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8 <br />NEW JOIST DESIGN: <br />D = 15 PSF <br />Lr = 20 PSF <br />W = 16 PSF DOWN / 26 PSF UP <br />D + Lr = 35 PSF <br />D + 0.75Lr + 0.75(0.6W) = 42 PSF -- GOV DOWN <br />0.6D - 0.6W = -17 PSF -- UP <br />DOWN: <br />w = 2'(42 PSF) = 84 PLF <br />L = SAY 14' <br />M = WL^2/8 = 2058 FT-LBS = 24696 IN-LBS <br />V = WL/2 = 588 LBS <br />CHOOSE (2)2X6 -- S = 2(7.56 IN3) = 15.12 IN3, A = (2)(8.25 IN2) = 16.5 IN2 <br />fb req = M/S = 1633.3 PSI <br />fv req = 3V/2A = 53.5 PSI <br />CHOOSE DF-L GR. #2 <br />Fb = 900 PSI <br />Fv = 180 PSI <br />Fb' = (900 PSI)(1.6)(1.3)(1.15) = 2152.8 PSI > 1633.3 PSI -- OK <br />Fv' = (180 PSI)(1.6) = 288 PSI > 53.5 PSI -- OK <br />UP: <br />M = 9996 IN-LBS <br />V = 238 LBS <br />fb req = 661.1 PSI <br />fv req = 21.6 PSI <br />lu = 168" <br />le = 1.68(168")+3(5.5") = 298.74" <br />d = 5.5" <br />b = 2(1.5") = 3" <br />Rb = 13.5 <br />Fbe = 3818.9 PSI <br />Fb* = (900 PSI)(1.6)(1.3)(1.15) = 2152.8 PSI <br />Fbe/Fb* = 1.774 <br />CL = 1.459 - 0.514 = 0.945 <br />Fb' = 2034.3 PSI > 661.1 PSI -- OK <br />Fv' = 288 PSI > 21.6 PSI -- OK