Definition of Imperfection load & Design Procedure by program
What is Imperfection Load?
Vertical members like a column and wall are not actually straight due to construction imperfection.
This geometric instability may cause a problem in the safety of the column. Generally, geometric imperfections can be divided into two categories, global imperfection, and local imperfection.
Imperfection Load as per EN1992-1-1 & EN1993-1-1
The method to apply to structural design for each imperfection type is as follows.
Figure 3. Global Imperfection 
Figure 4. Local Imperfection 
Global initial sway imperfections are determined as a coefficient, Ф, which is multiplied by the vertical load of the structure.
How to create the imperfection loads in the analysis model
The above image is an example of how to calculate nodal loads to finally implement imperfection.
The imperfection coefficient, Φ was entered by a user-defined method.
Figure 7. Example of how to calculate global initial sway imperfections (Φ)
The above image is an example of how to calculate global initial sway imperfections(Φ) and nodal loads to finally implement imperfection.
**** Note.
The error between the values by manual and by the program is due to the number of decimal points.
Tutorial to create the imperfection load in Gen / nGen
How to create the imperfection load in MidasGen
The procedure of creating imperfection loads in Midas Gen is as follows.
Step 1 . Calculate the coefficient, Ф
Step 2. Calculate Imperfection Load
Step 3 . Create Load Combination
Step 4. Check Imperfections in the table according to EC.
How to create the imperfection load in Midas nGen
The procedure of creating imperfection loads in Midas nGen is as follows.
Step 1 . Calculate the coefficient, Ф
Step 2. Calculate Imperfection Load
Step 3 . Create Load Combination
