Eccentric Connection to flange

[raystr2025]

Hello, I am looking for help in trying to figure out how to analyze the effect of the eccentric load on the rivets of a built-up section.

If you are able to see below, on the left side of the W36 beam there is a large room which cannot be disturbed. To strengthen the built-up girder that is resting on the existing built-up column, I introduced a W36 beam underneath to share in the transfer of the load on the structure from above (181 kips). The connection is to one flange of the built-up column with an e= 3.875 in. Through the calculations, it is introducing fb = 1.43 ksi.

A comment was made to provide documentation that the rivets in the existing built-up column (7/8" diameter, 5" center to center, column is 17 ft tall) would be able to take the eccentric load.

I have been thinking about it all day, and I am not sure how to prove this - would I have to use something like RAM/ Idea Statica? Any guidance would be very helpful!

 

[nategemb]

IDEA StatiCa could be a good resource for analyzing this. I'm not confident RAM Connection could run it properly.

 

[KootK]

This feels more like an equilibrium / fundamentals thing than an FEM thing to me. It'll be no mean feat though.

Over a relatively short distance near the beam connection, you need to plausibly turn that eccentric shear into three things, superimposed:

1) An axial load running through the column centroid. This means moving axial load from the loaded angle into the other three such that they share it evenly.

2) A weak axis moment. This implies weak axis shear. So you would also check the rivets for weak axis shear based on VQ/It.

3) A strong axis moment. This implies strong axis shear. So you would also check the rivets for strong axis shear based on VQ/It.

I don't envy you this. It feels like a half day's worth of work to me. But, then, I'd have to do some homework just to work out the shear capacity of the rivets as its been a while.

 

[Smoulder]

Free body diagram each component. Do localised stress at connection at one end of FBD and P/A + M/Z at other end when St Venant has evened it out. Difference is force in rivets to create equilibrium. Work out how many rivets and compare to 1 to 2 times section depth where the evening out wants to happen. If much longer then relying on rivet ductility.

 

[KootK]

I just clued into the fact that your connection has torsion. This will put some of your rivets in tension. I bet this is what your reviewer is concerned about. No weak axis flexure.

 

[raystr2025]

I just clued into the fact that your connection has torsion. This will put some of your rivets in tension. I bet this is what your reviewer is concerned about. No weak axis flexure.

thank you! yes I believe this is correct, I will try to calculate per rivet. due to construction schedule I had to provide a bolster to the column but I am going to continue looking into this. it wouldn't hurt to look up rivets since all I've worked with 4 years out school are bolts

 

[raystr2025]

Free body diagram each component. Do localised stress at connection at one end of FBD and P/A + M/Z at other end when St Venant has evened it out. Difference is force in rivets to create equilibrium. Work out how many rivets and compare to 1 to 2 times section depth where the evening out wants to happen. If much longer then relying on rivet ductility.

thank you!