Steel lintel
Steel lintel
(OP)
I came across a design problem that I am not sure if I have enough information to solve. I have a 6x6 steel angle supporting 500 plf of brick. Deflection is limited to L/600. What is the minimum thickness of the angle? I am not sure how to go about this when the span of the lintel is unknown.






RE: Steel lintel
Yes I agree, I suppose you could select a length like say 10 metres or whatever and workout the thickness then pro-rata it if and when you do now the length.
Why haven't you got the length whats the reason for that?
desertfox
RE: Steel lintel
RE: Steel lintel
In that case I wonder whether you solve it for a minimum length of 1ft, then I would check the answer if you have it in the book.
desertfox
RE: Steel lintel
RE: Steel lintel
RE: Steel lintel
Even working a deflection for a beam only a foot long probably won't be very accurate because the length to depth ratio for beam formula is to small.
Anyway mike any chance you can upload the question and/or give the answer in the book?
desertfox
RE: Steel lintel
RE: Steel lintel
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Steel lintel
Since you have a weight of the brick veneer of 500 plf, that indicates a significant height of veneer above the opening, which indicates arch action is very possible. The arch action dramatically reduces and almost eliminates the deflection.
You are right that it all depends on the opening width, which does affect the load in the lintel, but if you have enough height over the lintel, the arch action will reduce the load on the lintel dramatically and the Romans recognized this principal very quickly.
Dick
RE: Steel lintel
RE: Steel lintel
Patrick
RE: Steel lintel
Since the compressive strength of the veneer is not a problem, it usually is a mute point.
Pay attention to any shelf angles and soft horizontal joints that will disrupt the arching action and then you have a simple vertical load bearing situation with none of the benefits or arching. Depending on the properties of the veneer (clay brick expands with time) and concrete masonry and concrete have some long term shrinkage/creep. Woof frame has serious shrinkage and stability issues and usually will have a horizontal shelf angle at 16'or so. I have seen 7 story buildings without a shelf angle and the top floor windows suffered because of the 2" different vertical movement between the vertical expansion of the brick and the relative stability of a concrete frame.
Since you have a 6x6 angle, you probably have a true masonry veneer with an air space or insulation between the veneer and the structural back-up. Wall ties provide the horizontal resistance/alighnment to transfer horizontal loads to the structure
Dick
RE: Steel lintel
RE: Steel lintel
From paddingtongreen's post of 16DEC, 10:57 and down, there is much good, real world info. on lintel design, once you know the span length. But, read and digest druminman's post before you apply this real world info.
RE: Steel lintel
RE: Steel lintel
The vertical control joint also destroys the arch effect since the horizontal thrust cannot be recognized.
I agree since I neglected the vertical control joints that negate the advantages of the arch action that the ancient Romans did not have to deal with for permanent construction in total masonry construction with is historically proven for the total structural performance.
Dick
RE: Steel lintel
In middle of the opening - possible
On sides beyond bearing areas - possible
On edges of the opening - not possible
The OP question wasn't a trick, it was seriously flawed. Where was that question came from?
RE: Steel lintel
RE: Steel lintel
The "possibility" has no practical value.
RE: Steel lintel
Arching not only hates joints, it also requires adequate masonry width on either side of the opening to take the lateral thrust of the brick.
And I agree that the question the OP references is BS.
RE: Steel lintel
Even with joints at both sides, arching can be considered, if needed, because all of the load above the arch comes down as two, almost point loads adjacent to the supports. Having said that, I have to agree that if I cannot control the location of the joints, I use the uniform load.
I've been retired for a while, but I mainly used precast lintels or bond beams in the later work years.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Steel lintel
I agree with your post since there is more to the structure than just the veneer. This was not posted as having a classic arch, but only a typical veneer on a structural back-up installed within the construction restraints and few details.
Since there is no information on the rest of the structure, the arch action may not be used because of detail restraints (horizontal or vertical joints), the use of the lintel to support the veneer is the only design resort or alternative.
It sounds like a probing classroom question with not enough information to give an intelligent answer, but they may grade on opinions and the "curve".
Dick
RE: Steel lintel
The arch will act the same, whether it's a built classic arch, or an arch formed by the dropping away of the brick triangle above the lintel.
RE: Steel lintel
RE: Steel lintel
With the help of some falsework, you can model this with children's wooden blocks and dry joints.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Steel lintel
I think what you are getting at is that there is a component of friction between the brick and the steel angle that takes this horizontal thrust and thus the weight can all come down as concentrated right at the ends of the angles. I don't like to count on friction for structural stability.
RE: Steel lintel
I'm nerdy enough that I did the experiment with wooden blocks when I was young and learning the business. I admit that I did nothing to lessen the friction though.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Steel lintel
I have seen pictures and field examples of what JAE talks about. Obviously, a real arch over the opening, in a brick veneer, will have more horiz. thrust reaction than the opening with a structural lintel under the brick. The lintel is their, at least, to carry the triangle of brick that Michael says falls away (an unreliable function, in tension, of bond btwn. brick and mortar), when the false work is removed. I agree with JAE re: friction at the steel lintel, but that's called bond btwn. the bricks as we talk about the corbel.
RE: Steel lintel
I wouldn't rely on it for desigh though, unless a positive stop is fixed to the lintel.
RE: Steel lintel
BA
RE: Steel lintel
Dick
RE: Steel lintel
RE: Steel lintel
The only possible criteria is availability so the answer must be 5/16" since that is the smallest size available.
RE: Steel lintel
Anyway, forget all these digressions about "arching", and how the supported load may or may not behave--they've TOLD you the load is exerted in a simple linear distribution across the lintel span. That's why I mentioned catenary. Pull out those undergrad texts on beam deflection.
Plug and chug. Enter a L-ength, solve for thickness. IIRC you'd need modulus of elasticity, and possibly other INtrinsic properties of the steel, plus EXtrinsic (handbook) properties of the angle stock.
Academic perhaps, but it seems like a good P.E. exam question, as it gets to FUNDAMENTALS, and knowledge thereof. Work-a-day solutions gleaned from handbooks lead us away from the analytic principles of how the values were arrived at. (Hopefully there's a large empirical component as well.)
I'm pretty sure in the real world there is not a continuous range of angle stock thicknesses, e.g. every 5 mils, so after you plug n' chug your MIN thickness, you'd select the next largest size, yes/no?
Anyway, what do I know?... I'm a Comp Sci/Math guy who used patching concrete to repair/reinforce/seal the severely rusted mild steel C-channel beams holding up his propane BBQ grill, LOL! (Working out great, BTW.)