Angle Iron Analysis - Structural engineering general discussion

Lexenger:
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.