Design of RC Cores

[asixth]

What is everyone's approach to RC cores. I normally build up the core in RAPT and design for Axial Load and Bending. I change the tension controlled and compression controlled reduction factors down to 0.4 and 0.3 except when I provide compression ties to the vertical reo, then I keep the factors at 0.8 and 0.6.

Regards

 

[rowingengineer]

Depends on the height of building and if I am including coupling walls, but I see nothing wrong with your approach.

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"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[Trenno]

What effective length do you input into the column module of RAPT?

 

[asixth]

I don't. The whole assessment on whether a wall panel is slender or not is something that I assess as I go along. Generally it's not critical but it does become critical at some thin door jambs between openings. At those locations I assess the slenderness on a case by case basis. Or if there is a large void adjacent to the core where the restraint is lost.

The reason I ask is that I see people ripping wall forces out of etabs and assess each panel one by one. I have no issue with doing that I'm just a little concerned by the coarseness of the FE meshing. You pull forces out but don't get the smoothed design stress interaction. Like with a ram concept floor model, you don't design for the peak spike in slab moment over a column but distribute it over some slab strip width.

 

[Trenno]

So is this the cross section module in Rapt? Mine always says that it isn't supported in my version or something...

What you're getting at is people should be using an M / Z approach for the whole core as opposed to isolating each panel?

 

[asixth]

Yeah, just seeing people to wrapped up in etabs output. I think the need to be mindful of the real behaviour. Particularly with fe modeling where the meshing can be a little coarse. And the code does talk about group of walls so I think the group should be considered. This approach has happened at a few places I'be been but I prefer to look at the core as a whole.

 

[rapt]

Trenno,

It would be the Column module that produces M/P interaction diagrams.

 

[Trenno]

Interesting, I'll have to give your method a whirl sometime.

Obviously this relates to RC in-situ cores, I can foresee some issues arise when you start using precast panels stitched together as cores.

 

[asixth]

Oh yeah, I wouldn't even attempt to stitch together precast walls to use as a core for a lateral resisting element.

 

[bowlingdanish]

That's interesting - we do that all the time asixth. As long as you provide plates that can transmit the longitudinal shear in the walls and dowels that can fully develop I don't see the issue. Mind you I still hate precast concrete.