Joist bottom chord extension (to provide or not to provide)

[strucguy]

Per the language in the link below, a stabilizer plate shall be provided at each column to stabilize the bottom chords of the joists framing into the column.

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=12748

This makes sense when the primary members (i.e beams) are connected to the columns using simple shear connection. What is the approach one has to follow when you use a cantilever beam system, where the beams run over the columns (sort of like a continuous beam) and the secondary members (i.e joists) frame into this beam? Beam bottom flange stability is addressed by providing stiffeners in the beams web. Do we or don't we need joist bottom chord extensions in this case (per OSHA)?
Appreciate your help. Thanks.

 

[strucguy]

Can anyone comment on my argument above? Thanks in advance.

 

[OHIOMatt]

The purpose of the BCX as required by OSHA is to prevent the joists from rotating during erection. So yes, you must provide it.

 

[dhengr]

Strucguy:
OSHA and its convoluted verbiage and logic has always been an absolute killer for me, even while their primary intent is to keep people from being killed. They couldn’t just say ‘stabilize the tops of the columns in all directions during erection.’ In keeping with the current philosophy of code writing, they just can’t make it simple, they have to tell you where to locate a certain sized shackle hole. Then if this doesn’t work nobody knows what to do. Although this whole convoluted mess is because they are trying to protect so many dummies and their companies from themselves, because so few know what to do, or what they are doing, in any case.

Seems to me that the primary intent in para. 1926.757(a)(1) is to provide stability at the top of the columns, in both directions during erection. They say that if there are not beams framing into the column in two directions, then the joist at the column must serve that stability function. And, this would seem to be needed whichever way you suggest you might frame the beams which the joists bear on, into the sides of the col. or over the top of the col. It seems that in the latter case you might use the web stiffener as the means of fixing the bot. chord of the joist, and maybe the 13/16" shackle hole too. Alternatively, you might still need to apply some guying means near the top of the column, and at some columns in both (all four) directions. Get to know your local OSHA people, and if you find a good one, stay in touch, they can be quite helpful. They will listen to your side of the story before the disaster, they are tougher to deal with after the fact. Please ask your OSHA guy/gal, don’t take my word for it. They have the final say in their jurisdiction.

Quick story.... I was involved as an expert on a case involving a warehouse, about 600' x 800'; the steel was all erected, including most of the joists and most of the precast wall panels. But, they hadn’t gotten very far on the roof diaphragm yet. And, mother nature did her thing. When we walked in there you couldn’t climb through the mess of steel on the ground, and you had no frame of ref. as to where you were. The best and most revealing photos were taken from a crane basket high above the roof level. The way the joists, beams and columns laid on the ground pointed right to the spot. We climbed back into that spot in the bldg., and a half day’s work in one area was missing a few guy cables, and this was never noticed for the forest of columns and cables in the whole bldg. That’s the biggest pile of scrape steel I’ve ever seen, all perfectly painted and waiting to be cut up and hauled away, and nobody hurt either.

 

[strucguy]

OHIOMatt and dhengr

Thanks so much for your input. I have decided to go ahead and show joist bottom chord extensions at all column lines. I am assuming I can use the beam web stiffener to perform the function of stabilizer plate. Thanks.