Stress in bottom flange of beam
Stress in bottom flange of beam
(OP)
I want to calculate the stress in the bottom flange of a beam that supports a trolley and hoist. I have already checked the overall beam for bending, shear and bottom flange bending per CMAA #74. The problem is that there is an existing group of bolt holes immediately adjacent to where the wheel passes, so I need to look at a VERY small area and am not sure how to proceed. Now I need to nail down the point at which the load is adjacent to the bolt holes. I have attached a sketch which shows the scenario. The classic kicker is that this hoist has been operating like this for 20 years or so without any visible deflection or damage adjacent to these bolt holes. Please help.





RE: Stress in bottom flange of beam
StrykerTECH Engineering Staff
Milwaukee, WI
http://www.stryker-tech.com/
RE: Stress in bottom flange of beam
Tara
RE: Stress in bottom flange of beam
If you do worry about fatigue, then I'd keep the combined bending stress below the endurance limit for Kt = 3.
RE: Stress in bottom flange of beam
StrykerTECH, the load on the trolley is 4.3K, which translates to 1.08K per wheel passing by the holes. The allowable stress is .66fy or 23.8ksi. The beam span is 63".
There are two reasons why I want to know the stresses, even though it has been operating for 20 years. The first is so that I understand why it works, when it looks so suspect in application. The second is because I am load rating this frame and so I want to be sure I am confident in its continued safe operation.
Unfortunatey I do not have a copy of Peterson's book. If you think it a valuable work to have on hand I will pick one up.
RE: Stress in bottom flange of beam
but these days there are plenty of (free) on-line Kt calculators.
RE: Stress in bottom flange of beam
RE: Stress in bottom flange of beam
Simple solution would be to weld a doubler plate underneath, and then shoot whoever didn't stagger the holes.
Cheers
Greg Locock
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RE: Stress in bottom flange of beam
The bending load, however, is fairly straightforward - I'd start with that for a hand calculation and then do an FEA for a more refined answer.
RE: Stress in bottom flange of beam
StrykerTECH Engineering Staff
Milwaukee, WI
http://www.stryker-tech.com/
RE: Stress in bottom flange of beam