Lintel or no Lintel? 2

[XR250]

The builder does not want to use a lintel. I wouldn't either. The window is 6 ft. wide with 4 ft. of wing wall on each side. How do you all feel about a few courses of joint reinforcement over the arch and call it a day?

 

[jayrod12]

Isn't the arch blocks a lintel on it's own? Or are you concerned that you're lacking the walls on either side to buttress the thrust?

Full load bearing masonry? Or is there a back-up wall?

 

[XR250]

Brick veneer over 2x6's. Yes, the lack or buttressing is my concern. Does not seem like much of an issue in this case.

 

[RWW0002]

Attached is a BIA Tech Note on arches that I have found useful in quantifying arch action and thrust resistance.

 

[jayrod12]

If you're specifying more robust ties than the galvanized 22ga garbage, then I'd likely be ok with it because you could engage the 2x6 wall sheathing a bit. Something like a fero tie.

 

[MIStructE_IRE]

Depends how good the bricklayer is!

 

[dik]

You have lots of masonry on either side...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[KootK]

1) I second dik's sentiment that it looks as though you've got a fair bit of thrust resistance to work with.

2) Given that it's a gable end condition, you're probably not dealing with much more than the self weight of the wall for gravity load.

2) I like the reinforcement as belt and suspenders. If you do get any spreading tendency, the reinforcement would kick in fast and the load on the lintel could be as little as the triangle of brick above it.

 

[dik]

KootK: Because the arch is high, the horizontal thrust is minimised. Digressing, about 45 years back I did a building with a masonry bearing wall in it and a mandoor... as constructed the Italian mason (not a racist, but some of the best masons I've encountered are Italian) constructed a circular arch with a 20' span... The workmanship was beautiful. It took me days to analyze that...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[XR250]

Ran some quick numbers and it looks like I should be fine w/o reinf. Will add it anyway in the first two courses above the opening.
Thanks for everyone's insights.

 

[hardbutmild]

Easily stands under vertical loads if the thickness is more than 1/10 of the radius (so around 4 inches if my calculations are correct).
If you could fit a catenary inside it then it's safe. Usually, you can fit two catenaries (one that gives you minimum and one that gives you a maximum thrust.

Maximum thrust is
H = w*l² / (8*h)

H = thrust
l = clear span + 2*thickness of the arch
h = radius to intrados
w = distributed load on top
See the pic.

Under the thrust calculate the piers next to the window. Check that principal tension stress is below 0,1 MPa.
See pic under.

I believe that overturning can't really happen (as well as sliding along the horizontal plane, but you could check those as well.

 

[masonrygeek]

Loadbearing masonry arches were so much easier when we had multi-wythe walls. Veneer arches are still doable, especially for short spans, but not everyone knows how to design them. Semi-circular arches often can be used without a steel angle, but as the rise of the span decreases, there is more horizontal thrust to deal with and more of a chance of a crack occurring midspan as noted by hbm requiring a steel angle. Besides the BIA TN 31A on arches (which is tad dated), they have another publication that is more appropriate for residential arches:

https://www.gobrick.com/docs/defaul...efs/brick-brief-arches-may-2012.pdf?sfvrsn=0.