Stanchion Capacity with Short Plate

[andploc]

how to work out compressive capacity of the steel stanchion with various EI/EA along the member?

I am looking at strengthening, adding extra buckling capacity, to an existing steel member by welding plates perpendicular to flanges of ub column.

however I cannot attach a plate right from the bottom to the top of the member. There is a splice at approx. 800mm from the bottom floor beam and a cleat 400mm from the top.

The column is 4000mm long (continuous, in braced frame builing) and the stiffening plate can only be welded to the mid part of the column. hence 850mm from the bottom and 450mm from the top.

How to work out compressive capacity of the whole member?

thanks Andploc

 

[youngstructural]

This is a very complex question. I do not think you will be sufficient support online; You need to talk this through with other engineers at your firm. I would also recommend reading papers on this and similar topics on the AISC website.

There are two or three threads on this subject that you can search for on Eng-tips, however again I believe you need much more support that you can find online.

Good luck,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[normm]

andploc

If you have access to a computer program that calculates eigenvalues and modeshapes, I can suggest the following method :

1. Model the column with whatever geometry, partial-length strengthening plate etc you have.
2. Apply any arbitrary loading.
3. Get the lowest eigenvalue and load factor from the output.
4. The elastic critical load is the load factor x Whatever arbitrary load you started with.

I have used this method to test the values of some standard section columns and also some non-standard columns which are larger at mid-height than at ends.