Loose Lintel End Reaction Bearing in Stacked-Bond Masonry

[MJC6125]

For brick veneer in stack bond, is there any reason I should be concerned with using a loose lintel schedule at face value as it relates the end bearing of the loose lintels?

I understand that the brick above an opening can't corbel in stack bond, so I have to design the lintel for all the weight of the masonry above. However, I'm wondering if I should be taking any precautions due to the fact that the end reaction of the loose lintel also will not corbel into the rest of the veneer wall?

See the image below as an example. If I had an 8" wide brick column on one side of an opening and had running bond masonry veneer, I would think twice about whether that loose lintel is a good idea or not. That's basically what you have at every opening in stack bond.

I assume we are good because the brick bearing length is checked based on the compressive capacity of the brick, and the brick shouldn't buckle or fail due to combined bending & axial like a column because it is tied back to the structural wall continuously?

 

[masonrygeek]

for any stack bond brick veneer there is a requirement for a minimum of horizontal joint reinforcement to help tie the brick wythe together (Section 12.2.2.10 of the TMS 402-16). In the code they call stack bond, "veneer not laid in running bond". This is usually a single wire W1.7 spaced no more than 18" o.c. Since brickwork often bonds out at 16", the joint reinforcement is placed in that joint. This reinforcement will help you with load distribution above and below the opening, but you have designed this correctly.

 

[JedClampett]

Check the attached. It's from 1987, so you know it's good. It doesn't address the affect of the stack bond on your bearing capacity, but I think bearing is a local effect, so it probably wouldn't.
Can you make the ends into reinforced brick columns?

 

[JLNJ]

I would not count on the bearing on the right side of your sketch being distributed out quite so generously as you show it, running bond or not.

 

[ProgrammingPE]

A concentrated load next to an open cannot spread out in the 1:2 ratio that you would use in the middle of wall. Also, for stacked bond you can only spread the load out through bond beams or up until you reach a head joint.

Structural Engineering Software:

http://www.structuralcentral.com

Structural Engineering Videos:

http://www.youtube.com/channel/UCOj2mXXf3ZbZtgxTc6BtkGg

 

[MJC6125]

Interesting. Do you think the bearing reaction spreads out to the remainder of the wall at all on the right side or no based on that bottom right figure from ProgrammingPE's post (Assuming we had running bond masonry)? If it doesn't spread out much at all then the fact that the steel lintel is bearing on stack bond instead of running bond masonry, shouldn't matter?

I am just dealing with brick veneer on a residential project in my case, so I wasn't thinking reinforced brick columns were going to be necessary.

 

[BAretired]

With brick veneer, the load should be small, but for a lintel, I don't believe the load spreads out very much, if at all.

BA

 

[dhengr]

MJC6125:
There was a masonry wall reinforcing unit called a double wire ladder, a std. ladder reinforcing unit with two extra longitudinal wires, spaced apart, and welded to the cross wires down the center of the std. unit. I’d cut the cross wires just outside the two extra longitudinal wires, so I ended up with just the two extra wires tied together. I would cut these to lengths to bridge two, three ad four bricks, and you don’t want the cross wires at any of the head joints. I would put these in three or four bed joints immediately below the lintel bearing bed joint. This will tie the brick ad brick courses together in some fashion, and cause some corbeling out into the wall, although it’s probably not covered by any code section. And, I would double or triple the number of brick ties back to the structure in this area of wall, along the jambs. Alternatively, you could take a std. W1.7 wire 5 or 6’ long and bend it at its center, around a .75” or 1” pin and use that in the 3,4, or 5 bed joints below the lintel brg., then every 5 or 6 bed joints down the jamb. I think I’d want to see some bed joint reinforcing at the same vert. spacing on the whole wall. That’s the price the Arch. pays for his want for stacked bond. I believe the IBC and the IRC do allow these lose lintels for brick veneer, but only for self-weight, not other large concentrated loads, and with a bunch of limitations and footnotes. There isn’t much doubt that the brick has the compressive strength for some lintel bearing loads (how much?, your engineering judgement). The weak link is the lack of stiffness (kl/r), as a column section, of the veneer brick at the jambs, and its buckling potential. And, then the general lack of attention to detail and poor masonry construction, particularly on residential work. This area of the construction certainly calls for some special inspection and observation, at the start of the brick work, to get them off on the right foot, ad to show you mean business. Residential work is notorious for poor detailing, specing. and installation of brick ties for brick veneer work. Nobody worries about that until the veneer start falling of the bldg., ad there are almost no ties or they are rusted off.

 

[masonrygeek]

For additional information on this subject, go to the Masonry Institute of Michigan's website and scroll down to Design: Stack Bond -

https://www.masonryinfo.org/faqs/.

Remember that you are looking at brick veneer and not a loadbearing block wall when reading the provisions.