1. Characterization of C Pod
Measurement Report on Vibration Isolation of C Pod
Department of Physics, University of British Columbia, Vancouver PI: Dr Yan Pennec
Student: Vincent Wong

2. SolidWorks model – C Pod
Suspended by 4 isolators (Model #)
Volume: m3 Density: kg/m3 Mass: E4 kg % Concrete: 94.5%
Young Modulus: 3.94E10N/m2 Poisson Ratio: 0.17

3. Concrete Block Properties Deduction from Threshold Pressure
Isolator Dimension
Chamber Diameter: 15.7in
Total Effective Area: in2 * 4isolators
Threshold Pressure: 89psi
Threshold Supporting Force: lbf
Equivalent to N
Measured Mass: kg
Measured Density: kg/m3

4. Experiment Protocol - Slab Excitation
Reference Accelerometer
Data Point

5. Slab Excitation – Acceleration Amplitude z-axis damping for the slab
Time Constant ~100ms
y = A1*exp(-x/t1) + y0
y0= ms-2
A1= ms-2
t1= s

6. Slab Excitation – Average PSD in z-axis(1-1kHz)

7. Slab Excitation – Average PSD in z-axis (200-400Hz)
Twisting 1
Bending 1
Bending 2
Flapping support

8. Modal Resonance - Twisting Mode
Measured 228Hz
FEA 233 Hz
(1st mode in FEA)

9. Modal Resonance - Bending Mode
Measured 289Hz
FEA 283Hz
(2nd mode in FEA)

10. Modal Resonance - Flapping Support Mode
Measured 338.5Hz
FEA 340Hz
(3rd mode in FEA)

11. Damping by Isolators – x-axis acceleration amplitude
Time Constant ~14.9s
Natural Frequency ~1.02Hz
y = A1*exp(-x/t1) + y0
y0= ms-2
A1= ms-2
t1= s

12. Damping by Isolators – y-axis acceleration amplitude
Time Constant ~11.5s
Natural Frequency ~1.02Hz
y = A1*exp(-x/t1) + y0
y0= ms-2
A1= ms-2
t1= s

13. Damping by Isolators – z-axis acceleration amplitude
Time Constant ~2.14s
Natural Frequency ~1.4Hz
y = A1*exp(-x/t1) + y0
y0= E-4 ms-2
A1= ms-2
t1= s

14. Transfer Function in z-axis - Isolators

15. Transfer Function in z-axis – Room Isolation

16. Seismic Vibration in z-axis – velocity PSD open room

17. Seismic Vibration in z-axis – velocity PSD closed room (1 hour run)

18. Sound Pressure Level – closed room

19. Sound Pressure Level – Excited
19Hz
38Hz
25Hz

20. Acoustic Resonance Assumption: speed of sound = 350m/s
Expected Resonance Mode:
3.5m -> ~47Hz
3.8m -> ~43Hz
4.8m -> ~36.5Hz
5.2m -> ~31.7Hz
5.9m -> ~29.6Hz
6.1m -> ~27Hz
7.1m -> ~24.6Hz