Structural steel joists

[engrreddy]

How can we calculate capacity of existing steel roof joists ( 50+ years old)? Please help!!

 

[AELLC]

Are those SJI "J" series? I have the load tables in my AISC 7th Ed. manual.

 

[engrreddy]

I couldn't find any info. on the joists like tags etc., Please suggest how to classify them?

 

[BAretired]

You have provided very little information. Do you have any photos of the joists? A description of chords and web members? Any measurements? You might be able to narrow it down a bit, but there have been many joist fabricators over the years who used various grades of steel, so it is hard to be precise about joist capacity.

BA

 

[engrreddy]

The joists 14" deep and has double angle of 2x2x1/8" as top chord and 5/8" double rods as bottom chord with 5/8" middle/web rod. i have photos also. I will attach photos ASAP. Thank you for your time.

 

[MJB315]

If you go to the SJI website, they provide a form that you can fill out with joist measurements and project information. They check their records and come up with a "best guess" joist size, which you can then compare to historic records. They're very helpful.

"We shape our buildings, thereafter they shape us." -WSC

 

[UcfSE]

If you can't find any identification or help from manufacturers, you will have to survey the joist and analyze it on your own.

 

[nac521]

I agree MJB315. Survey the existing joists to get as much possible info to SJI and they may be able to help.

 

[engrreddy]

Thank you all for your time. If I have an RTU of approximately 700 lbs at mid span of joists, curb spanning between two joists, any info on how to check for overloading condition, if any or otherwise. Appreciate you all for your time and help.

 

[BAretired]

It is probable that the existing joists are not capable of carrying the RTU. Assume that and press on with the strengthening measures required.

BA

 

[tsaldana]

If the RTU is too heavy for the pair of joists, maybe you could spread the load over three or four joists instead of strengthening the joists.

 

[tsaldana]

If you can't find a comparable SJI joist in the historical tables, then you will need to analyze the joists. You could do it by hand or use an off the shelf FEM Program such as RISA-3d or RISA-2D to model the joists. The biggest problem is knowing what type of steel the joists are made of.

Or you can go to the SJI website and fill out the Joist Investigation Form and see if they can help you. The link is:

http://steeljoist.org/joist-investigation-form

SJI also has a link for the form so you can download it, print it, for when you go into the field and you won't forget what information you need to send them.

Anybody else have any other ideas? I hope that helps.