Steel Bar Joists 1

[Structural Mindset]

Hello guys, one of my friends wants to know if she can hang around 700 pounds from a bottom chord of steel bar joist in her warehouse. It is one of those older warehouses. What is the right way to approach the matter?

 

[JLNJ]

Check the load path for the required strength(s).

 

[r13]

Get the type of truss, manufacture, date of installation, and check with SJI for design information. You might have to measure the truss yourself if information are missing. Also, I don't think joist manufacturer encourages hanging weight on the bottom chord. Get your hands on any of the joist catalog for recommendation on hanging concentrate load.

 

[dik]

I was going to write out a methodology, but it gets a little complex. Simplified: First add a channel or angle to the bottom chord spanning between the two panel points where the load is applied that is capable of supporting the 700 lb load. This would be the first step. You then need to check the existing capacity of the joist and loading and see if the existing (and future) loading are less than the joist capacity plus the added moment from the added point load. Best to check with a local engineer. Likely not an issue once the load is transferred to the panel points, but you need to check.

Dik

 

[Structural Mindset]

thank you guys.

 

[BAretired]

I would say the first step is to see whether the joist can carry an additional 700# load, with or without a beam between panel points. If not, how about spreading the load over two or three joists with appropriate framing between?

BA

 

[dik]

BART... that too.

Dik

Dik

 

[Structural Mindset]

BAretired, just check for the max moment?

 

[dik]

yup... but, you need to transfer the point load to the panel points on the bottom chord.


Dik

 

[Structural Mindset]

dik, what if i just tie it to the panel point itself?

 

[BAretired]

BAretired, just check for the max moment?

A proper check is to check both moment and shear. Either could be critical, depending on where the 700# load is located in the joist span.

dik, what if i just tie it to the panel point itself?

That would be best, but the connection should be checked to ensure that the load is properly transferred into the joist. A 700# load is not trivial for a steel bar joist designed and built without considering it.


BA

 

[r13]

Check deflection, end bearing.

 

[dik]

If you can place it mid span, it shares the load between two panel points... else one panel point is OK. Unless you have a 'chunky' bottom chord it's best not to load it directly.
The resulting moment diagram will be similar and moment forces will be similar, except for the loaded panel point.

Dik

 

[Structural Mindset]

got it.