Headed Stud CMU wall spacing 2

[trussme91]

Hello everyone,

I have been following this website for a while now and I finally became a member. I want to start off by saying hello to everyone out there. There really is a great depth of knowledge here. Now, down to my question...

I am working on anchoring headed studs (5/8 in. diam.) into a CMU wall. I am not too sure where to look for applicable spacing requirements, as I already looked through ACI 530. I read 20db in an ESR report but that's for concrete and I found somewhere else that says 1"+db but that's for decks. Please let me know your thoughts.

Thanks

 

[hokie66]

Not clear to me how headed studs and CMU walls work together. Maybe you can furnish a sketch?

 

[sandman21]

They are used in the back of embed plates in lieu of bolting plates to the face. You will determine the capacity based on ACI 530 with overlapping cones for the anchors. Closely spaced anchor will have more overlapping area and thus a smaller increase in load. What are you trying to design?

 

[dik]

8" o/c seems pretty good unless continuous, then maybe 16" o/c. Used to use a continuous strap with studs to secure metal deck at outside walls of buildings...

Dik

 

[hokie66]

I still don't know how these are to be built into a CMU wall. Are they in the face or the top?

 

[dik]

Hokie: You set them into the grout, or, pour the grout around them... usually use 1/4" or 3/8" anchors except for bearing plates...

Dik

 

[sandman21]

A couple different configurations, mostly used as beam supports; face shells and webs are removed and the plate is set flush with the face of the wall, the mason then grouts around the plate. We use them for beam supports and we weld reinforcing to the plate as well. Never used anything less than 3/4"Ø or with a bearing plate.

 

[trussme91]

Sandman21- The design is for a stair stringer channel resting & welded to an angle that is then anchored into the face of a CMU wall. I designed this connection per ACI 530. The governing shear failure was masonry shear crushing. I can not however find the critical spacing between anchors. I have come up with (4) 3/4" diam OR (5) 5/8" diam nelson studs embedded 6".

Dik - Where are you getting the 8" or 16" o.c.? ACI 530?

 

[dik]

OP: Just to fit the core locations in the CMU's

Dik

 

[KootK]

I'm not sure that there really is a minimum spacing requirement. Just as with concrete anchorage design, as your anchors get closer together, the failure cones will overlap and effectiveness will be reduces. Kind of self penalizing. This is an excellent document pertaining to the design of these things in the US. There's even a link in there to a handy spreadsheet that can be used once you've come to terms with the underlying concepts.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[trussme91]

KootK- Thanks for the share. I already did research that pdf, but was wondering if I was missing something with the anchor spacing. I'm going to go with 8" o.c. and leave say a 6" bolt to angle edge distance. Usually for concrete ESR/LARR reports are pretty thorough in terms of anchorage spacings, etc. so I thought masonry would be the same. At least for studs it seems to be slightly different. Thanks again guys.

 

[KootK]

Usually for concrete ESR/LARR reports are pretty thorough in terms of anchorage spacings

Are there min spacing limits for studs in concrete anchorage situations? That's news to me. I thought that the only limit was good sense as there's little point to having multiple studs once their failure cones become practically concurrent.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[sandman21]

Stud rails have spacing requirements, possible they reviewed that or the stud lists ACI 318 requirements for spacing, 4d not torqued or 6d torqued..

 

[KootK]

the stud lists ACI 318 requirements for spacing, 4d not torqued or 6d torqued..

I'd like to check this out. Can you direct me to it any more specifically sandman?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[sandman21]

ACI 318-14 17.7; ACI 318-11 D.8