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Showing results for tags 'modifiers'.
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Hello I have a question regarding stiffness modifiers in ETABS. The code(ACI318) specifies us to use stiffness modifiers for walls column etc. What if I use 0.35 as stiffness modifier and not 0.7. What is the effect.I know that we have these stiffness modifiers based upon cracking of section and using these modifiers results in lesser stiffness thereby reductions in attraction of lateral forces.But suppose I want to reduce the lateral forces on walls therby using stiffness modifiers 0.35 for walls and not following the ACI. Thanks
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aslamwalekum , when we design reinforced concrete elements , for beam we take 0.35 , for column and wall we take 0.7 and for slabs we take 0.25 as modifiers , but i read in aci that for servicibilty analysis these modifiers has to increase by 43% which means for beam it become 0.5 , for column and shear walls it become 1.0 and for slab it become 0.35 , by doing this model drift and deflection both reduce to almost half of its original value. one thing more when we do manual check we dont take crack sections , for e.g for simply supported beam the deflection is 5\384 WL^4\EI , here the I (inertia ) is not the for the crack section ,its for the uncracked section , so what modifiers should be use 0.35 or 0.5 or 1.0 -
What could be the purpose of reducing raft stiffness by 60% (m11=m22=m12 modifiers of 0.4) in SAFE Model?
