*** WARNING:CMN PARAM INVALID FOR NATIONAL ANNEX

Question

I am designing a welded steel structure. 
 As structure is welded i have mentioned 
 CMN 0.5 to beams 
 CMN 0.7 to columns (fixed support at bottom of column and tied using beams at top ) 
 It is showing warning: 
 *** WARNING: CMN PARAM INVALID FOR NATIONAL ANNEX 
 I have used NA 2 
 Is my consideration regarding CMN parameter is wrong? 
 or there is no need to mention CMN parameter for NA 2 
 Please give suggestions

Seth Guthrie · Accepted Answer

According to the program help, CMN should be 0.5, 0.7 or 1.0. 
 CMN Indicates the level of End-Restraint. 
 1.0 = No fixity 
 0.5 = Full fixity 
 0.7 = One end free and other end fixed 
 I see it mentioned for several National Annexes, in the discussion of Elastic critical moment and imperfection, but not the Dutch one (help sections 7D.3).

Modestas · Answer

The “k” & “kw” referred to in STAAD output are the end restraint factors to be used to find out the C1, C2 and /or C3 factors to be used for Mcr calculations. The DD ENV version of the code allows k to have values of 0.5, 0.7 & 1.0. However some national annexes specifies the use of NCCIs documents. These NCCIs only consider the case where k & Kw = 1.0. Hence if the user specifies any end restraint condition that requires 0.5 or 0.7 STAAD will fall back to calculating C1 etc from DD ENV (with the warning) instead of using NCCI document.

Modestas · Answer

If you specify CMN 0.5 or 0.7, STAAD will use Annex F of DD ENV 1993-1-1:1992 code to calculate C1 instead of using NCCI document.