thread801-259595 To find the model 2

[Ankita Degaonkar]

thread801-259595
To find the model masses in SAP2000 we need weight or mass, but the Output file of Joint mass contains U1, U2, U3, How we can add those? because the Unit is KN-s2/m.
I am attaching the table, Please Help me.
Thank You

 

[wannabeSE]

I may not understand the question. To find the total mass participating in the U1 direction, add all of the U1 direction masses. For mass in U2 direction, add all of the masses in the U2 direction. Same for U3. To find the weight multiply the mass by gravity.

 

[JoshPlumSE]

Just to be clear, Mass is directional in a finite element analysis. So, there can be different mass in the U1, U1, U3 (and rotational) directions.

Usually, the mass is the same for all translational degrees of freedom. Therefore, I would suggest added all the U1 mass together. All the U2 mass together and all the U3 mass together. Each one of those represents the total mass of the structure (for the specified direction). And, they are likely to all be equal.

 

[Ankita Degaonkar]

Thank You very much wannabeSE and JoshPlum for making me clear in this point.
Can you please help me to find out Modal participation factor and Modal mass coefficient for a frame directly from SAP2000?
Thank You.

 

[JoshPlumSE]

I would start with a couple of simple examples (linear, not pushover).... Simple 3 or 4 DOF example. If you've got a good reference for Response Spectra Analysis, you should be able to use it's formulas to back out the SAP results.

Your equations in the other thread look basically correct. But, to do a more complex example, you need to know the mode shapes and those mode shapes should be mass normalized. I'm assuming this is what SAP provides, but I don't know. You also need the spectra accelerations and the mass matrix. Ideally, you'd also get the stiffness matrix.

It's not something that I've ever done with SAP, though I've done it with a different program. Though I was allowed to kill more hours on it than would normally be justified for a typical structural project.