Use out-of-plane capacity of wall to resist lateral load?

[RyanTa]

This is a 6 storey building. The walls (200mm thick) run in x directions only. Due to the architectural layout, no shear walls can be arranged in y direction, I might add some internal columns between walls for gravity supports. All floors are flat slab.
My question is, can we reply the out-of-plane capacity of wall to resist the lateral loads? I have never done it this way but cannot explain why it will not work. If we simplify this structure as frame, make the wall(out-of-plane) to slab as rigid connection then it will give you the capacity to resist lateral loads. I have checked the strength of the walls and it is okay. The deflection is also under limit. So it there any other considerations that I miss?

 

[BridgeSmith]

If I'm not mistaken, in most, if not all taller buildings, the shear resistance is provided by internal shear cores, formed around stairwells and elevator shafts. Even with open stairs, there are innovative and aesthetically pleasing ways to integrate shear bracing into the stair support structure. Some beefy cross bracing would also not look out of place in even a glass elevator shaft.



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[r13]

Doesn't your building code requires two egress?

 

[Tomfh]

And as the connection between these two blocks are weak and I would treat them as separate diaphragms.

If they’re connected they’re connected. You happy for the remaining link to simply tear?

 

[bones206]

RyanTa can you post a plan view showing the full layout with the core locations?

 

[RyanTa]

Here is the markup of the floor plan above first floor.

 

[bones206]

Are you planning to have the diaphragms connected throughout the left, right and middle blocks? Or are you planning to have expansion/seismic joints and separate lateral systems for each block?

 

[RyanTa]

I am currently just working out the preliminary. I tend to treat them as separate diaphragms using joints (although here in Australia no much consideration is given to earthquake and I don't think it is popular here to use seismic joints). Even if they work as a one diaphragm, the structure will be horrible under earthquake considering the torsion caused by the core location. So it gives me a headache.

 

[hokie66]

You didn't answer retired13's question. Where is the other point of egress, thus the other core?

Also, what are the overall dimensions of the proposed structure?

 

[bones206]

Even if they work as a one diaphragm, the structure will be horrible under earthquake considering the torsion caused by the core location.

Probably a challenge even under wind load, given the transverse lateral stiffness is so concentrated at the core walls way off to the right AND the diaphragm has two big notches in it. It’s hard to see this working without additional transverse shear walls on the left somewhere.

 

[Lomarandil]

Hokie -- 14m was mentioned earlier, so I'd guess the left side is about 14x14m and the right side maybe 10x14m.

Yeah, I think you're definitely right to treat these as separate diaphragms (assuming that you don't end up with a second core stiffening the left side).

----
just call me Lo.

 

[phamENG]

If you have to split them and use a seismic isolation joint - yikes. In a building that tall the joint would be huge, wouldn't it? I had to put a 6" joint in a 1 story steel building once - can't imagine a 6 story building (even if it is concrete).

At the end of the day, physics is physics and without a proper load path the building will come down no matter how artfully designed the facade is. The walls are probably going to be too slender (unless you make them 24" thick) to do what you want them to do out of plane. The architect can still get their pretty all glass curtain wall - but you should insist on columns set in along the length and design traditional moment frames to go with them.

 

[JLNJ]

Use moment frames where you say "internal wall might add columns here".

 

[r13]

As the plan shown, you simply don't have much luxury to successfully design the building as a whole, it just has too many irregularities (lacking end walls, the necking and the offset stair/elevator core). I suggest to perform a preliminary analysis, summarize the weakness/problems, then sit down with the architect to work out a better layout/solutions.

 

[rowingengineer]

Would you consider a moment frame? I think there was mention of gravity columns couldn't these be used at the lateral system as well?

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