Can I treat a concrete shearwall like a perforated shearwall? 1

[reverbz]

Hey Guys,

So I have a concrete shearwall with a significant amount of openings in it. I'm wondering if I can treat it like a perforated shearwall where I only consider the full height segments for shear but get the full length for OT. Would I need special detailing for this(like diagonals at corners of openings)? My thought is we don't because that's more force transfer around openings but concrete is less flexible than wood and I'm not totally sure I can apply the perforated shearwall theory to it. See Image below for an example of one of the walls I'm looking at.

Thank you!

 

[driftLimiter]

The entire wall is going to act against resisting lateral loads. You can decide to treat it the way you proposed but what happens if one of the segments that you did not consider gets overloaded in shear or flexure?

You always want some trim bars around your openings. because there will be a crack there even without lateral loads.

 

[reverbz]

@driftlimiter thanks for the response could you explain "trim" bars? I haven't heard this term. I assume those are the diagonals at corners? And ao you gwnerally consider those enough to transfer the load so those segments aren't overloaded?

 

[driftLimiter]

Trim bars frame the opening and ideally are fully developed beyond the opening vertical, horizontal, and sometimes diagonal are used. The minimum trim bars are called out in typical details of 99% (probably 100% of drawings that I have come across).

Honestly I think you way off mark on this idea. It doesn't behave anything like a wood shear wall and shouldn't be treated as such. But your question indicates that your mind is in the right place trying to address these openings.

This guide on special shear wall design is very very helpful for understanding the concepts needed.

Definitely review boundary zone detailing, and PIERS from that document above.

Also don't lose sight of the out of plane component of strength this wall needs.

 

[hardbutmild]

Also don't lose sight of the out of plane component of strength this wall needs.

In what situation would you consider out of plane strength of the wall? I always assume it to be pinned and transfer the load to the walls in the other directions. It seems more reasonable to dedicate elements that transfer load in each direction separately than to simply assume that everything transfers everything.

Regarding the OP question, I'd suggest using a strut and tie method. It gives you a clear understanding of what is happening in your wall. Every other method in this case (looks like a squat wall) feels like an approximation to me.

 

[driftLimiter]

In what situation would you consider out of plane strength of the wall?

I would consider the out of plane strength in any scenario where the wall needs to resist out of plane loads.

 

[hardbutmild]

I would consider the out of plane strength in any scenario where the wall needs to resist out of plane loads.

What would be an example of that? A free-standing wall? I know you're trying to make fun of my question, but in regular cases there are walls in both directions.
It's not an outer basement wall because of the holes.
The only realistic scenario that even comes to mind is outer wall exposed to wind action. This is usually so small that other things govern.

For example if you have a 20 cm thick wall minimum reinforcement (according to eurocode, but it's probably similar) is 2 cm2/m on each face, usually 2.57 cm2/m is put (a standard mesh of 8mm bars at 15 cm spacing), which leads to 19 kNm capacity. If you assume a simply supported beam of 5 m height (very large storey height) you'd get that capacity is reached at 6 kN/m2. This is extremely high for any wind action that I ever saw.
This is why I asked what would be a practical scenario where minimum reinforcement would not be enough for out of plane.
I am genuinely interested since nothing comes to mind.

 

[EZBuilding]

Out-of-Plane components and cladding wind pressures, would cause out-of-plane shear and flexural behaviors into the wall.

 

[driftLimiter]

I wasn't making fun of your question. perhaps I was a bit blunt.

Wind loads perpendicular to the wall. seismic load of the wall itself.

Piers that are adjacent to openings steel can easily be governed by out of plane behavior for slender walls with significant out of plane forces.