Designing Lintel to bear on unreinforced masonry 1

[ride5150]

Hi everyone, a friend of mine is taking down a masonry wall and asked if I could design the lintel required to support the 2nd floor-roof brick/floor joists above. I am a structural engineer, but my masonry experience is limited to larger buildings with reinforced CMU...vs single wythe brick home/residential applications.

His contractor wants to pocket one end of the beam parallel to the masonry wall to the "right" in the pictures shown below, and will build a masonry pier on the "left" (against the perpendicular wall). He will place a plate on the masonry pier with studs welded to the bottom and grout. Masonry pier will be reinforced and also tied to the perpendicular wall.

I'm trying to determine the connection on the parallel-pocket side, as well as axial capacity of the wall, as it is completely unreinforced/no horizontal ladders. Can I use msjc methods for "unreinforced walls" even though there isn't horizontal reinforcing? I want him to grout the ~3/4" gap between the two wythes, however I'm not sure how feasible it is to get grout into this small gap.

Connection wise, same plate with welded studs or rebar on the bottom side in one line that would go in the ~3/4" gap, placed when the grout is wet so it bonds.

Pictures:

https://freeimage.host/i/2t3ICG

https://freeimage.host/i/2t3TGf

https://freeimage.host/i/2t3xQs

A couple elevation views/sections describing what I want to do:

https://freeimage.host/i/2D6whP

https://freeimage.host/i/2D6jTB

Can anyone offer feedback? Obviously designing the beam and masonry pier is cake, its the parallel wall and connection that I'm thinking over.

Thanks in advance!

 

[Enhineyero]

Can put up sketch of your proposal, showing existing walls to be demolished and retained, litel location/details, etc. The pictures are helpful but I find it a bit difficult to follow what you are describing above.

 

[ride5150]

Thanks for the response! I freehanded a few drawings and added links to the original post.

The thing I'm most concerned about is the parallel pocket connection to the new lintel, as well as calculating the capacity of this parallel wall as it is completely unreinforced.

 

[hardbutmild]

I wasn't familiar with the msjc methods for "unreinforced walls" until now. I looked it up and as far as I could tell they check the buckling at the mid height of a wall, which should govern, so I'd say that it could be used (but maybe someone more familiar with that code could give you more informations, to me it seems like it should be usable).

I am not sure how this random combination of clay and concrete bricks will behave out-of-plane but if you injection grout it (I think I can see some gaps on photo 3) I think that a safe assumption would be to calculate it as an 8" clay brick wall.

Regarding the connection you proposed, it looks acceptable to me. 10" of bearing length should be enough, but I'm not sure why you'd need the #4 bars welded to the bearing plate (am I missing something? what are those bars supposed to do? I mean, old european masonry buildings have wooden beams just lying directly on the wall and they don't fall out during an earthquake!).

 

[r13]

For the top cap plate, wouldn't a channel be more effective?

 

[ride5150]

Hardbutmild:

Thanks for the feedback. In my day job, our typical detail for WF lintels bearing on masonry is similar to this but with welded studs instead of rebar. Its just for good measure I guess, forms and actual connection between the beam, bearing plate and masonry wall vs just resting on top.

I hope the contractor can somehow injection grout between the wythes, this is my biggest concern.

R13:

A flat plate on top is pretty standard for something like this. I'm assuming your intention with using a channel is to "contain" the masonry wall, channel flanges pointed up.

 

[r13]

ride,

No, legs down. Though I've not checked with number, but I think over all the channel solution will be lighter, but stiffer than plate. Just a suggestion that you might be interested in investigate.

For grout into confined space, it is better to drill/leave a few locations along the wall, and patch up after grout has came out.

 

[Enhineyero]

@Ride5150 - Now I have a good understanding of what you are doing.

I have similar detail as the one you have drawn without the grout and but with a rectangular plate at the bottom portion of the rod embedded at the joints of the brick. This mostly to resist uplift. In addition I have an angle, one leg welded to the bottom flange of the beam and the other bolt fixed to the brick, this is for lateral restraint (i try not to rely on friction).

What is the purpose of the rebar shown in your sketch? is it for uplift? it might not be needed if you are supporting a floor. If its a lateral restraint, this may not be the best solution as you have pointed out that grouting can be an issue.

End lateral restraint for the steel lintel will be best achieved by fixing it from the outside face of the brick via an angle or Channe.

I'm not familiar with American codes for unreinforced masonry but I would definitely check the wall capacity for concentrated load (this is specifically addressed by codes). I have seen these things crack if the embedment is not too long or if load is on the edge (try moving the bearing plate a few inches away from the edge).

Hope this helps

 

[masonrygeek]

Masonry grout injection is pretty common in the restoration world and is used to fill spaces just like this. Of course, it may be best to get a contractor who is familiar with the process as there can be blowouts or other complications. Here is an older article on the subject:

https://www.concreteconstruction.net/how-to/masonry-repair-by-grout-injection_o.

Companies like Edison (

http://www.edisoncoatings.com/Pumpa..._for_structural_masonry_and_concrete_re.html)

and Conproco (

https://conproco.com/product/injection-grout/)

sell products for this process.