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Open Web Joist Girders

Open Web Joist Girders

Open Web Joist Girders

(OP)
I am determining the load capacity of a mezzanine for a client. The mezzanine is framed with open web bar steel joists bearing on Joist-Girders. I have measured the joist girders and SJI was able to determine that they are 22K9's.
The girder is another matter. SJI does not determines girder sizes from field measurements. I have measured the girder fairly accurately, but analyzing the entire truss is "possible", but will require a lot of time.
Is there any way to look up the capacities of the girder based on chord sizes and spacing?

RE: Open Web Joist Girders

There is no way to do that to my knowledge. If you do not know the girder designation, you are left with modeling it yourself. I would be sure to model with pin-roller supports since that is more common for the joist manufacturer to do it that way.

RE: Open Web Joist Girders

(OP)
I was afraid of that. I calculated the moment of inertia using only the top and bottom chords and ingoring the webs. From that I can determine the section modulus, and can then calculate the maximum bending moment using 0.6Fy for compression chord. I think using this approach my numbers should be conservative.
I came up with an allowable load that was greater than the allowable load for the bar joists that the girder is supporting, so in essence the girder is not the 'weak link".
I think that is about as rational an approach as I can get.

RE: Open Web Joist Girders

Except that it doesn't verify the shear capacity of the girder, right?

Getting the end diagonal web member cross sectional area might allow you to extract a vertical shear capacity as well.

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RE: Open Web Joist Girders

When this happens, I use field measurements to model the actual girder in analysis software.

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