bj series jois

huangyhg

bj series joist
i recently made a site visit to an existing building constructed of steel beams and columns supporting a slab-on-metal deck and steel bar joists.  the joists are fabricated differently than what i've seen previously.  the top and bottom chords appear to be cold rolled plate steel instead of rods or angles.  the joist tag on several joists show "18bj7".  anyone familiar with a bj series joist?  i am not familiar with that and it does not appear in the sji 60 year manual as far as i can tell.  i am still researching but if someone has a clue, i'd appreciate the help.
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you should try the joist investigation form thru the steel joist institute.
is it possible that you are looking at a butler building floor?  they fabricate joists with a cold-formed top and bottom chords.  i can't tell you anything about the tag.
archeng59:
fwiw: i've been told by a joist engineer @ vulcraft that the first number (or 2 numbers in this case) on a joist tag are the joist depth, but the letters or numbers following that are just the manufacturer's piece number for that project so they can get all the identical joist on a project bundled together for delivery.
the letters/numbers following the depth do not indicate anything about the chord size or capacity of the joist. for that, vulcraft has to look up the joist bill of material for each project.
this may only be vulcraft's way of tagging their joists and may not apply to other suppliers.  
lkjh, thanks.  i knew that about vulcraft joist tags, but i do not believe these are vulcraft joists.  at least none that i have ever seen before.  
stevegregory, thanks.  i will check into that.
i am trying to find out when the building was constructed.  i was told the building was a two story parking garage previously, and was converted into a two story office building by adding the roof framing.  both the roof joists and floor joists are fabricated similarly, but different depths.  nothing about this building appears to be a former parking garage.  at least none that i've ever seen.