Mass moment of inertia

[geodou]

When a diaphgram constraint is assigned to level joints, does sap2000 calculates automatically the mass moment of inertia of these joints? (In reference with the level center of mass).
Thanks in advance.



George D. Ntounis
Structural Engineer
Dip. National Technical University of Athens

 

[Shz713]

source of mass is defined based on the elements definition in material properties, then all of the mass are lumped at joints where CSI software (not only SAP2K) calculates the mass source. You can even assign the mass source from load cases as well. When you assign diaphragm constraint, all of the joints have same deformation. You could verify that by simple simulation of portal frame and then assigning diagram constraint for corner joints to see the difference in output of joint masses. More detail refer to CSI Reference Manual page 53.

Cheers

 

[geodou]

Thank you mohandes2018 for your reply. Am aware how sap calculates mass to joints. Have to check if there is a difference in the modal analysis modes with and without the diaphragm constraints. Especially the fundamental RZ mode. This mode is affected by the mass moment of inertia.
Thanks again.

George D. Ntounis
Structural Engineer
Dip. National Technical University of Athens

 

[Shz713]

No worries,

make use of base acceleration with low amplitude in the required direction to have better insight. In case you have defined time history load case, then I would recommend it as you can clearly specify damping and modal analysis techniques to be used.

 

[geodou]

Thanks for the tip.

George D. Ntounis
Structural Engineer
Dip. National Technical University of Athens