where can i get old steel joist tables

huangyhg

where can i get old steel joist tables
doing a calculation for loading of hvac units on the roof of an old building (circa 1950?).  no id tags on the steel bar joist trusses and cannot find anything in stuff out there today.  
does anyone know where i can get old info?  for reference, the subject trusses are 38' long, 24" deep, contain 17 joist spaces and are constructed with 3/4" steel bars (including the bottom chords.
steel joist institute has a 75 year manual of old joists.
refer to their web page to order.
sji can also help you identify old joists by submitting a form with all the info. that you have.
another approach is to measure the geometry and model the joist in a program like risa or staad.  generally this will give you a conservative capacity, with regards to the load tables.
the loads tables can give you a range, but unless you have the joist tag or original shop drawings it's a crap shoot, the modeling works best.
for uk sections, i would recommend you have a look at 'historical structural steelwork handbook' published by bcsa.