Exist T joists @ roof
Exist T joists @ roof
(OP)
2 sketches attached.
I am dealing with a new RTU (aprox. 4000#) over an existing concrete T-joist roof. Ts are 20" deep, 30" oc. Each panel is 5' long with 2 Ts thus. The existing drawings show the moments for which the T manufacturer had to design for but I can't figure out two things:
1) The design moments shown on the existing drawings: I am assuming these to be factored, is that reasonable?
2) The moment call out does not clearly say whether this moment is for a single T or the whole panel (2 Ts). I am assuming this is for one T.
I am dealing with a new RTU (aprox. 4000#) over an existing concrete T-joist roof. Ts are 20" deep, 30" oc. Each panel is 5' long with 2 Ts thus. The existing drawings show the moments for which the T manufacturer had to design for but I can't figure out two things:
1) The design moments shown on the existing drawings: I am assuming these to be factored, is that reasonable?
2) The moment call out does not clearly say whether this moment is for a single T or the whole panel (2 Ts). I am assuming this is for one T.
Kaiser
RE: Exist T joists @ roof
Kaiser
RE: Exist T joists @ roof
If there is no date, do a dead load analysis for the tees, roofing and mechanical (look like double tees) and see what the moment is unfactored. Compare it to what is listed on the drawings.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Exist T joists @ roof
Both numbers work for the existing loads but are about 15-20% apart which makes my RTU calcs tricky.
Kaiser
RE: Exist T joists @ roof
What I can't understand is why the moments in one span are significant, and in the other span are almost nothing or negative. Am I reading that right?
Interesting configuration of the "lap tees", with the flange joint over a web. Never seen that.
RE: Exist T joists @ roof
Heck, I'll just check if the new stresses are within the 5% allowance and call it a day.
Kaiser
RE: Exist T joists @ roof
Kaiser
RE: Exist T joists @ roof
RE: Exist T joists @ roof
Kaiser
RE: Exist T joists @ roof
RE: Exist T joists @ roof
Adam Vakiener, P.E.
RE: Exist T joists @ roof
The - in 23 is too high to be a negative, and the decimal point is similarly because of the drawings being in that condition, as AVak pointed out.
But thank you so much for looking so carefully into it, it made me check the drawings again and be very very sure. Thanks again.
Kaiser
RE: Exist T joists @ roof
RE: Exist T joists @ roof