Shear wall fixity
Shear wall fixity
(OP)
I am hoping someone can clear this up for me...
Let's say there is a 2-story building with a concrete-filled diaphragm 2nd floor and metal deck roof. Shear walls span from floor-to-floor and are connected to the underside of the steel floor/roof beams. Are the shear walls designed as fixed piers on both floors or are the shear walls spanning from the second floor to the roof considered cantilevered since the roof diaphragm is flexible? Also, is reinforcing sized based on overturning of the entire system (if the walls are vertically in the same plane from floor to floor-i.e. no vertical/plan offsets). I wouldn't think so, and the reinforcing is only sized for the moment in a fixed pier at each floor. Thanks.
Let's say there is a 2-story building with a concrete-filled diaphragm 2nd floor and metal deck roof. Shear walls span from floor-to-floor and are connected to the underside of the steel floor/roof beams. Are the shear walls designed as fixed piers on both floors or are the shear walls spanning from the second floor to the roof considered cantilevered since the roof diaphragm is flexible? Also, is reinforcing sized based on overturning of the entire system (if the walls are vertically in the same plane from floor to floor-i.e. no vertical/plan offsets). I wouldn't think so, and the reinforcing is only sized for the moment in a fixed pier at each floor. Thanks.






RE: Shear wall fixity
Your question indicates that you need to start a thorough study of lateral load paths. There are many books on the subject. Breyer's wood book comes to mind immediately.
DBD
RE: Shear wall fixity
On the other hand, I must respectfully disagree with Dr. Taly and say that I have always considered shear walls to be cantilevered on each level. I do not see how the lower stories can be considered to be fixed-fixed, since this analysis assumes that the top of the shear wall can develop a moment to resist the lateral load. If it can, then to what does it transmit the resisting moment? It could only transmit it to the story above, and that only leads up to the top of the building and a dead end.
Regarding your question about reinforcing, I usually consider each pier on each floor individually, with the shear wall at the top story designed as a cantilever with only a point load at its end, and all shear walls below designed for a point load (story shear) and a point moment (the moment developed at the base of the shear wall immediately above to resist overturning) at their ends. I hope this is of some use.
JS
RE: Shear wall fixity
RE: Shear wall fixity
RE: Shear wall fixity