response jon20013. To answer your questions and to give you a little more background to the situation:

1). The entire machine is anchored to the foundation by welding the machine pedestals to steel plates and W-shapes that were embedded in the original concrete foundation. It is our goal to permanently fix the machine to the concrete foundation (moving the machine to another location is not an issue).

2). We are dealing with a Baler/Logger/Shear machine that is being used by a recycling outfit. The machine manufacturer will not provide any information as far as the dynamics of the machine go, except that they recommend that the anchoring system be designed to resist upward forces equal to the dead load of the machine at it's attached point plus an additional 50% for live load and impact. It is believed that this type of impact loading caused to original failure between the plate embed and the anchors that were attached to it. And due to the dynamics of the machine as its operating, we will know immediately if the anchors have failed or loosened.

3). We have considered some of the same effects that you have mentioned. However, due to the uncertainty of the actual loadings that the machine is producing during operation, we have included additional safety factors and a bit of an overkill as far as the size of materials that have been selected. I guess we were more concerned about the effect of welding on the bond between the epoxy/anchor/concrete rather than any metallurgical effect of welding on the physical properties of the bolt. The manufacturer of the epoxy recommends the use of an all-thread rebar (Grade 75 - ASTM A615) for use in conjuction with the two-part epoxy system. What are your thoughts in regard to welding this type of anchor to a baseplate.