Lintel - Supporting 12" Masonry
Lintel - Supporting 12" Masonry
(OP)
I have a school with a fine arts building. It has an opening for the stage of 45’, and I need to design the lintel. The CMU above is a 44ft and I feel I can not do triangle loading due to the need of control joints. Also, it is supporting a fly-loft and roof, because I can not do the triangle loading (DL = 4000plf, LL = 1200plf).
I have tried fixing column to help with deflection, but for a lintel of this length I am having very heavy members.
Is there any suggestions on a better approach for this long of a span?
I have tried fixing column to help with deflection, but for a lintel of this length I am having very heavy members.
Is there any suggestions on a better approach for this long of a span?






RE: Lintel - Supporting 12" Masonry
Is there depth for a steel truss? Perhaps you could design a reinforced CMU beam?
RE: Lintel - Supporting 12" Masonry
Regards,
YS
B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...
RE: Lintel - Supporting 12" Masonry
I assume you are in the interior, where you lose some of the factors creating the normal requirements, which usually are used for both interior and exterior applications in the interest of simplicity.
You would still have the curing and carcbonation shrinkage of the masonry units (at least 75% occurs before laying) and the mortar shrinkage. You may be able to eliminate the moisture shrinkage and the effects of temperature, which can be major items for an exterior wall, but may not exist for your specific situation.
RE: Lintel - Supporting 12" Masonry
I have plenty of room to develope what I need, and was indeed looking to do the truss. However, in general, we try to keep a 3/8" deflection on masonry, but for this long of a span I thing 3/4" to 1" should be adequate. I have been informed that as deflection occurs during loading masons adjust there grout spacing.
Thanks for everyones input.
RE: Lintel - Supporting 12" Masonry
If you have jointed masonry then the larger deflections will not be a problem as long as your joint widths are sufficient to take it.
The 3/8" limit is more for when you have arching and the masonry above a certain level will stay where it is and the masonry below this will deflect with the lintel. A crack would then develop at the interface between the 2. In the arching case the actual deflection is important and is not related to the span.
In your case, if you use jointed masonry, then all the wall will move as one. It is then the rotation of the panels and the curvature of the beam that is important. Both of these are related to span.
RE: Lintel - Supporting 12" Masonry
RE: Lintel - Supporting 12" Masonry
I work for an A&E firm, we don't design them with the fly loft anymore. I guess there have been advances in rigging that have (thankfully) allowed us to get away from the fly loft.
RE: Lintel - Supporting 12" Masonry
Dik
RE: Lintel - Supporting 12" Masonry
RE: Lintel - Supporting 12" Masonry
DaveAtkins
RE: Lintel - Supporting 12" Masonry
I worked on three high school auditoriums in Brevard County, Flordia many years ago. These big beams spanned the stage and looked AWESOME.
RE: Lintel - Supporting 12" Masonry
I designed one of these almost exactly as Gordy2 describes. To maintain the CMU look from inside the auditorium we supported a 4" veneer on the bottom chord. It seems to have satisfied the architect. It hasn't been built yet, though.
RE: Lintel - Supporting 12" Masonry
Article 1.10.1 deflection limits don't apply to reinforced masonry designed according to section 2.3.
RE: Lintel - Supporting 12" Masonry
I just design all my lintels and beams to L/600, or 0.3" max, and figure I'm covered.
RE: Lintel - Supporting 12" Masonry
I don't see these as contradictory. Article 2.3.3.4.5 says that beams must meet 1.10.1. Article 1.10.1 says to limit deflections when the beam is supporting unreinforced masonry.
So, if a beam designed to 2.3 is supporting a wall designed to 2.2, it must meet the deflection requirements of 1.10.1.
If a beam designed to 2.3 is supporting a wall designed to 2.3, it does not need to meet the deflection requirements of 1.10.1.
Many engineers meet those requirements anyway (see previous threads on this topic), but I don't believe it is required by the code.
RE: Lintel - Supporting 12" Masonry
RE: Lintel - Supporting 12" Masonry
Recently we finished school project, which started w/ exactly same problem. We proposed to use metal stud wall over proscenium, which is much lighter, and not required such killing deflection restriction and brick veneer just for exposed portion of wall, above roof over audience seats. By our proposal, veneer should be supported by DLH joist.
Architect accepted our proposal without any further discussion.