Dynamic Stiffness for Turbine Bearing Support Location - SAP2000

[Sannyboy]

Dear All
Greetings !!

I am analyzing a Table Top Foundation for Steam Turbo-Generator.
Steady State harmonic analysis in Frequency domain is being carried out using SAP2000 software for vibration response.
For the analysis of the equipment, the equipment supplier has asked for dynamic stiffness of the foundation at the supporting points (bearing locations)
at different frequencies. So, I need to provide such information to the equipment supplier from SAP2000.
Actually, I have read a lot of literature including basic theories and SAP manuals etc., tried a lot of options in SAP2000 but could not extract the output
as below which is obtained from NASTRAN software.
Kindly let me know how we can generate such information from SAP2000. Any suggestion is worth discussing. I tried stiffness matrix output from SAP2000 ( TXE , TXA etc files).

sample from NASTRAN : -

FREQUENCY = 2.050000E+01
C O M P L E X D I S P L A C E M E N T V E C T O R
(REAL/IMAGINARY)

POINT ID TYPE T1 T2 T3 R1 R2 R3
621 G 7.36E-07 -5.40E-08 -2.02E-07 3.12E-09 1.88E-07 -1.50E-08
-1.30E-06 -2.66E-08 4.23E-07 -9.32E-09 -3.50E-07 -8.27E-09
643 G 7.35E-07 -2.87E-08 1.10E-07 3.23E-09 1.87E-07 -1.64E-08
-1.30E-06 -1.28E-08 -1.61E-07 -9.41E-09 -3.51E-07 -7.98E-09
1079 G 1.79E-08 -8.29E-09 3.88E-07 -2.81E-09 4.95E-08 -3.69E-09
1.08E-07 3.59E-08 -2.95E-07 -1.21E-09 -2.85E-08 1.00E-09
1393 G 7.19E-07 1.37E-07 -8.04E-07 9.42E-09 2.42E-07 -1.65E-08
-1.30E-06 2.01E-08 5.15E-07 -1.02E-08 -3.90E-07 -5.61E-09
2717 G 6.78E-08 7.03E-08 3.40E-07 -1.82E-08 7.00E-08 -4.10E-10
5.32E-08 -1.89E-08 -2.78E-07 8.71E-09 -5.19E-08 -1.68E-10
2722 G 6.90E-08 7.05E-08 -2.78E-07 -1.83E-08 6.99E-08 -1.31E-09
5.20E-08 -1.98E-08 1.82E-07 9.78E-09 -5.22E-08 5.26E-10

1 621X APRIL 7, 2010 NX NASTRAN 8/30/07 PAGE 775

 

[stressed]

Your question is not stated very clearly, and you seem to be going down an unnecessary path in attempting to use stiffness matrix files. Dynamic stiffness of bearing locations often means that geotechnical engineers or geotechnical software determines frequency dependent stiffness (K) and damping (C) based on soil data. SAP2000 offers a frequency dependent link to account for frequency dependent support conditions if that's what you're looking for.

SAP2000 will not perform geotechnical calculations to determine dynamic soil properties K or C for boundary conditions, and I'm pretty sure neither will Nastran.

The analysis results that you show suggest a steady state harmonic analysis which SAP2000 can do. You can analyze an entire "sweep" of frequencies/machine speeds in one analysis using SAP2000's Steady state analysis, and if needed, you can utilize frequency-dependent links during steady state analysis. Steady state results will provide Real/Imaginary output results.

https://wiki.csiamerica.com/display/kb/Steady-state+analysis

 

[Sannyboy]

ok Got it. I am going to perform Steady State Analysis and set the output option to show displacement values at the bearing locations for different frequencies.

I hope Turbine vendor will agree


Thanks for the help. Always appreciate

Sunny