column design manually and y sap2000 differnece

[ash11235]

hi,
In my building there is a huge difference between the reinforcing area recquired when designed by sap2000 and manually by IS 456.can anyone tell me why?and how to solve this?

[Cake of Doom]

Which method are you using to asses the minimum area for reinforcement in you hand calcs? Is the difference greater than required or less than, according to hand calcs? Have you looked at SAP's analysis to see how it arrived at it's conclusion?

This is like telling a doctor that you simply don't feel very well, without telling them the symptoms.

[ash11235]

the required reinforcement is always less in my hand calculations than that provided by sap2000.Yes,I have seen saps method, it does not provide the detailed method that it uses but the values of moments and axial force used by me as well as sap are also similar.so,I don't understand why there is a difference.

[Cake of Doom]

Is SAP taking the cracking reinforcement as a separate issue and adding more metal, rather than looking at the adequacy of the re-bar that's already in to perform for both roles? That seems to be the reason I mostly come across for design suites doing this.