Brick Veneer Angle Lintel Design - Limited Veneer Height Above 1

[marinaman]

I have a brick veneer lintel, in design, that is caught up in a grey area:

My angle needs to span 10'. It supports 40 psf brick veneer. The angle size requested by the architect is a 7" x 4" x 3/8" angle.

The brick above the angle is only 5'-4" tall.

All this being said, I'm trying to determine if the 7 x 4 x 3/8 angle is ok.

If more masonry was above the angle, I could assume triangulation of the veneer (arching action) and the use of tables that I have would be fine, but in this case, I don't think there's enough veneer above the angle, so I think the angle must be designed for the uniform load of the veneer.

As best I can tell, in the BIA Tech Note, it looks like, if the veneer is laterally tied to the building via brick ties (which it is), then the angle can be designed to the allowable stress of 22ksi. If that's the case:

Span = 10'
Veneer Ht = 5'-4"
Load = 213 lb/ft
Moment = 32,000 lb - in
Section Modulus Needed = 32,000/22,000 = 1.45
Section Modulus Provided = 4.42 of a 7" x 4" x 3/8" angle
Deflection = 0.0817 (L/1467)
Bearing Stress = 44 psi

To me, the 7 x 4 x 3/8 looks fine.....but I'm wondering about the allowable stress that BIA recommends, at the 22,000 psi. Seems like it should be less.

Can anybody provide me guidance as to a design guide for angles that have limited veneer above them? There's no other loads.

Thanks guys,

MarinaMan

 

[SteelPE]

Why not check the angle per AISC section F10 requirements?

 

[phamENG]

I agree with SteelPE. Check it using AISC and calculate your deflection thoroughly (you're going to have vertical and horizontal deflection even though you're only loading in the vertical). Be sure to consider how the architect is orienting the angle in their details. A lot of the 7" angles I see are LLH to close the gap between the veneer and the wall and make flashing easier. With the veneer that far out, and at 10' of unbraced length, the twist will be enough to add appreciably to the total deflection of the angle under the veneer.

And be careful with assuming arching action - if the mason is fast enough, they'll load it up before the mortar sets up enough to prevent movement. If you're not designing for full UDL, it may be worth telling the mason to shore the lintel, especially for longer spans.

 

[r13]

The allowable bending stress is correct, for A36 steel, fb = 0.6Fy = 21.6 ksi. However, the design could be controlled by compression. For L7x4x3/8, r_y = 1.12, KL/r = 120/1.12 = 107. The corresponding fa = 12.07 ksi (A36), and 13.04 ksi (A50). You should check the maximum compressive stress due to bending.

For long leg up, r_x = 2.27, KL/r = 120/2.27 = 53. The corresponding fa = 18.08 ksi (A36), and 23.88 ksi (A50).

 

[XR250]

If this is residential, just use the building code. I believe you are allowed to use L5x3 1/2x 1/4 up to 10 ft.
I typically use L7x4x3/8 for 10 ft. spans and never check it. Honestly, if you actually check twist deflection they never seem to work out.

 

[masonrygeek]

Take a look at BIA Tech Note 28 on brick veneer on wood stud walls - it contains a table on lintel size which is taken from the IRC:

https://www.gobrick.com/docs/defaul...28-brick-veneer-wood-stud-walls.pdf?sfvrsn=0.