Industrial mixer support structure
Industrial mixer support structure
(OP)
An old agitator (mixer) was replaced from a side motor unit to an in-line vertical motor. The support structure (2-W10x33, 4.25' between them, 16' span) was deemed acceptable. According to my observations, the beams are rotating 8~10 degrees and this is a concern.
I reviewed the beams cpacity for static loading (floor, agitator components, etc) and they are fine. I calculated the dynamic torque and the bending moment at the shaft.
Here are my questions: Are the dynamic torque and bending moment applied to the support beams? What is the limit for the rotation of the beams? How do I determine the distance between the compression flange lateral supports?
Please help,
I reviewed the beams cpacity for static loading (floor, agitator components, etc) and they are fine. I calculated the dynamic torque and the bending moment at the shaft.
Here are my questions: Are the dynamic torque and bending moment applied to the support beams? What is the limit for the rotation of the beams? How do I determine the distance between the compression flange lateral supports?
Please help,






RE: Industrial mixer support structure
It is reasonable to assume that the dynamic torque will be transmitted to the motor base and to the support, and this should be taken into account in the design of the beams.
Steel W beams can develop their full section capacity only if they are laterally supported, to prevent buckling of the compression flange. In this case, the span is longer than the required distance between lateral supports of the compression flange, and as a result the beam has rotated.
The limit of rotation of the beam is an angle such that the angle is equal to the tangent of the angle, i.e. a very small displacement.
The distance between lateral supports is a function of the bending moment, beam dimensions, span, and the radius of gyration of the beam section.
RE: Industrial mixer support structure
I direct you to read the AISC design guide number 11 on open section torsional analysis. If you are AUSC member, you can download it from their web site www.aisc.org or you can buy it on line or fro their book store.
Torsion is a monster. I avoid it as much as I can. The best way to get rid of torsion is eliminate it, if possible.
Also consider fatigue stress due to cyclic loading. Make sure that you have vibration isolators.
You can brace the beams by using horizontal members or box them by suing floor plates on top and bottom.
Good luck