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Re: Bar Joist

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I haven't seen any replies, so I'll put in my $0.02:

I don't (bother to) account for load sharing.  Usually I'll just decrease the spacing to account for the added load at the perimeter, since I think it's cheaper to buy an extra 4-6 joists of a series that you're already building 100 of instead of adding 2 or 3 joists of a unique type.  You could do a deflection/stiffness analysis to get a more accurate picture, but you have to be cognizant of the price of engineering analysis vs the return in the field (and whether or not you're getting paid to do the added scope).

For non-composite concrete floors, I count the concrete like it's sand - no stiffness, just dead weight. If it won't actually span the distance , it's the only prudent thing to do. The advantage to this "method" is that there actually is some residual load sharing that will occur when some numbnut does something stupid to the structure. Instead of collapsing, the floor system just sags locally or you get cracks in hard surfaces.
Jordan


Wesley Werner wrote:
    When you distribute roof loads to your bar joists, do you consider the continuity of the metal decking, or do you figure the decking is pinned between joists? Continuity makes a big difference particularly for the second joist from an edge where there is snow drift. In addition, what about floor loads when you have deck with concrete?

Wesley C. Werner

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