Expansion anchor + epoxy anchor 4

[slickdeals]

Folks,
Is there any restriction anywhere in the code that prevents the use of an expansion anchor in conjuction with a epoxy anchor?

Can a load of 50 kips be carried say 20K by expansion anchor and 30K by epoxy anchor?

Any reference to portions of literature or code is appreciated.

Thanks

 

[Lion06]

I don't know of a restriction, but why would you do this?

 

[slickdeals]

I have a situation where a new steel column is being attached to the soffit of an existing beam. I am trying to use expansion anchors to attach the cap (base) plate to the soffit because I am not comfortable with the overhead installation of epoxy. I am then coming up with a detail to attach the column to side of the beam. The column is in essence a 50' long beam carrying wind loads.

 

[msquared48]

I would be very leary of using an expansion anchor anywhere near the edge of the beam due to possible spalling of the concrete, whether you use epoxy or not in conjunction with the same expansion anchor.

Mike McCann
McCann Engineering

 

[271828]

If you're using a cap plate, won't your column accept vertical loads also?

 

[slickdeals]

The cap plate is going to be attached to the soffit. The steel column will get a double angle connection from the cap plate to the column. No bearing.

 

[slickdeals]

In retrospect, I should not have called it a cap plate.

 

[271828]

No problem.

I don't quite understand the detail. Why not just use all adhesive anchors? If you'd trust them to take a big chunk of the load, might as well trust them to take all of it. (I think that makes sense, LOL).

 

[UcfSE]

You should check how these anchors deflect with load before you combine them. That will determine how they share the load. You may find one carries more than the other, and it may not be the one you want.

 

[271828]

UcfSE, that's a good point, IMO.

If we're talking about ductile limit states (may or may not be--not sure what's controlling), then perhaps they both can develop their ultimate strengths in the end even if they have unequal stiffness for lower loads.

 

[registeredpe]

Greetings,
My first response to your question would be, is this a tensile, shear or oblique loading condition? or is this a combination of all of the above as it makes quite a difference? secondly, where is this expansion or epoxied anchor located on the existing concrete? thirdly, what is the compressive strength of the existing concrete? refer to the allowable (i.c.c./i.c.b.o) approved tension,shear and/or oblique loads as per the manufacturer as well as the edge, end and spacing distances as provided by the manufacturer. Most of all I am quite concerned that this load of 50 kips (whether it be shear, tension,oblique or a combination thereof) is way beyond the allowable loads found in the Simpson or Hilti catalogs. Additionally, I highly recommend that you consult with a registered professional engineer in the state that you reside in for additional information.

Thanks for listening(reading), P.E. in Arizona, USA

 

[lkjh345]

slickdeals:

Just my 2 cents worth, but have you considered Large Diamter Tapcons (RedHead) or Titen HD (Simpson)? Another product out there that some has some positive (in our eyes) characteristics versus expansion anchors.

Full Disclosure: We are currently unclear of the status of ICBO approvals for these products for use in cracked concrete (per ACI Appendix D). Appearently, their previous ICBO approvals expired Jan 1st.

 

[registeredpe]

Greetings once again:

I just realized that I did not refer to the allowable bolt loads. Go to

http://www.simpsonanchors.com

 

[PEinVA]

registeredpe,
Your comment about 50kips being greater than the allowable loads on the epoxy/expansion bolts says everything it needs to about your cocky invasive attitude. It is clear no one is questioning that he is going to use a single bolt to create his connection, which you seem to assume and want to use this as your justification to be this demi-god of engineering. This forum is meant to expand knowledge and no one on this site ever claims to know everything or really answer questions. We guide people around and just have discussions.

It opens up 100's of more colleagues than just the 4 or 5 most of us work with. It's a great tool, but tools are only as good as the craftsmen using them. Read some of the policies on the board and some other threads.

Thanks.



RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[KCRatnayake]

Agree with UcfSE.

Displacements under loadings vary with different anchors. When it's come to adhesive and mechanical expansion anchors, this is more significant. Due to this, some anchors can be over loaded and failure can occur. In a worst case this failure can be like a chain. I heard some engineers call this failure phenomina a "Zip Fastener Effect".

Clefcon

 

[BPA827]

If you're installing an expansion type anchor to the underside of a concrete beam (which is what I understand is what you're suggesting, you need to consider if the beam is in tension on the bottom face at the loction you want to install. If so, this will undermind the anchor connection, as the concrete expands in tension and will loosen the anchorage

 

[slickdeals]

The anchor is being installed into the soffit at the end of a cantilevered beam. It is a prestressed soffit beam.

 

[KCRatnayake]

If it's installed in soffit of the end of a cantilever, that is your anchor is not in the tensile region of the concrete. Some anchors don't have approval for setting in tensile regions.

Anchor type to be used depends on magnitude of loading, edge distance, base material thickness, anchor specing etc.

If your beam is narrow and loading is high, I would probably go for adhesive anchors or under-cut anchors. And I would not use different type of anchors in one group.

KC

 

[registeredpe]

registeredpe,

Greetings again, I agree with clefcon's post.

Another thing to bear in mind is that the cantilevered concrete beam may not have tensile steel in the compression side(bottom)of the beam and by introducing a new support at the end of this cantilevered beam, a stress reversal will take place making the bottom of the beam subject to tensile loading which may have catostrophic results.

Thanks again, registeredpe in AZ

 

[Lion06]

registeredPE-
He said in an earlier post that he is providing a double angle connection which will provide for no bearing of the concrete beam at the cantilevered end. I am presuming he is just using slotted holes in the double angle connection with a gap between the beam and the post.
No need to worry about stress reversal.