1. Centrifuge Models Design and Execution: Some Practical Considerations Student Researchers: Gabriel Candia & Roozbeh Geraili Advisor: Nicholas Sitar University of California, Berkeley Department of Civil and Environmental Engineering

2. WHY CENTRIFUGE MODELING? 2 Advantages Correct scaling of stresses Repeatable and cost effective Ability to model large structures with reasonable boundary conditions Limitations and challenges Non uniform gravity field Need for high speed instruments Ability to reproduce recorded ground motions Boundary conditions OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION

3. 3 OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION

4. 4 OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION

5. 1.- INPUT GROUND MOTION DESIGN AND EXECUTION ISSUES 5 OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION Loma Prieta SC - 5% Damping Response Spectrum

6. DESIGN AND EXECUTION ISSUES 2.- INSTRUMENTS LIMITATIONS 6 OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION Accelerometers Strain Gages Disp. Transducers Pressure sensors

7. Acceleration Load Cells 7 OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION PCB Piezotronics 0.3-12000Hz Interface Load Cell 0-2000Hz Frequency (Hz) 2.- INSTRUMENTS LIMITATIONS

8. Earth Pressure Acceleration 8 OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION Tactilus Free Form 0-100Hz Frequency (Hz) PCB Piezotronics 0.3-12000Hz 2.- INSTRUMENTS LIMITATIONS

9. 9 Direct measurement  Pressure Cells  max ? OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION 3. OUR CHALLENGE - EARTH PRESSURE IN RIGID BASEMENT How to measure seismic earth pressure on rigid buried structures?

10. Indirect measurement  Strain Gages 10 M+ M- M+ M- OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION 3. OUR CHALLENGE - EARTH PRESSURE IN RIGID BASEMENT

11. 11 Trend from Pressure Cells Magnitude from Load Cells OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION Our approach  Replace roof and floor with Load Cells 3. EARTH PRESSURE IN RIGID BASEMENT

12. OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION 12

13. OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION 4.- BOUNDARY CONDITIONS – INFLUENCE OF MODEL GEOMETRY 13 Input acceleration Flexible Shear Beam Container

14. OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION 14 2nd ring 5th ring EFFECTS OF MASS ASYMMETRY

15. LESSONS LEARNED Equipment and Instrument Limitations Instrument frequency response is an important consideration. Earth Pressure in Rigid Structures Currently available pressure sensors do give direct measurement, but are inconsistent Use of redundant instrumentation is essential. Boundary Conditions Interaction with container can be an issue for large models Check plain-strain assumptions OVERVIEWEXPERIMENTS PERFORMEDDESIGN AND EXECUTION