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juneng (Structural) (OP)
22 Aug 07 12:08
I have a project that calls for the strengthening of existing open web steel joist in a roof for additional loading. The joist is comprised of double angle chords with diagonal rod webs - field measurements are the only information that are available in this case- no tags & no drawings.

Specifically, I am concerned about the shear capacity of rod web members. Can anyone provide a procedure, which they are comfortable with; to determine the shear envelope or capacity for the joists in question (similar to truss design?) that would provide me with the capacity of the joist?

For all methods of strengthening for which I have encountered it has been required to retrieve the ID tag / SJI load capacities for the joist. I understand that when the ID or load capacities are available, the shear & moment capacity envelope is generally easy to find & compare to the new loading conditions. But the info is not available to me in this case.

Thanks.
JAE (Structural)
22 Aug 07 14:12
You might look in the SJI specifications.  It provides the design parameters that joist manufacturers/designers use to develop the joist components.

Go here:  http://www.vulcraft.com/downloads.htm

And click on their JOIST Catalog to get a pdf of their catalog which I think contains the spec.

The other thing to worry about is not just the diagonal member capacity (which is just a mini-column with its own KL/r) but the weld that connects the diagonal to the chords.  That is the hard thing to verify (size and electrode-wise).

jike (Structural)
22 Aug 07 17:53
You also need to determine the yield strength of the material. There was a point in time where the webs were different in strength from the chords. I suggest that you work closely with SJI to help you make that determination.

I would be very surprised if there are no tags available. I have always been able to find tags!

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