torsional buckling of a column with jib crane
torsional buckling of a column with jib crane
(OP)
I've been asked to look at the feasibility of mounting a 1-ton jib crane to an existing column. The column is a w10x49#, approx. 35 feet floor to roof, braced in X- and Y-axes at the top. In addition to eccentric loading, as the jib rotates, torsion will be induced in the column. AISC spec E4 refers to Kz, effective length factor for torsional buckling, but I can't find a value anywhere. Can somebody point me in the right direction?






RE: torsional buckling of a column with jib crane
I'd be careful about assuming warping restraint. I'd doubt that you had a condition at a conventional warehouse-type column top that would restrain warping. However, I'd think that your torque should be pretty minimal if you have some thrust bearings or greased bushings at the pivot of the jib.
RE: torsional buckling of a column with jib crane
RE: torsional buckling of a column with jib crane
RE: torsional buckling of a column with jib crane
We would have to see more details of what you are actually doing, and you’re way short on those so far. But, aren’t you really talking about column cap’y. due to significantly varying Mx and My as the boom rotates or the load moves to the end of the boom? Plus the added ton of vert. load, of course. But, what torsion? You can reinforce the column as needed and you want to put some sort of cushioned stops on swing and trolley movement on the boom. Also, consider that users will reach out and to the sides for picks so consider these possible lateral loadings.
RE: torsional buckling of a column with jib crane
This doesn't ring true. The pivot will be eccentric of the column, when the crane is swung to the side it will pull the top connection in one direction and push the bottom in the opposite direction. I can't be sure of this because there is, as dhengr noted, a dirth of information.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: torsional buckling of a column with jib crane
RE: torsional buckling of a column with jib crane
RE: torsional buckling of a column with jib crane
BA
RE: torsional buckling of a column with jib crane
RE: torsional buckling of a column with jib crane
RE: torsional buckling of a column with jib crane
RE: torsional buckling of a column with jib crane
Now that I see your details, I agree that there will be a torsional component involved in the design. I do not have the several guides or latest AISC code you are looking at. The torsion is just the lateral force at the pin times the distance to the centroid of the column section, irrespective of which orientation you are connecting to the column. The difference is that you have to consider two different connections, depending upon the orientation, to get that load into the column. Your plates welded to the flanges and the web, maybe with some stiffeners from the hinges base plates and/or to the column, should do the trick. Otherwise, the column doesn’t know the difference.
RE: torsional buckling of a column with jib crane
Do you have the ability to "box" the column by welding in plate on both sides in between the flanges, essentially making your wide-flange section into an HSS? If so you could greatly simplify your problem and reduce the possibility of overstress by introducing a closed section. Otherwise you may need to track down the original Jim Fisher & Steven Thomas paper and not the discussion, and re-derive for your specific orientation. Or, you could do a numerical analysis with a spreadsheet.
RE: torsional buckling of a column with jib crane
BA