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Masonry Wall Sub Panels - Lateral Analysis

psychedomination

Structural
Jan 21, 2016
123
Hi there,

I’m working on a masonry residential project that has quite a few window and door openings. I’m trying to wrap my head around how to break the wall up into separate panels.

The British standard gives the following example :

IMG_0390.jpeg

However, I don’t fully understand the 2nd option. Why don’t those two top squares show any load distribution? Wouldn’t there be a line load from the window on their free edge? Wouldn’t they also be taking a wind load, therefore distributing that load to top, bottom and right? Or is the assumption that the whole top portion is an opening?

Is there any videos, text or books you can recommend that give more examples of this, where walls are broken in to sub panels due to openings?

For my specific scenario, my walls and openings are as follows:

IMG_0391.jpeg

The project is using concrete masonry units. Wall panels will be hollow, the reinforced bands will be filled with concrete and reinforced as required. I know that adding sill reinforcement may simplify the panel analysis between the windows but it’s not really typical to put in sill reinforcement where I live, so I’m checking if it works without. Ideally, I’d like to minimize the strong bands if they aren’t needed.

In the British standards, it appears that it allows you to increase the panel overall UDL if a line load is present on a wall panel free edge.

I’d appreciate your thoughts. Is there a more efficient way to layout the strong bands and sub panels? Is what is proposed reasonable? Note lateral wind loads are quite high ~2.5 kPa. Vertical bands will be sized to take the wind loads to the diaphragm.
 
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Is this an upper and lower story? i.e. is there a floor system near mid-height?
 
@XR250 What’s shown is the ground floor. There is a basement level underneath but that is not shown in the sketch. There is no floor system mid height for the ground floor level. Strong bands are reinforced masonry in the wall.

The wall height is ~14’6” tall with 10” concrete masonry units.
 
@XR250 ,what do you mean by demand?

There are no floors above this ground floor level, so I'm conservatively neglecting any positive contribution from deadload. The roof system (diaphragm) will be a flat reinforced concrete slab roof. The floor system will also be a reinforced concrete slab. Both slabs 6" thick.

Lateral load consideration is only wind load that has an approximate UDL design pressure of 2.5kPa.
 
1. No matter how you “cut” the wall, equilibrium must be satisfied.
2. Shear is zero at free edges.
3. The more and larger openings you have, the more the wall behaves as a frame and can be approximated with a suitable portal frame analysis.
4. NEHRP No. 9 has some modeling guidance in Section 4.
5. 2012 DORMS provides an approach to the load distribution in Section 3.8.4.
6. Pay close attention to boundary conditions and corners of openings where masonry is likely to crack.
8. Reinforce per internal stress, acknowledging that load will concentrate in stiffer parts of the wall.
9. Software example Here
 

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