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May be my questions seem stupid but just for the sake of disucssion today I have posted this to Mr. Arshad Khan, Civilea forum and SEFP forum. Looking forward to arrange all the answers by you guyz and write a tutorial Dear all, I have following question regarding slenderness in ETABS 1) Why moment magnification method and 2nd order elastic method both are used by ETABS. I mean in ACI there are 3 methods to do (any of them) then why we put modifiers and then ETABS calculates internally the moment magnification factors. 2) If structure is braced then how to stop etabs from calculating moment magnification? 3) If drift limits are defined for example in ASCE H/400 then why is the need to perform P-delta. If we control the drifts to be H/400 still we need to perform p-delta? 4) We take wind drifts for 10 year return period. that is multiplying 0.7 to W of 50 year year..to convert this into service level....What type of modifiers are required to be put in ETABS to take drift or deflections on this 10 year Wind.. Serive modifiers Beam=0.5 & Column=1.0 or Ultimate modfiers Beam=0.35 & Column=1.0 I mean as per ACI we can multipy the deflections from ETABS to 1.43 if we use strength level modifiers?