Adhesive Anchorage (ACI 318) 2

[BadgerPE]

On a current project, I specified Simpson AT-XP acrylic adhesive be used to anchor large silos to the concrete foundation. This product is approved for installation down to 14 degrees Fahrenheit. However, where we are, temperatures are already below this for extended periods so the contractor has requested to use Simpson AT acrylic which is approved down to 0 degrees Fahrenheit. This is where my question arises.

The AT-XP (originally specified) meets strength design provisions of ACI318 Appendix D. However, the AT (requested substitute) does not as it is only has ASD design methods listed. If the AT adhesive has sufficient capacity to anchor the silos to the base under service loading, would it be an approved substitute? Or should it automatically be rejected due to it not meeting strength design provisions?

 

[msquared48]

Call Simpson.

Mike McCann, PE, SE (WA)

 

[TehMightyEngineer]

Yeah, the manufacturers of the epoxy anchor systems bend over backwards to help us engineers out (makes sense, we spec it and they sell more, they want it to be easy to design with).

Maine EIT, Civil/Structural.

 

[JAE]

Yes - it appears that the AT adhesive doesn't meet ACI 355.4 which is a requirement of Appendix D.

So you either see whether ACI Appendix D (i.e. ACI 318) applies to your project or not -

OR

You heat the area involved to get it above the thermal limit for AT-XP.



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[jayrod12]

Or go to a different manufacturer. Perhaps Hilti Hit-ice adhesive. base material temps down to -10F

 

[BadgerPE]

Thanks for the info all! I have a call in to Simpson so I will see what they say.

JAE,

When you say "See whether ACI App. D applies to your project" were you thinking something specific may apply that would get me away from ACI App D? Perhaps that these are silos and non-building structures? I would like to get a real solid handle on this situation as it looks like we will have several more silo projects crossing our desks in 2015.

 

[JAE]

Sometimes projects are located within jurisdictions where perhaps the building code is unique and refers to something other than a late edition of ACI 318.

Also - sometimes projects, as you say, are not within a jurisdiction, or there is no building authority reviewing the design as is typical of silos, rural areas, etc.



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[BadgerPE]

Upon speaking with a field engineer for Simpson (incredibly helpful by the way) I learned a few things about the AT-XP adhesive. First, it is not approved by AC308 for cracked concrete and thereby ACI 355.4 as JAE alluded to. However, it may be approved for uncracked concrete under AC308 and he is checking on it. Second, the 14F threshold is based upon testing in accordance with AC308 and to the best of his knowledge, no adhesive anchor that meets the requirements of AC308 has been successfully approved for use with a base material below 14F. I am going to do a little research to see if Hilti makes any that are approved below 14F though for peace of mind.

Learned some interesting stuff today and made a valuable contact for future use. Thanks again for the help!