Moment Envelope for LH Joists

[mateogrin]

I have an old LH Joist from the 1960s that I need to try and see if it matches some new loading conditions. I would like to check the moment envelope, but the 75 year joist manual doesn't seem to have any moment information for this kind of joist.

Does anyone have any suggestions, or know if I'm just missing something in the 75 year old joist manual?

Thanks

 

[jike]

Is the joist size listed in the catalog? Does it have a standard SJI designation? If so, you should be able to get an idea of moment capacity by using the uniform load to calculate the allowable moment. You then have 2 ways of analyzing the new condition: Compare the original moments and shear to your new moments and shear. The other way is to field measure all the members and welds and analyze it for the new loads.

If data is not avaliable in the 75 year SJI book, it may be one of those that was not fabricated to SJI standards such as was fabricated by Macomber.

You may also try to contact SJI and give them all the data and they might be able to guide you.

 

[mateogrin]

It is a 32LH06. It is listed in the 75 Year SJI, but it doesn't give any information about the joist's moment capacity. I have used the loading information back-calculated the moment, but I was hoping to find something a bit more accurate along the length of the joist.


Unfortunately, there is not enough budget in the job to go out and field measure and model the joist to get that kind of information.

Thank you for the response!

 

[jike]

In that case, I would use the first approach: Create a spreadsheet and calculate the original moment and shear say at say 20 points along the joist and then compare those with that for the new loading condition. Take a careful look at where the shears increase or where there is stress reversal. Reinforce web memebers as necessary. If the chords are parallel and one piece then the moment capacity should be equal along its length until the end panel.

Another option to reinforcing the existing joist would be to add a new joist alongside. I would often use a joist field spliced at the mid-span to make it easy to erect in an existing building.

Good Luck!