SJI Joist Investigation Submittal

[SteelPE]

Has anyone submitted an existing field measured joist for analysis by the SJI? On their website you can fill out a form of the measurements taken while onsite (such as chord sizes, joist spacing, seat depth, bridging type, truss type etc). Within a day or so they come back with what they think the size of the joist is. I am wondering how reliable this service is and how often it is used?

 

[JedClampett]

What other choices do you have?

 

[SteelPE]

You could run your own analysis of the joist too verify what the capacity is. I would think the SJI would be better, but I don't know how accurate their analysis is. You put in some information and they tell you what the joist most likely is. I am just not sure how accurate they are.

 

[Once20036]

In my experience, it's not worth the time.

If you tell them you have a 28" deep joist circa 1960, they go into the historic specs and tell you that it was the weakest available 28" deep joist from that time period.
Comparing their results to my own analysis, i've found 2-3 size busts between their information and my results.

 

[SteelPE]

I just had an evaluation done on a joist and it appears as if they returned a really light joist for the application.

I have the 75 year manual which has a chart that give the approximate chord size for the measurements taken in the field (field measurements yield a 10). In this instance they are saying the joist has a chord size of 5. Back figuring capacity based upon the capacities of the top chord, bottom chord, end diagonal and first compression diagonal yields chord sizes closer to the 75 year chart (chord size 10).

I have used their service before and haven't really questioned yet, but now I am beginning to wonder how accurate it is.

 

[RickyTickyTavi]

Eh. I gave them a year, joist depth, chord size and diameter of the web. They gave me 3 joists, 1 of which wasnt manufactured at the time. I think theyre decent from 1980 to now... but the older ones I trust them less.

 

[GerryBertier]

I've used it many times over my 10 years as a consulting SE. Usually the managing director will respond and discuss his thoughts, provide tables, potential options, any additional information required.

Very prompt and have had a couple phone conversations picking his brain about this or that.

I'd highly recommend.

 

[gte447f]

Like GerryBertier, I have had good experiences with the SJI joist investigation form service on the few occasions when I have used it. However, you should not expect a definitive answer from them as to exactly what joist designation you are dealing with or what the joist capacity is, because I don't think they perform a structural analysis; I think they only compare the information that you provide to them against tables and other data that they have of structural member sizes, etc. that were commonly used by SJI member manufacturers at the time in question. My understanding is that member manufacturers have flexibility in how they design and assemble a joist to meet the SJI specification (i.e. it is basically a performance spec), so it is possible that there could be a bit of variability between different member manufacturers for a given joist designation. Because of this variability and incomplete information, they simply give you their best educated guess as to joist size and designation, and they are probably rightly conservative with their approach. As an engineer evaluating existing joists I also lean toward conservatism for the same reasons.