Plate design for HSS Column

[civilsf1]

Hello all,

I am fairly new to the Structural Engineering field.

I am currently working on an issue where in I have a column (exterior, HSS Column) which is sloped at 5.5 deg (According to Structural Drawings). But, apparently it was realised on the site that, the slope of the column is 4 deg.
In order to correct the problem they have proposed to cut the column and move it over by 3.25".
In order to do so they have provided a plate of size 1" (thick) 5"X12".
The problem being I need to provide the calculations for the eccentricity added due to the moved load on the plate and also on the base plate and the anchors.

Any suggestions on how to proceed for the same? Or let me know if I am atleast thinking in the right direction.

Thank you.

 

[CANPRO]

Not sure I can get a good visual on what you're describing (a sketch might help). But I think a good place to start is with a free body diagram of the plate.

 

[jdgengineer]

Check out AISC Design Guide #1. It's got good information for baseplate design.

 

[JoshPlumSE]

Are the anchor bolts located in the original locations? Is the offset in only one direction (resulting in a uniaxial moment on the base plate) or is the offset in both directions?

The reason I ask is because the resulting asymmetric arrangements may not be covered very well by AISC Design Guide #1. By all means start there and get a good feel for the calcs and the issues. Because you have to understand the expected / desired behavior. But, if you decide that the procedures in the Design Guide don't cover the more complex case that you're talking about then you probably want to give RISABase a try. Or, at least the demo version.

I don't want to give a hard sales pitch (I actually work for RISA). However, my belief is that RISABase is pretty unique among software solutions in its ability to handle these weird cases. Most other baseplate programs are just automated versions of the AISC Design Guide calculations. If you are interested, then below is a link to the RISA website where you can request a Demonstration version of the program.

http://www.risa.com/p_demo.html

 

[JoshPlumSE]

Another thing I should point out.... I don't think the angle of the column makes much difference to the base plate calculations. You've got a slightly different column geometry at the interface. But, after that, you're still just talking about axial force, shear and moment being imparted form the column into the plate and anchor bolts.

 

[msquared48]

Plus, with the original design at 5.5 degrees and the revised at 4 degrees (less), there will be less of an eccentric effect to the connection and column that originally designed. The original column and connection design should still be OK unless I am missing something here from your description.

Mike McCann
MMC Engineering