Steel angle lintel - composite action requirements 5

[LR11]

I have a single leaf brick wall over a garage opening, approximately 6m wide.
I want to support using a steel angle of size 150mm x 100mm (or 6" x 4").
I've heard about composite action but do not know how to convince myself it's achieved.
The angles are plain and galvanised (I have hard about ribbed angles which are known to offer composite action but these are not available in my area).

With the composite action, I'm guessing the strength requirements will easily be achieved. For deflection, I intend to prop at one or more locations until mortar is set, thereafter I'm guessing it will be more than OK. Torsional effects, will no longer be relevant.

Has anyone handled this in the past?
Have you come across any documentation or testing which will provide confidence with a plain un-modified length?

 

[GeorgeTheCivilEngineer]

There are a few research papers from 1950s-1970s but no design guidance that I have seen. It isn't a clear cut model as there is arching action in the masonry and the composite action is via friction only.

I... wouldn't rely on it for strength or deflection. But it is reassuring knowing that steel-masonry composite action is likely to reduce deflection even further.

 

[dik]

I would not likely use an angle for a 20' span...

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) Interesting, I've never heard this argument made seriously before. Engineering dogma does tend to be different in different parts of the world though.

2) One of my major concerns with this is that the twist in the angle under load will tend to break the composite bond upon which one hopes to rely. Granted, this effect will be lessened a the ends of the member where the demand for shear transfer is at a maximum.

3) This strikes me as a bit of a catch 22. The way to retain bond between the materials is probably to make the angle stiff enough to limit movement. But, once you've done that, you probably no longer need the composite action.

 

[r13]

For masonry wall in double wyes construction, you can weld studs, or metal strips on the angle to make it acting compositely with the brick. But, I don't know any reference.

 

[phamENG]

I wouldn't depend on composite action without some sort of positive attachment between the masonry and the lintel - hard to achieve with solid brick.

I read an article a few years ago - probably in Structure - about design of masonry veneer as masonry beams. The essence is that horizontal joint reinforcement is placed between courses to take the tension, and you rely on the masonry above to do the compression work. Pretty straightforward and an interesting approach. The lintel is essentially shoring, or you just use a temporary lintel.

Would I ever use this approach? Probably not. Where I practice, veneer construction quality is not great, and they always use the cheapest mortar they can get their hands on with no QA system for testing its strength or measuring the mix proportions. So attempting a real design would be a bit of a WAG. Try to get a mason accustomed to doing veneer to do something with inspections and special materials is just asking for a problem.

 

[LR11]

Thanks for all the responses.
My argument came from a reference which sounds similar to the one phamENG mentions. Experimental tests were carried out.

Now that's out of the way, what would you do for this case then?
- Using an inverted tee is unsightly on one side, and prone to twist.
- A central universal (joist) beam is also unsightly in my opinion.
- A hollow section? I try to avoid because I have seen them corrode internally despite welding caps at the ends. Pouring a mix internally, to limit corrosion ... I know there will be complaints.

 

[phamENG]

Single leaf brick - same thing as a single wythe brick wall here. I'm assuming, then, that this is a veneer. What is the structural wall system? and what is supporting the opening? I'd tie them together somehow. The how will depend on what it is.

 

[Tomfh]

I’ve never really trusted the composite action. There are these notched ones which supposedly provide better composite action:

https://www.galintel.com.au/wp-content/uploads/Galintel-Product-Guide-2019.pdf

 

[LR11]

phamENG, you've got me thinking now.
The overall construction is termed Reverse Brick Veneer. I'm not familiar with it.
The drawing shows a single leaf for the garage, and I have assumed it's brick. Up until now, I haven't been able to find useful details on Reverse Brick Veneer construction. I have assumed the brick is the load bearing side, but I could be wrong.
Perhaps I need to confirm this first. Embarrassing, sorry if it's wasted people's time.

Tomfh, it's interesting to hear your opinion on the composite action for the ribbed sections.

 

[dik]

Even if wood stud wall... adjustable masonry ties would be suitable to keep it from falling forward.

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

-Dik

 

[LR11]

@dik, the ties would be for the double leaf construction, right?
For the single leaf at the garage, that was one of the items I had to look into at some stage.

 

[GeorgeTheCivilEngineer]

A channel section lintel or steel could work. Less inclined to twist and cut bricks can be placed in the web of the beam.

In the UK IG lintels have this:

https://iglintels.com/product/l11/

and you might be able to find a channel that performs the same job.

 

[phamENG]

If this random blog that I found is reliable, looks like a standard stud and veneer wall turned inside out: Link

In that case, It almost doesn't matter what you use as it's going to be hidden inside the wall and the bricks may not be visible. And if they are, it's in a garage. Assuming you can get over the thermal bridging that would occur, you could just put in a wide flange shape to carry the whole thing. You may need to at that span.

 

[dik]

They can be used for multi-wythe (leaf) construction (or header courses)... but, they can be used for stud wall backup or for CFS construction. Whatever you need to maintain stability of the construction. Ties have to be vertically adjustable.

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

-Dik

 

[LR11]

OK thanks for the additional comments.

 

[Settingsun]

What were the conditions where you saw sealed hollow sections corrode?

 

[LR11]

steveh49, there have been two instances observed first hand. On a minesite where a trafficable steel hollow section grillage was used for tipper trucks. Secondly for communication towers, with hollow section columns, particularly at the base.
I understand the environment is not as severe, however I want to be careful given that it is residential.