Lintel size for 12' 3" arched opening

[gjanardh]

We have a arched opening of 12' 3" with a single story above (see link below for front elevation). I am trying to understand the lintel size needed. Could you please help me interpret this code for lintel size and span table available at

http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_7_par058.htm

The last line in the table says we need 2 Nos of 6 x 3 x 5/16 lintels. Is my understanding correct?

Lintel Ordered -

Thanks for your inputs.

 

[thaidavid40]

Your limiting worst limiting-case for bending would be for a straight beam, with no arching action to help. I imagine that if you reinforced for this condition, that you would be okay. Remember though to check the lateral thrust reactions at each end to make sure you have sufficient capacity there to resist that. Keep it simple, and that goes for the analysis too.
Dave

Thaidavid

 

[WARose]

That table appears to be for normal beams......this is a curved/arched beam. Under certain geometries, a curved beam will develop higher stresses than (straight) beam flexural formulas will predict.

I'd call a local a structural engineer. Not only will he need to make the calcs on the beam but will also have to decide what the load on the lintel actually is. (I.e. is the masonry above suitable to provide arching action. That is: is the geometry right? Are there any joints in that zone? Can the adjacent masonry take the thrust of the reactions?, Etc.)

 

[XR250]

You might consider putting a straight beam behind it up high that bears on the wood framing (assuming wood backup). You could attach the high point of the arch to it to break up the span. Yea, it ain't ideal due to wood shrinkage etc., but it seems to work OK on large span garage doors.

 

[HouseBoy]

I like the curved lintel approach and have used it many times.
My question for OP is : HOW MUCH DID ONE OF THOSE LINTELS COST?
I did one recently and it was about $1500 (I think) for a single angle spanning about 9 feet and maybe a 6x4x5/16 angle. I don't know if that is common price range or not and am curious what others are finding.

ALSO : Those look painted but - do you recommend Hot Dip Galvanized or some special paint spec? Just wondering since rusted steel lintels are a common condition (although not usually a problem with brick wont opening until they are about 30 or 40 years old). Thing is, commercial code requires HDG but I really don't see it done all the time.

For WARose : What geometries are you referring to (for higher stresses in arched than straight?

Thanks

 

[gjanardh]

Thanks for your inputs everyone.
I did not buy these arched lintels, it was bought by the builder. These are 2/8" in thickness and I am trying to understand if its a proper size for load above.

 

[WARose]

For WARose : What geometries are you referring to (for higher stresses in arched than straight?

In general, I remember the difference becoming larger as the height of the arch became greater. To be on the safe side, I always run the curved beam formulas (no matter how shallow the arch is). Also remember that the buckling for an arch is different than straight beams.

 

[hokie66]

Those curved angles on the ground...what are the leg dimensions, vertical and horizontal?

For such a shallow arch with relative narrow bits of masonry at the jambs, I would just consider it a beam.

If the lintels are for permanent use in the wall, they should be hot dipped galvanized.

 

[HouseBoy]

I would guess that arching action could be "rationalized" (mostly) as the 12' span isn't too great and there is plenty of brick above and a reasonable amount of brick on the ends to resist the thrust (might be a bit high though).

Looks like the horizontal leg is about 8" wide and the vertical leg is upright on the back side of the arch and less than 8". I think that whole arrangement is unusual and I would expect the eccentric loading (greater loading on the "outside" half of the angle is not a good thing). I have not done the analysis but I would expect the whole thing to be problematic unless arching action is at work. Single angle design is a PITA and this one has added wrinkles.

Still with all that said, undersized steel singles on single family residents is one of the most common things I see on houses and it seems that it almost never rises to the level of a concern (due to adverse behavior) although I really wonder sometimes why it does not. In other words, many undersized lines are installed and they ought to fail but they just don't seem to fail often enough of anyone to recognize how "close to the line" they really are.

That's my 2 cents anyway.

 

[gjanardh]

Thanks for your inputs everyone. I appreciate you all. I have sent some requests to the builder based on your inputs.

 

[XR250]

many undersized lines are installed and they ought to fail but they just don't seem to fail often enough of anyone to recognize how "close to the line" they really are.

I think it comes down to the fact that the masonry ends up acting like a deep beam. It may also get enough bond with the lintel so it may be acting as a partial tension flange.
I talked with a tech. rep from the brick institute at one point and he recommended adding joint reinforcement in the first couple of brick courses above the lintel to do just that. I don't know how effective that is due to the laps etc., but it likely would do something.

 

[HouseBoy]

XR - I'm not buying any of that.