effective length of column
effective length of column
(OP)
Please tell me how to calculate effective length of column for an industrial building where in one direction it is connected by truss at the top only and on the other direction transverse beams. Shall we consider the total height of the column from the truss level to floor or the intermediate transverse beam center to centre for considering effective length






RE: effective length of column
1. It is conservative to do so for slenderness/buckling computations
2. Any load (from transverse beam, etc.) below the primary load at the top of the column is just an auxiliary load; i.e., it doesn't matter if it is a beam load or if you're hanging widgets off the side of the column...it is just another load on the same axial member.
RE: effective length of column
If the traverse beam is lower than the truss and also provides a bracing force to prevent buckling, wouldn't it serve to stiffen the column and have an effect on the calculation?
Or is it standard practice to iqnore the lateral bracing effect and just add the additional vertical load to the column support and buckling calculations?
Don Leffingwell
RE: effective length of column
I would neglect the beam if it weren't fastened such as to prevent lateral movement of the column.
The only other reservation I have is during construction. Is it possible to complete the roofing prior to placing the floor framing...in that case I would definitely use the entire column length.
RE: effective length of column
You are correct that it could provide some bracing, but we usually don't consider the affect unless in more than one direction (as Qshake alluded). Unfortunately, we are giving simplistic answers to partial scenarios. With more info we could probably consider more affect, though not always.
RE: effective length of column
therefore necessary to consider the effective length in the two directions
and compute the K*l/r factor for the two directions and take the worse
of the two. Note that 'K' depends on the restraint provided at top and bottom.
So, just consideration of a length alone may not suffice. You may have lateral
diagonel bracing (wind bracing) as well in Industrial structures. That will
reduce the K to 1.0 whereas the truss at the top may not provide a lateral
restraint at the top in that direction and you may need to use a K of 2.0 or 2.1.