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Real-Time Hybrid Simulations
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  1. Real-Time Hybrid Simulations P. Benson Shing University of California, San Diego

  2. Better Known as the Pseudodynamic Test Method Early Work: Hakuno et al. (1969) Takanashi et al. (1974) Pseudodynamic:slow rate of loading; dynamic properties simulated numerically Institute of Industrial Science, University of Tokyo Hybrid:real-time testing; analytical substructuring;distributed testing and simulation; ……….

  3. Pseudodynamic Test Method Update and Displacement Numerical solution of eqs. of motion Test Frame Advance to next time step: i = i + 1 Simple concept but requires care to execute. • Precision of displacement control. • Accumulation of experimental errors in numerical computation.

  4. Experimental Error Accumulation Shing and Mahin (1982) Main source of systematic experimental errors: time-delay in servo-hydraulic loading apparatus

  5. Computer Model Update and Numerical solution of eqs. of motion Advance to next time step: i = i + 1 Substructure Test Methods Dermitzakis and Mahin (1985) Test Frame

  6. Range of Configurations

  7. Computer Model Test Base Isolation Devices Computer Model Test Active/ Passive Dampers Needs for Real-Time Tests

  8. General Framework for Hybrid Simulation Structural Partitioning

  9. Total Formulation

  10. Coupled Subdomain Approach Implicit Scheme Explicit Scheme Magonette et al. (1998)

  11. Dynamic Substructuring I

  12. Computational Model Actuator Specimen Actuator Shake Table Dynamic Substructuring I Sivaselvan and Reinhorn (2004)

  13. Dynamic Substructuring II

  14. Dynamic Substructuring II Actual Equipment Tested Horiuchi et al. (2000) Bayer et al. (2005) Bursi et al. (2008) Actuator Shake Table Computational Model

  15. Real-Time Hybrid Test Methods • Nakashima et al. (1992, 1999) • Horiuchi et al. (1996) • Tsai et al. • Darby et al. (1999) • Magonette et al. (1998) • Bayer et al. (2000) • Shing et al. (2002) • Wu et al. (2005, 2006) Explicit Integration Schemes Implicit-Explicit Coupled Field Analysis Implicit Integration Schemes

  16. Newmark Implicit Method for Time Integration

  17. Modified Newton Method

  18. Convergence is guaranteed as long as is positive definite (Shing and Vannan 1991). Modified Newton Method • Number of iterations varies from time step to time step. • Increment size decreases as solution converges. Problems for Real-Time Tests:

  19. Fixed Number of Iterations with Interpolation Shing et al. (2002)

  20. Response Correction and Update Compatibility Equilibrium a-Method

  21. Nonlinear Structure

  22. System Configuration NEES@Colorado

  23. Real-Time Substructure Test Platform Target PC –Real-Time Kernel OpenSEES Analytical Substructure Model Special Element SCRAMNet Card 1 Experimental Element/Substructure Actuators PID Controller SCRAMNet Card 2 Data-Acquisition Program Specimen Real-Time Processor

  24. Issues in a Real-Time Test • Actuator time-lag caused by dynamics of servo-hydraulic system and test structure. • Communication delays among processors. • Accounting for real inertia and damping forces. • Convergence errors in numerical scheme. • Interaction of numerical computation with system dynamics.

  25. Phase-Lag Compensation Methods PID with Feedforward Discrete Feedfordward Correction Phase-Lead Compensator

  26. System Model for Test Simulation

  27. Physical Test System

  28. System Transfer Function (Linear System) • Consider dynamics of servo-hydraulic actuators and test structure. • Communication delays. • Error compensation schemes. • Interaction of numerical computation with physical system. Jung and Shing (2006)

  29. Implicit Integration Scheme External Force Explicit Prediction Implicit Correction

  30. System Block Diagram and Transfer Function

  31. Physical Test System

  32. Validation with Simulink Model Error Correction:

  33. System Performance (PID Only)

  34. PID with Feedforward

  35. Discrete Feedforward Correction (DFC)

  36. Update and Numerical solution of eqs. of motion Test Frame Advance to next time step: i = i + 1 Inertia Effect in Real-Time Tests +

  37. Influence of Inertia Force Feedback

  38. Actual Test with Inertia Force Removal Mt/M = 4.7%

  39. Influence of Support Flexibility

  40. Nonlinear Structures (2-DOF, a-Method) Strain Hardening Strain Softening Convergence: has to be positive definite

  41. Simulation Setup

  42. Two-Story Frame

  43. Two-DOF Real-Time Tests

  44. Two-DOF Real-Time Tests

  45. Actuator Real-Time Substructure Test with a Single Column Test Column Analytical Model in OPENSEES

  46. Real-Time Substructure Test

  47. Test of a Zipper Frame Georgia Tech U. At Buffalo UC-Berkeley UC-San Diego/U. of Colorado Florida A&M

  48. Test Setup

  49. 80% LA 22 200% LA 22 Test Results

  50. Brace Response