Maximum slenderness koef. for sway frame
Maximum slenderness koef. for sway frame
(OP)
Hi!
Usualy we use monogram for determing value of K,wich will be multiplied with columns lenght. l=k x lo.
For non-sway frames maximum teoretical value is k=1,00, but for sway frame its k=infinite!
Anyway I found that people are always talking about k,max=2 for sway frames. Even so, this value would be applied only to a column thats fully restraind at the bottom and compleatly free at the top, wich clearly, in a typical frame constuction is never a case, because you always have columns that are conected to beams/slabs!
So my question is wich would be a maximum vaule of K for sway frames?
Usualy we use monogram for determing value of K,wich will be multiplied with columns lenght. l=k x lo.
For non-sway frames maximum teoretical value is k=1,00, but for sway frame its k=infinite!
Anyway I found that people are always talking about k,max=2 for sway frames. Even so, this value would be applied only to a column thats fully restraind at the bottom and compleatly free at the top, wich clearly, in a typical frame constuction is never a case, because you always have columns that are conected to beams/slabs!
So my question is wich would be a maximum vaule of K for sway frames?






RE: Maximum slenderness koef. for sway frame
That beind said, many people don't design sway (moment) frames with fixed bases. That is typically a last resort to keep column sizes under control or to control drift. Therefore, theoreticaly, the bases re pinned and the intermediate stories are restrained by girders/beams. This could easily result in k>2.
This sort of goes away with the new Direct Analysis Method.
RE: Maximum slenderness koef. for sway frame
RE: Maximum slenderness koef. for sway frame
1. The moment/rotation relationship in the base connection due to flexibility in the base plate.
2. The moment/rotation relationship in the base connection due to the flexibility in the anchor bolts.
3. The moment/rotation relationship in the base connection due to the flexibility in the footing on the soil.
These are many times very difficult to quantify and put in an analysis model, so engineers tend to assume they are pinned, allow the full rotation to occur, and design the frame above with rigid connections between columns and beams.
RE: Maximum slenderness koef. for sway frame
But what if I can model the footing beneath the column and also define subgrade reaction of the ground?
RE: Maximum slenderness koef. for sway frame
RE: Maximum slenderness koef. for sway frame
I havent done one in a while, but that is how I would still do it.
RE: Maximum slenderness koef. for sway frame
Im talking reinforced concerete structures here!