unequal leg angle design - at a skew

[cmbyrd77]

Does anyone on here have experience with this type of single angle design (please see attachment)? My client is storming reams of aluminum coil stock on this storage rack and the angle serve two purposes, 1) to keep the reams from rolling and 2) to carry the load out to the support channels. My angle design experience has been strictly orthogonal, so this is bit challenging. Looking for any tips, advice, design lit., etc. Chapter F in the AISC doesn't really give much information on the matter. Thank you in advance.

 

[AELLC]

To me it looks like the angles are already very close to minimum Section Modulus orientation so I would compute bending stress based on Sz and limit allowable to 0.6 Fy (ASD)

I think you also have plenty of additional margin because the span of those angles are so short compared to their leg dimensions.

 

[BAretired]

My client is storming reams of aluminum coil stock on this storage rack and the angle serve two purposes, 1) to keep the reams from rolling and 2) to carry the load out to the support channels.

storming = storing, right?

Why unequal leg angles? Equal leg angles would be easier to calculate and would seem to accomplish the same result.

BA

 

[dhengr]

BA:
The advantage of the unequal leg angles is that they carry a smaller dia. coil at a preferred bearing location/line closer to the vert. axis through the center of the coil. While the equal leg angle will cause the preferred bearing lines to be at about 45̊ on either side of the vert. axis. And, this increases the radial load on the coil to carry its weight. If an aluminum, copper or brass coil, thin enough steel coil too, bears on one of the sharp edges of the angles it will get creased, a number of layers deep. You want the max. dia. variation of the coils to bear on the flat surface of the angle legs. All he has to do is take the load on the angle, and convert it to load components about x-x and y-y axes on the angle and treat it as a combined stress problem on the angle. As for a design improvement, I would bolt a pine 2x6 to the flat bearing faces of the angles, to treat the coil stock even a bit more gently.

 

[CELinOttawa]

I've had to deal with this in Milk Plant rack... Like Dhengr said, you just resolve the forces to the x-x and y-y plane and treat as combined bending.

 

[cmbyrd77]

Thank you, dhengr, and yes I meant to say "storing." I had thought about splitting the load into components, but really isn't the load already normal to the long leg only. So my first thought was to just check it for minor bending about the y-y axis. That is why I'm not sure if I agree with AELLC's concept of using Sz.

 

[AELLC]

The gravity load acts closely perpendicular to the Z-Z axis, so why bother with the extra step of resolving into X-X and Y-Y.

This is not like designing a major transfer girder in a high-rise, after all. To me, it is a minor design and can be done quickly, and being conservative won't create a lot of unnecessary tonnage of steel.