Hanging L-Brackets Connection Analysis

[Tgoodman]

Have a custom application for a bracket assembly to be hung off clips welded to a large crane girder for access to replace parts. Basically an angle inserted into a laser cut HSS and welded everywhere possible, which will then be hung off the welded brackets on the girder itself with plank in between to create platform and railings. Beyond FEA analysis, having some difficulty conceptualizing failure mode and guiding calculations for this connection beyond some Force/Area calcs and weld checks. Any thoughts would be much appreciated.

 

[Tgoodman]

Just bumping to the top to see if I can get any thoughts. Thanks.

 

[ldeem]

Just some comments in no particular order

Radius the inside corner cut.

Regardless of analysis results I wouldn't go any less than 1/4" wall on the HSS.

Material cost is small so I would figure what is needed statically and then double it.

If you have room on the girder make it longer, I wouldn't go any less than 6".

Don't forget to look at the crane girder, if I understand your design it will put a torsional load in the girder. You need to check the deflection of your bracket as small rotation may make for an unacceptable deflection on the plank.

 

[MegaStructures]

Definitely check bearing/pullout of the pin in the blue HSS portion, bending of the blue HSS wall, and pin shear strength.

If you're designing the green piece I can see the bending/shear capacity of the mating part being a limiting factor. Is the green piece cantilevered, or is it supported on the opposite side?

“Any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands.”

 

[Tgoodman]

Green tubes are cantilevered, 2' span out supporting plank. Currently I have the bending of the blue HSS wall as the limiting factor, somewhat limited with HSS and tube selection with sizes stock to manufacturer but overall the current design is adequate with a beefy FOS. Just wanted to double check I'm not missing any connection checks on something I have not used before. Thanks for the input.

 

[MegaStructures]

That makes a lot of sense to me Tgoodman. The components in the "mating connection" seem much less robust than the body of the green tubes and it seems like you've covered all of the failure modes there with pin pullout/shear, HSS wall bending, and mating part bending/shear. I would still check global bending of the green tube and pipes for completeness as well as weld strength between each part. Is there any possibility for fatigue loading on any of the welds? I can't offer assistance there, but might be something to think about.

If it were me I would still run an FEA simulation, but I just like the extra practice and it doesn't hurt.

“Any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands.”