03-09-2012, 10:26 AM
The difference is how the program calculate β. the β factor= axial load due to all dead load cases in combination(1.2SW+1.2WALL+1.2SDL / total axial load in combination (1.2SW+1.2WALL+1.2SDL+1.6LL).
IN first case you put all dead load inside combination named DEAD so the program consider β=0 because it find no dead load case (you replace the load case by combination)
In second case it calculate β=0.4504 .I2= 0.4/(1+β)*I2 gross=0.275785 Gross.
I2=.275785*200^3*900/12=165471595 mm4
Pc=π2*EI/L2=3309090 N
δns= cm/1-(pu/0.75 pc)=3.145
IN first case you put all dead load inside combination named DEAD so the program consider β=0 because it find no dead load case (you replace the load case by combination)
In second case it calculate β=0.4504 .I2= 0.4/(1+β)*I2 gross=0.275785 Gross.
I2=.275785*200^3*900/12=165471595 mm4
Pc=π2*EI/L2=3309090 N
δns= cm/1-(pu/0.75 pc)=3.145