SHear flow

[slickdeals]

Folks,
This maybe a stupid question, but there is something about it that I don't understand entirely. In the attached sketch, I am having a hard time figuring out how the shear from the diaphragm finds its way to the back wall (running east-west). Your thoughts and views are appreciated. Thanks

http://files.engineering.com/getfil...df6c-4f36-9706-a8b3a27cb754&file=File0174.pdf

 

[JAE]

Through bending in the twin parallel walls....only way I see.

 

[whyun]

Thru the bending of the bond beam on the cross walls and the bond beam reaction ends up on the end wall and the open side of the diaphragm.

Make sure the beam connecting to the bond beam is "anchored" properly.

 

[271828]

Yep, definitely only through out-of-plane bending of the two walls running plan N-S. A dubious load path, IMO.

 

[msquared48]

Does not look like a very good shear wall to me. I would look at other options. Even in the transverse direction, the walls are relatively short and will need drag struts to get the shear force to them. Could complicate the floor and roof framing.

Mike McCann
McCann Engineering

 

[DaveAtkins]

I don't think the diaphragm shear CAN get to the shear wall.

DaveAtkins

 

[haynewp]

Depending on the amount of shear to be transferred you might can design the 2 walls as short cantilevered concrete beams. But you will have to develop the end moment into what you are calling the shear wall and the beams will have to be able to take the shear also. The wall would then have the shear plus an edge moment applied at each end of the wall = In-plane shear + torsion along the wall's vertical axis.

Locally you have to get the diaphragm force into the back wall through bending but the entire shaft could function as a composite C shape with torsion and shear if designed and constructed this way. It looks like an interesting problem which may be possible depending on the level of force you are dealing with and the thickness of you walls. I would think twice if it is a medium to high seismic area, I think it would function as somewhat of an in-plane moment frame that would need special detailing attention.

 

[slickdeals]

Thanks guys, this is not a real shear wall on any job I am working, but I have seen other drawings where wall of similar nature are present and I could not trace a load path in my head. In a computer program, it will see shear , but how would anyone detail it ?

 

[msquared48]

Wow! You are slick, aren't you. And we thought we were dealing with a real problem here. Now we're all depressed...

Mike McCann
McCann Engineering

 

[271828]

It will resist very different amounts of shear depending on whether the computer program is using a rigid (or membrane) diaphragm or is using shells to model the deck and walls. In the latter, more accurate, case, it might not resist much shear depending on the rest of the lateral system.

The only way to use this situation, IMO, is to accurately model the walls (i.e. not a membrane or rigid diaphragm) and then design the walls to have enough out-of-plane flexural and shear strength. It would be better to come up with another arrangement.