Brick Deflection Limits
Brick Deflection Limits
(OP)
I am aware of the commonly accepted limits of 0.30" or L/600 for brick lintels, whichever is less.
For very long spans the 0.30 requirement can be unreasonable. For example, a 40 ft. span truss that deflects 0.50 inches (L/960) has less angular rotation than a 15 ft. beam that deflects 0.30 inches (L/600). In my opinion, the angular rotation is the issue, not the absolute deflection.
Is there any relief to the 0.30" requirement for very long spans?
For very long spans the 0.30 requirement can be unreasonable. For example, a 40 ft. span truss that deflects 0.50 inches (L/960) has less angular rotation than a 15 ft. beam that deflects 0.30 inches (L/600). In my opinion, the angular rotation is the issue, not the absolute deflection.
Is there any relief to the 0.30" requirement for very long spans?






RE: Brick Deflection Limits
RE: Brick Deflection Limits
Australian code has not total deflection limit but limits deflection to L/500 for articulated brickwork (joints ar 18' or less) and L/1000 if not jointed.
.3" at L/600 is equivalent to about 15' so similar to the aticulated brickwork span in the Australian code.
This agrees with haynewp's comment suggesting jointing the brickwork.
RE: Brick Deflection Limits
Does L/600 deflection also apply to veneer brick, such as walls made of 1 whythe brick with cold formed metal framing and wall board?
RE: Brick Deflection Limits
RE: Brick Deflection Limits
RE: Brick Deflection Limits
I would say yes; the wall doesn't know if it is a veneer or load bearing in this context.
RE: Brick Deflection Limits
RE: Brick Deflection Limits
"The curvature of the support should be limited to L/600 but it can exceed 0.30" if control joints are provided at 15 ft. o.c."
With control joints at 15 ft., if the supporting beam is limited to L/600, the deflection of the independent brick panels between control joints would be (15)(12)/600=0.30. The independent brick panels will not know that the overall deflection of the beam is more than 0.30.
RE: Brick Deflection Limits
I wouldn't though.
Brick is a "real" load. That 40 psf is there all day long, all week long, all year long, and usually masonry buildings arn't the type that get ripped down in 25 years.
I've used L/600 for 30' spans on spandrel buildings before (pre-IBC), and that 0.6" of deflection is noticable.
And what do you say in 30 years when you come back and 20% of the section is corroded away?
Anyways, I'm a proponent of building with brick conservatively, use the 0.3" maximum as a tool to educate architects, owners, and contractors that it really does make sense to limit masonry deflections.
RE: Brick Deflection Limits
The masons will have difficulty if the beam deflection is too much! As they build the wall they can increase the masonry joints slightly. Keep in mind a masonry joint is 3/8" and they want to build those joints level. As the beam deflects, they try to widen the joints to keep the top course level. As the lower courses cure, they add to the overall stiffness. Intermediate control joints will prevent the masonry from arching.
RE: Brick Deflection Limits
RE: Brick Deflection Limits
If it does not arch it will not crack!
The deflection when they are building the wall, before a lot of the load is added and before long term deflection, will be very small if the total long term deflection is going to be .3 or .4".
We can come up with lots of arguements like this.
RE: Brick Deflection Limits
RE: Brick Deflection Limits
RE: Brick Deflection Limits
Are you saying that you use a flange width for the beam equal to the span length of the beam? Your deflections would always work according to this. Too bad it is not what really happens.
Why don't you use the code defined flange width which tries to estimate the width of flange that will actually contribute. It is maximum 25% of the span length but related to slab depth as well.
RE: Brick Deflection Limits
RE: Brick Deflection Limits
RE: Brick Deflection Limits
DaveAtkins