11-01-2010, 05:07 AM
Dear PANA2
1) actualy this 0.35 is the ratio (not exactly but nearly) of Mcr/Ma used in deflection calculations of ACI & PCA...(PCA is the same thing...its the explanation on ACI )....
2) Instead of doing detailed calculations of cracked moment of inertia for deflection calculations, we use reduced moment of inertia by using these factors....this 0.35 for beams is a common practice for beams in design industry...
3) just take an example of simply supported rect. beam as i said in my earlier post and calculate both deflections; by hand and by etabs...using 0.35 factor...they will give you same values with less than 1 or 2% error.
1) actualy this 0.35 is the ratio (not exactly but nearly) of Mcr/Ma used in deflection calculations of ACI & PCA...(PCA is the same thing...its the explanation on ACI )....
2) Instead of doing detailed calculations of cracked moment of inertia for deflection calculations, we use reduced moment of inertia by using these factors....this 0.35 for beams is a common practice for beams in design industry...
3) just take an example of simply supported rect. beam as i said in my earlier post and calculate both deflections; by hand and by etabs...using 0.35 factor...they will give you same values with less than 1 or 2% error.
WS