REAL-TIME DYNAMIC HYBRID TESTING OF STRUCTURAL SYSTEMS

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1 REAL-TIME DYNAMIC HYBRID TESTING OF STRUCTURAL SYSTEMS Mettupalayam V. SIVASELVAN PhD Project Engineer, G. E. Brown Network for Earthq. Eng. Simulation n (NEES) Andrei REINHORN* PhD, PE Clifford C. Furnas Professor Zach LIANG, PhD Project Engineer, G. E. Brown Network for Earthq. Eng. Simulation n (NEES) Xiaoyun Shao, PhD Candidate Project Engineer, G. E. Brown Network for Earthq. Eng. Simulation n (NEES) Department of Civil, Structural and Environmental Engineering University at Buffalo * Presenting Author

2 Outline Objective of Testing Feasibility issues Implementations Possible Applications Remarks INTERFACE FORCES ACTIVE FEEDBACK FROM SIMULATED STRUCTURE APPLIED BY ACTUATORS AGAINST REACTION WALL REACTION WALL SHAKING TABLES (100 ton) SIMULATED STRUCTURE FULL OR NEAR FULL SCALE TESTED SUBSTRUCTURE Fig.1. Real-Time Hybrid Seismic Testing System (Substructure Dynamic Testing)

3 Real-time dynamic hybrid testing Well understood ` Structural Actuator Foundation Focus of interest Laminar Soil Box Shake Table

4 Real-time dynamic hybrid testing Response Feedback ` Distributed mass Acceleration input: Table introduces inertia forces Foundation Laminar Soil Box Shake Table Structural Actuator Has to operate in Force Control

5 Real-time dynamic hybrid testing Combined use of earthquake simulators, actuators and computational engines for simulation Response Feedback ` Computational Substructure Physical Substructure Physical Substructure Structural Actuator Computational Substructure Shake Table Ground/Shake Table

6 Objectives of Hybrid Testing Allow testing of full size structures or substructures Allow to test strain rate effects Allow to develop inertial effects in distributed mass systems Test integrally the computational tools as well as the physical specimens Ultimately allow production of computational tools validated by experiments

7 Relation to state-of of-the-art Sub-structured pseudo-dynamic dynamic testing (Mahin, Shing, Nakashima) Mass simulated computationally Rate-dependent effects simulated predominantly computationally Algorithms and error analysis well-researched Sub-structuring displacement-based (interface displacements applied to specimen) Effective-force force method (Mahin, Dimig et al.) Ground acceleration applied as equivalent forces using actuators Actuator-structure interaction significant problem (French et al.) Shake-table testing (Reinhorn et al) Table-structure interaction addressed using iterative and adaptive techniques (MTS systems)

8 Substructure Testing Unified Approach Response Feedback ` Computational Substructure Physical Substructure Physical Substructure Structural Actuator Computational Substructure Shake Table Ground/Shake Table Shake table acceleration, ( ) A ctuator Force, F a = 1 α s m k u t = α 1 s u 1 3 s x 3 x 2 m 2 3 ( ) α ( ) ( ) First story contribution to shake table acceleration Third story contribution to shake table acceleration u + 1 α ( s) k ( x x ) First story contribution Third story contribution to actuator force to actuator force

9 α ( s) α ( s) = 0 and = Unified approach to substructure testing If α ( s) 0 and α ( s) 0, then the control requires a 1 3 shake table and an actuator to implement the substructure testing. If α ( s) = 0 and α ( s) = 0, then the controller require just 1 3 an actuator to implement the substructure testing as pseudo-dynamic dynamic testing: Note: in pseudo-dynamic dynamic testing, inertia effects are computed while in RTDHT are produced by shaking In dynamic hybrid testing ( α1( s) 0 or α3( s) 0 ), the actuator should operate in force control only

10 Real-time dynamic hybrid testing (RTDHT) Unique features Mass in the physical system Distributed inertia and rate-dependent effects Shake-table operated as acceleration device actuators in dynamic force control Sub-structuring force-based (interface forces applied to specimen) Dynamic test (has to be real-time) Challenges Dynamic force control Actuator/table structure interaction Numerical algorithms stability, error propagation Flexible harware/software architecture permitting different other types of tests (eg( eg: : pseudo dynamic test with shake-table as a displacement device)

