I just remembered. The approach I offered will work for any K-Series joist. For S,J,or H-Series, it will work as long as the span of the joist under consideration is greater than the critical span. The critical span of pre-K-Series joist is denoted by a heavy horizontal line in the load table...
The age of the joist is very important. There are still joists around that were made with A7 Steel with allowable stress of 18KSI. Also lots of J-Series with allowable stress of 22KSI. You may be able to extract a coupon for analysis without destroying the joist, possibly the end of one of the...