Internal brick wall - lateral restraint at top 7

[LR11]

I've been trying to find out if there's a requirement to restrain internal brick walls which act as a shear wall.
This would be at the top, to the roof or roof truss members.
This would be a common scenario to any dwelling with internal brick walls.

At the moment I have a gap in between ceiling and top of wall (see image).

 

[BAretired]

It is not clear how the interior walls can act as shear walls if not connected to the roof or ceiling to resist a horizontal force parallel to the wall. A cornice on each side could be adequate to resist lateral force normal to the wall, but that doesn't make it a shear wall.

BA

 

[LR11]

Thanks for responding.
Is it not like this:
WIND ON ROOF TRUSS: Using trimmers, see example below.
WIND ON EXTERNAL WALLS: Two leafs/wythes in two way bending, load on external leaf to internal leaf via cavity ties ... internal leaf then bears on the perpendicular internal wall. For any suction pressures, cavity ties between internal leaf and internal perpendicular wall.

Is that not how it works.

 

[Aesur]

@LR11 I'm not sure you are understanding what we are trying to say regarding transfer of lateral loads to a shear wall that isn't connected at the roof. See below for a quick example/explanation of what we are saying. Hopefully this helps you better understand, please ask any questions you may have.

 

[LR11]

Aesur, are you sure about this?
I thought that external walls are able to go into flexure, supported on 3 sides (bottom and 2 vertical sides). As is the case for the internal leaf/wythe. The external leaf has the internal leaf as backing, the term I've seen mentioned.

Also the detail that you have, I've never seen angles inside a dwelling.

 

[EcoGen]

I thought that external walls are able to go into flexure, supported on 3 sides (bottom and 2 vertical sides). As is the case for the internal leaf/wythe. The external leaf has the internal leaf as backing, the term I've seen mentioned.

I truly mean no disrespect, but I think you need to educate yourself more on how lateral loads, shear walls, and diaphragms work together. Shear walls are designed for in-plane horizontal forces (load parallel to the wall) at the top of each wall section. We don't depend on them for any resistance for forces perpendicular to the wall (i.e. flexural out of plane bending).

That's because they are too flexible in out-of-plane bending versus in-plane shear. So before they even start bending due to perpendicular forces, other shear walls parallel to those forces have already picked them up. We could try explaining here with diagrams but you need to read up on this more yourself.

 

[Settingsun]

He's saying that his shear wall supports another (exterior) wall that's at right angles to the shear wall. The shear load is a distributed load along one vertical end of the wall, not at the top of the wall.

 

[dik]

For residential construction, I wouldn't normally use an interior partition for lateral resistance... there's another issue about truss uplift...

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

-Dik

 

[EcoGen]

He's saying that his shear wall supports another (exterior) wall that's at right angles to the shear wall. The shear load is a distributed load along one vertical end of the wall, not at the top of the wall.

I have always thought the load path is: wind on exterior wall > half of wind trib distributed vertically to top of wall > top of wall to diaphragm > diaphragm to shear wall. Just like Aesur has shown in his diagram above.

The way you described it, the load path would have to be: wind on exterior wall > horizontal distribution (instead of vertical) of wind trib > to adjacent connected shear walls. In other words, shear walls act like supports for the exterior wall.

Unless you specifically design your exterior wall to transfer forces horizontally, I don't think the horizontal distribution of the wall would ever occur.

 

[r13]

What is the length of the interior shear wall? Doesn't it have transverse support along its entire length?

 

[Aesur]

I agree with @manaf_engineering; while technically possible to distribute the load from the exterior wall to the interior wall through bearing against the end of the interior wall, I highly doubt a 2 wythe brick wall would transfer more than 3 or 4' of tributary area. You would need to design the exterior wall to span horizontally from support to support as if it were a floor bearing on two walls; we would need to know project dimensions to even begin to start looking at if this is remotely feasible, but I suspect it's not based on what I have read thus far.

@LR11, can you provide a basic sketch with dimensions of wall locations and lengths, this will go a long ways toward helping us to help you?

 

[LR11]

No disrespect manaf but you need to read my responses as well. I have not said the shear wall's purpose is to take an out of plane load, the issue is the lateral resistance required (2.5% or similar) in order to brace it laterally. Having said that, I believe there may be a nominal requirement for out of plane loading, 5psf was mentioned previously, and I believe our code may use 0.5kPa which is about 10psf.

Your point about the load arriving at the shear wall ... regardless whether via to the diaphragm at the top or by bearing into the internal wall, the exterior walls have to go into bending.
I do take the point about having to check this though, not having restraint on all 4 sides.

r13, the length of the internal wall/s may be anywhere between 3m to 4.5m, the dimensions of the dwelling are typical. The support at the top: the cornice will to brace laterally for the 2.5% nominal load, the trimmers to connect the truss chords bottom chord to the interior walls.

Aesur, I can tell your trying to be helpful. I will look into the capacity of the wall to see if I need to restrain at the top. The dimensions are for a typical dwelling, say up to 4m or 5m rooms, about 15ft, and ceilings are 3m or 10ft. One of the issues is that it's a reverse brick veneer construction and depending on the builder, the truss may land on either leaf/wythe or both. For that reason I'm assuming no lateral restraint at the top.

 

[r13]

If your room size is 4m - 5m, then wouldn't be the shear wall is laterally supported by two transverse walls spaced 4m - 5m apart? It should help you in lateral stability concerns.

 

[LR11]

r13, sorry but I don't understand what you mean.
Just on the off chance I have used term "shear wall" incorrectly, it's the internal yellow coloured walls in the image below.
I'm reasonable comfortable now about the stability, by this I'm inferring you mean the nominal 2.5% lateral restraint required.

 

[r13]

LR11,

Each of your interior wall is supported on two edges, which greatly improves lateral stability.

 

[LR11]

OK, thank you that does make sense. It gives me an extra degree of comfort.

 

[r13]

Sometimes we look at a component and forget it is in a structural system, so look both may help.

 

[BAretired]

Walls A and E are on the exterior, so I assume they are double wythe brick walls. Presumably, they are tied into the floor system, so they should be okay as shear walls.

Walls B, C and D are single wythe brick walls, tied on each end and on ground floor level. I believe they would be adequate to serve as shear walls for some of the wind force delivered by the exterior walls spanning horizontally. If the exterior walls cannot span the full distance between brick shear walls, the other partitions may be used as well.

Any partitions, whether brick or stud and drywall, which are intended to resist wind pressure must be tied into the exterior walls to resist both positive and negative pressure.

BA

 

[LR11]

OK thanks to both.