11 Force control challenging problem Hydraulic actuator fitted with flow-regulating servo-valve valve Inherently a velocity source Designed to be mechanically stiff for good position control Friction, stick-slip, slip, breakaway forces on seals, backlash cause force noise Stiff oil columns make force control very sensitive to control parameters often leading to instability

12 Innovative scheme for force control using Series Elasticity Actuator Approach Target Force 1 / K LC Measured Force Command Signal Actuator in Displacement Control Series Spring, K LC Structure Compensator Structure Displacement

13 Small-scale test setup Series Spring Actuator Structure Disp. Transducer Load Cell Structure

14 Actuator displacement control Magnitude Tuned very well in displacement control Standard PIDF controller Frequency (Hz) Time-delay = 5.6 ms Phase (rad) Frequency (Hz)

15 Time-delay effect on force transfer function Magnitude Frequency (Hz) Experimental Analytical 5.6 ms delay Need predictive capability in compensator

16 Control scheme with Smith predictor compensator Smith Predictive Compensator 1/K LC + + Σ + Corrective Displcement + Σ Predictive Displcement T = e -sτ Actuator + - Σ K LC Series Spring Σ - + ˆT Delay Model 1 ms cs kˆ Kˆ 2 ˆ + ˆ + + LC Model of Structure- Spring System ms cs k Structure

17 Force transfer function with predictive compensation 2.0 Magnitude Frequency (Hz) Without comp. With comp.

18 Hybrid Controller Implementation (UB-NEES) Flexible architecture using parallel processing (see right side of diagram below) Delays of less than 5 milliseconds. Optional Optional Computationa l Substructure Physical Substructur Computationa l Substructure Physical Substructur Shake Table Structural Actuator MTS Actuator Controller (STS) MTS Hydraulic Power Controller (HPC) SCRAMNET I Compensation Controller xpc Target Network Simulator Real-time Simulator General Purpose Data Acquisition System Data Acquisition Ground/Shake Table MTS Shake Table Controller (469D) SCRAMNET II Hybrid Testing CONTROL OF LOADING SYSTEM HYBRID CONTROLLER UB-NEES NODE Design done jointly between MTS and UB

19 Pilot Test of Real Time Dynamic Hybrid Technique

20 Pilot Test of Real Time Dynamic Hybrid Technique

21 Implementation of RTDHT Actuator Structure Shake Table

22 Implementation of RTDHT From computational Substructure 1/K LC + Σ C + Compensation G Actuator Actuator + - Σ K LC Series Spring Actuator To computational Substructure Σ ms + cs+ k Experimental Subtructure dt dt Σ + - m3 u g Structure Shake Table Shake Table

23 Substructure response Actuator Structure Calculated Second floor Measured -Calculated Shake Table Calculated Measured First floor Hybrid test Analytical

24 Possible applications

25 Hybrid Testing of Electrical Systems Bushing Bushing Bushing Interface Reduced-Model Representation Bushing Interface Shake table Dynamically condensed model to simulate the transformer with bushing interface Transformer Ground Motion

models Achieved speeds of 100 milliseconds (based on UB-NEES developments) Computational Sites:

26 Fast-MOST FAST-PSEUDO PSEUDO-DYNAMIC-HYBRID 6-span bridge model FAST-PSEUDO PSEUDO-DYNAMIC-HYBRID - test in progress Span and one column are numerical models Other 4 columns are experimental models Achieved speeds of 100 milliseconds (based on UB-NEES developments) Computational Sites: UIUC/NCSA Slide courtesy of Gilberto Mosqueda Experimental Sites: Berkeley Boulder UIUC Buffalo Lehigh

27 Remarks Experimental Approaches Full scale (or large scale) testing of assemblies can be implemented only as substructure testing in the NEES Collaboratory Advanced analytical techniques require validation Hybrid testing may provide the framework for both of the above The current new technology allows for distributed hybrid dynamic testing although many issues need further solutions New experimentation and computing infrastructure in US and networking of such infrastructure allowed the advances necessary for such testing

28 Thank you! Questions?

REAL-TIME DYNAMIC HYBRID TESTING OF STRUCTURAL SYSTEMS

REAL-TIME DYNAMIC HYBRID TESTING OF STRUCTURAL SYSTEMS Andrei REINHORN Clifford C. Furnas Professor Mettupalayam V. SIVASELVAN and Zach LIANG Project Engineers, G. E. Brown Network for Earthq. Eng. Simulation