Moment of Inertia for Complex Shear Wall Shapes (C / L / etc.)
Moment of Inertia for Complex Shear Wall Shapes (C / L / etc.)
(OP)
I'm trying to use a predominantly shear wall system for a thirteen story post tensioned concrete building. I need to assess the stiffness of the shear walls.
I have concrete shear walls in both C & L plan shapes. In both instances, the "flanges" are about as long as the webs.
It seems to me that, because of shear lag effects, it might not be prudent to consider the entire flange length as being effective. The question then, is how much of the flange should I use?
The other engineers in my office seem to use one of two approaches:
1) Conservatively ignore the contribution of the flanges entirely.
2) Use the entire flange as effective. The idea being that concrete is good at transmitting shear and there will not really be much of a shear lag effect.
Does anybody have any advice that they'd be willing to offer?
Is there any code guidance of any kind available?
Thanks for your help,
Adam
I have concrete shear walls in both C & L plan shapes. In both instances, the "flanges" are about as long as the webs.
It seems to me that, because of shear lag effects, it might not be prudent to consider the entire flange length as being effective. The question then, is how much of the flange should I use?
The other engineers in my office seem to use one of two approaches:
1) Conservatively ignore the contribution of the flanges entirely.
2) Use the entire flange as effective. The idea being that concrete is good at transmitting shear and there will not really be much of a shear lag effect.
Does anybody have any advice that they'd be willing to offer?
Is there any code guidance of any kind available?
Thanks for your help,
Adam






RE: Moment of Inertia for Complex Shear Wall Shapes (C / L / etc.)
RE: Moment of Inertia for Complex Shear Wall Shapes (C / L / etc.)
Yeah, my first instinct was to go with the 6t provision as well. Would that mean that I'd really have to go with 3t then as I've only got flange on one side?
I thought that the 6t provision might be a little too conservative for this application. Here's why:
1) For analysing my PT slab / frame for lateral loads, I get to consider an effective slab width much greater than 6t. So there's some evidence for using greater widths in certain applications. I'm sure that it doesn't hurt that my slab is pre-compressed though either.
2) The shear wall flanges will be well braced at each story which amounts to a bracing spacing of about 9-11 times the thickness of the flange itself. Obviously flange buckling is not much of a concern here.
Any additional thoughts?
Thanks,
AdamP
RE: Moment of Inertia for Complex Shear Wall Shapes (C / L / etc.)
RE: Moment of Inertia for Complex Shear Wall Shapes (C / L / etc.)