Flexural capacity of a column with Lb>Lr (360-05)
Flexural capacity of a column with Lb>Lr (360-05)
(OP)
now I am designing a column, 11.81x0.55 in flange and 11.81x0.31 web built up element. Its flexural capacity Mn, for Lb=118 in 2984 kip-in
for Lb=236 in Mn=2578 kip-in
and for Lb=354 in Mn=1967 kip-in
but for Lb=393.7 and although this dimension is bigger than Lr, Fcr=31.51 ksi (Fy=32.63 ksi)
And this leads to a bigger flexural capacity? (Sorry for dimensions, i converted them from SI)
Fcr*Sx is bigger than a value in a zone for Lp<Lb<Lr..
am I doing a mistake?Thanks.
for Lb=236 in Mn=2578 kip-in
and for Lb=354 in Mn=1967 kip-in
but for Lb=393.7 and although this dimension is bigger than Lr, Fcr=31.51 ksi (Fy=32.63 ksi)
And this leads to a bigger flexural capacity? (Sorry for dimensions, i converted them from SI)
Fcr*Sx is bigger than a value in a zone for Lp<Lb<Lr..
am I doing a mistake?Thanks.





RE: Flexural capacity of a column with Lb>Lr (360-05)
i use there formulas,
Lr=pi*rts√E/(0.7Fy)
Fcr=Cb*pi²*E/(Lb/rts)²*sqrt(1+0.078Jc/Sxho(Lb/rts)²)
h = 300mm 11.81103in
b = 300mm 11.81103in
tf = 14mm 0.5511814in
tw = 8mm 0.3149608in
Used values kip-inch
E= 210000 N/mm2 29000.00
Fy= 225 N/mm2 32.63
Fu= 340 N/mm2 49.31
G= 81000.00 N/mm2 11200
bf= 300.00 mm 11.81
tw= 8.00 mm 0.31
tf= 14.00 mm 0.55
h-2c= 300.00 mm 11.81
Ag= 108.00 cm2 16.74
I1-1= 22518.88 cm4 541.0194247
S1-1= 1373.10 cm3 83.79
r1-1= 14.44 cm 5.68
I2-2= 6301.28 cm4 151.3891846
S2-2= 420.09 cm3 25.64
r2-2= 7.64 cm 3.01
Z1-1= 1498.80 cm3 91.46
Z2-2= 634.80 cm3 38.74
J= 60.00 cm4 1.44150888
Cw= 1553202.51 cm6 5783.98543
rts= 8.28 cm 3.26
RE: Flexural capacity of a column with Lb>Lr (360-05)
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RE: Flexural capacity of a column with Lb>Lr (360-05)