Why are there so many Modal Analysis Cases?

[osmanbayrak]

Hello, what are the 8 modal analysis cases in the default settings of the program for?

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What is the description of the situations here. I couldn't find the source in the manual or anywhere. Thank you for your interest.

 

[Ismail Hakki Besler]

If there is no rigid basement floor in your building, there will be 4 modal analysis cases. The reason there are 4 is that the masses are shifted +/- 5% from the center of mass to get the effects of eccentricity. If there is a rigid basement floor in your building, modal cases are defined for 4 basements in the same way. Thus, there will be 8 Modal cases in total. The program automatically decides on the modal analysis situations while analyzing, and if there is no basement in the building, the modal cases defined for the basement are not used. In accordance with clause 4.5.10.2 (d) of the Regulation, ideCAD calculates by shifting the floor blocks by 5% in the center of mass. This method is the method of obtaining eccentricity by dynamic procedure. Another method is to take the eccentricity as a static procedure and add it to the modal calculation. If you type "Accidental Torsion" in your search engine and search, you can find videos and documents related to both static and dynamic procedures here.