Design of Angles 4

[dik]

A bit of an article...

https://www.newsteelconstruction.com/wp/wp-content/uploads/2022/07/NSCJuly2022Tech.pdf

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[canwesteng]

How much twist in the angle can you see if the vertical face is up against the masonry? I would question how the angle even buckles torsionally in that arrangement, either the vertical leg must push through the masonry, or the horizontal leg must lift up the masonry. Seems impossible as long as local bending capacity is sufficient.

 

[dik]

I usually take the eccentricity of the load to be near the back of the angle, and not at the middle of the masonry. I've even seen the 1/3 point used, with the 1/3 being to the front... everyone uses a different location, it would seem... my approach is less conservative, but I've been using it for 50 years without issue.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[human909]

How much twist in the angle can you see if the vertical face is up against the masonry? I would question how the angle even buckles torsionally in that arrangement, either the vertical leg must push through the masonry, or the horizontal leg must lift up the masonry. Seems impossible as long as local bending capacity is sufficient.

I'd ask the converse question. How much torsion can the bottom of an suspended masonry wall resist? Is this torsion resistance greater than the torsional load applied to the masonry wall by the angle in bending?

 

[JLNJ]

As the angle tries to rotate, the bearing point of the brick moves away from the centerline toward the inside face of the brick. This does cause some flexure in the brick, but so be it.

And I agree with the question regarding the torsion. You can't just put a tube member in there "because tubes are good in torsion" unless you have torsional fixity into the supports at the end of the member.

 

[canwesteng]

I guess the other thing is I've always sandwiched the CMU with angles on both sides, so there is no torsion in the brick. I'd probably steer away from details imparting torsion into the brick except for very light loads. The double angles should be cheaper and easier to install than the HSS system, assuming it is properly detailed to resist torsion on its ends.

 

[dik]

I have no idea why that was done, I would not want to try to develop torsional rigidity at the end bearing conditions.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[masonrygeek]

Here is an old thread on the same subject:

https://www.eng-tips.com/viewthread.cfm?qid=34243.

See also BIA's Tech Note 31B where they talk about torsion on p.4:

https://www.gobrick.com/docs/defaul...es/31b-structural-steel-lintels.pdf?sfvrsn=0.

 

[dik]

Thanks, mg...

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Celt83]

@masonrygeek:
Tech 31B doesn't present much info on resolution of the torsion seems to just kick out to AISC for the angle provisions.

As an aside:
Table 1 in Tech 31B shows 2-1/2" horizontal legs for lintel use wouldn't these violate the 2/3 bearing requirement for the veneer?
Can you provide any resources for the dimensions of bond beams and lintel blocks, the NCMA Tek notes don't list the interior dimensions at all and seemingly a lot of block suppliers don't have that info either?

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)