modification factor for steel member

[swelm]

hi everybody

i want to ask about the modification factor for steel beams and columns when i used etabs program or what else

as per lrfd 99 and where i can get it in the code?

for example for concrete column as per aci 318-99
we make torsion factor 0.2 and moment of inertia direct 3 and 2 is 0.7
but for steel member i have not idea
any suggestion?

 

[csd72]

Is this factor for modifying the stiffness of the member used in analysis? If so then it only really applies to concrete and is taken as 1 for steel.

csd

 

[swelm]

thank you for your valuable information

 

[flyby911]

all the modifier factors in sap & Etabs for steel members are 1

when you design RC you design sections as cracked section according to ultimate limit state design so moment of inertias of all the RC members are lesser in the reality than that in the computer model which gives lower values of deflections and relatively wrong distribution of straining actions to members

but in structural steel no cracking occurs and the sections works in it's full inertia