Required Section Modulus
Required Section Modulus
(OP)
This is a very green question, but I'm going in circles here.
It's necessary to "beef up" a column supporting a cantilevered jib crane. The jib crane is capable of rotating a full 180 degrees, and the column supporting it deflects badly in the weak axis. I know I need to increase the section modulus in the weak axis in order to prevent this deflection. My question is -how can I calculate the required section modulus needed to do this?
Am I way off here?
Thanks for the help!
It's necessary to "beef up" a column supporting a cantilevered jib crane. The jib crane is capable of rotating a full 180 degrees, and the column supporting it deflects badly in the weak axis. I know I need to increase the section modulus in the weak axis in order to prevent this deflection. My question is -how can I calculate the required section modulus needed to do this?
Am I way off here?
Thanks for the help!






RE: Required Section Modulus
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RE: Required Section Modulus
a 2nd question, i think it's unlikely but could the load/moment be higher about the weak axis ?
Quando Omni Flunkus Moritati
RE: Required Section Modulus
If you have deflection limit, you can work it backwards. Max deflection of cantilever beam (UDL) is wl^4/8EI. once you get the moment of inertia I, you can get S by dividing it by the distance from the NA to the furthest point of the shape.
If you are talking about how to find calculate the section modulus of irregular shape, I suggest to use AutoCAD.
I hope this helps
RE: Required Section Modulus
Deflection at the end of the jib crane is a result of rotation of the column and deflection of the jib. Measure the deflection of the jib under a trial load (not necessarily the maximum crane rating). Calculate the cantilever deflection of the jib beam and subtract from the measured amount. That will be deflection due to column rotation, δmeasured . Decide how much deflection you consider acceptable.
Column rotation is directly proportional to load P and moment of inertia of column, Ic, so you must increase Ic (existing) by a factor (Pmax/Ptrial)*(δmeasured)/δacceptable .
BA
RE: Required Section Modulus
RE: Required Section Modulus
Alarm bells went off in my head when the first thing I noticed was the reference to section modulus instead of moment of inertia.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin