Angle Iron Analysis
Angle Iron Analysis
(OP)
I'm looking at hanging a large industrial fan from 3 x 3 x 1/4" angles. I have the static load of the fan and the torque from the manufacturer. In terms of stress analysis to make sure my angles are sized right for the 8ft span, I'm looking at bending stress (Mc/I) and shear stress (3/2 V/A). I'm not sure how to think about the torque, would that basically just be another bending stress at the connection point? The angles are bolted to bar joists. Thanks in advance.






RE: Angle Iron Analysis
isn't there some gyroscopic force associated with rotating elements ? maybe it's small, but ...
what about vibration, the natural frequency of the support structure compared with the speed of the fan ?
RE: Angle Iron Analysis
RE: Angle Iron Analysis
You're on the right path. Your stresses also are also dependant on the type of connection. I am assuming a welded connection, which would be best. You're moment diagram would be similar to the moment diagram of a horizontal cylinder mounted on two saddle supports. If you're bolting, then you'll need to account for the lost steel due to the holes.
RE: Angle Iron Analysis
RE: Angle Iron Analysis
RE: Angle Iron Analysis
RE: Angle Iron Analysis
Before you try doing a structural design problem like this, you may want to get out your old strength of materials and machine design textbooks, and then take a short course in formulating a good question. Some sketching might help too. With the little info. you have given and lack of a sketch, imagine the number of different hanging configurations we could conjure up, each involving a slightly different approach to the analysis, stresses, deflections, vibrations, etc. We can't see what you're looking at from here and you don't tell us.
The advice above isn't bad advice, but we are all guessing at what you are really doing; and given the way you asked the question, you don't really know either. You should be talking to your boss or a local, mentor, engineer on these kinds of questions; where you are both looking at the existing bar joist conditions and fan product sheets, and doing schematic sketches together, and some of your questions would probably become self evident, or maybe you shouldn't be doing this design problem yet. Where are you loading the bar joists? Are you overloading them? An 8' angle span btwn. bar joists seems kinda long to me. How do you attach the fan frame to the angles and what orientation do the angle have? Angles are an unsymmetrical bending shape so they can be subject the torsional issues, so you could be right on that account, but I'm not sure that's the torque you're talking about. But, this may not be a big problem depending on the connections and their relative locations. Mc/I & 3V/2A may not be exactly appropriate, but I don't think von Mises would give the problem a second thought.
You'll learn a lot more, and more quickly, if you can ask these kinds of questions of someone who is knowledgeable, and right there, to work intimately with you on these projects. If you can find those types of people, mentors, it can be quite a rewarding experience and exchange. Furthermore, your boss should know what you do and don't know, so he/she can keep you all out of trouble on this stuff. Good Luck.
RE: Angle Iron Analysis
BA
RE: Angle Iron Analysis
Agree with BA a picture speaks a 1000 words.
desertfox