Large-Scale Real-Time Hybrid Simulation (RTHS) of Buildings

Transcription

1 Large-Scale Real-Time Hybrid Simulation (RTHS) of Buildings Chinmoy Kolay Assistant Professor Department of Civil Engineering Indian Institute of Technology Kanpur Kanpur, India Workshop on Performance Evaluation of Housing Units Noida, India July 21-22, 2017

2 Acknowledgements Doctoral Dissertation Advisor: Prof. James M. Ricles, Lehigh University, USA Fellowships: the RCEAS fellowship, Yen fellowship, and Gibson fellowship through the CEE Dept. Lehigh University Funding: Pennsylvania Infrastructure Technology Alliance; National Science Foundation Collaborators: Dr. Baiping Dong, Dr. Akbar Mahvashmohammadi, and Dr. Karim Kazemibidokhti ATLSS and NHERI staff: Thomas Marullo, Peter Bryan, Darrick Fritchman, Edward Tomlinson, Carl Bowman, Gary Novak Large-scale real-time hybrid simulations were conducted at the Real-Time Multi- Directional (RTMD) Experimental Facility at the Advanced Technology for Large Structural Systems (ATLSS) Center of Lehigh University, USA 2

3 Outline THE WHAT What is (real-time) hybrid simulation? THE WHY Why is (real-time) hybrid simulation important? THE HOW How is (real-time) hybrid simulation done? 3

4 Background: Dynamic Testing Shake table testing Most realistic method of dynamic testing of structures Limitations: Prototype scaled to accommodate shake table capacity Expensive Hybrid simulation (HS) and real-time hybrid simulation (RTHS) Viable alternative to shake table testing Effective force testing Force controlled test and requires all the mass to be present in the lab Limitations: Not economical Force control is more difficult than displacement control

5 What is (RT)HS? Hybrid method of testing combining experimental and analytical substructures Experimental substructure(s) Not well understood and modeled analytically Full scale component can be easily accommodated Rate dependent devices (e.g., dampers, base-isolators) can be tested Analytical substructure(s) Well understood and modeled numerically Various substructures possible for a given expt. substructure Damage can accumulate (not a problem) provided it can be modeled

6 Why is (RT)HS important? Cost effective large-scale testing method Integrates the benefit of computational and physical testing Comprehensive system and component response Meets the need of the earthquake engineering community 6

7 How is (RT)HS performed? Nonlinear damper Linear damper Ground acceleration a a X n+1, X n+1 Effective force F n+1 Integration of equations of motion a e M X n+1 + C X n+1 + R n+1 + R n+1 = F n+1 a R n+1 Simulation coordinator e R n+1 e X n+1 Nonlinear damper Linear damper Analytical substructure Experimental substructure Real time response 7

8 RTHS: Implementation issues and challenges Simulation coordinator Numerical integration algorithm Accurate Explicit Unconditionally stable Dissipative Fast communication Analytical substructure Fast and accurate state determination procedure for complex structures Preferred Experimental substructure Large capacity hydraulic system and dynamic actuators required Actuator kinematic compensation Robust control of dynamic actuators for large-scale structures

9 Velocity update: X n+1 = Kolay-Ricles-α (KR-α) Method X n + tα 1 X n Explicit Displacement update: Weighted equations of motion: X n+1 = X n + Δt X n + t 2 α 2 X n Numerical damping M I α 3 X n+1 + α 3 X n + C 1 α f X n+1 + α f X n + K 1 α f X n+1 + α f X n = 1 α f F n+1 + α f F n Unconditionally stable Numerical damping is controlled by ρ [1,0] ρ = 1 No numerical damping 0 Asymptotic annihilation Kolay, C., & Ricles, J. (2014). Earthquake Engineering & Structural Dynamics 9

10 RTHS of a Three-Story Steel Frame Building with Nonlinear Elastomeric Dampers 10

11 Motivation and Problem Statement In RTHS using explicit algorithms generally mass and initial stiffness proportional damping (PD) model is used Known to produce unrealistically large damping forces and inaccurate result when structure undergoes inelastic deformations Alternatively nonproportional damping (NPD) can be used Produces accurate results in nonlinear dynamic analysis using implicit algorithms Produces erroneous results in nonlinear dynamic analysis using explicit algorithms (e.g., CR) with a realistic time step size Member forces get contaminated with spurious participation of higher modes The problem is worsened by noise in the measured restoring forces in RTHS Numerical damping can be used to circumvent the problem 11

12 Prototype Building 3-story, 6-bay by 6-bay office building; seismic design category D MRFs designed to satisfy ASCE7 code strength requirement Story drift controlled by nonlinear elastomeric dampers installed in DBFs Test structures derived by scaling down the prototype by a factor of 0.6 West North South East Seismic tributary area for one MRF and DBF South North Refs.: Dong, Ph.D. dissertation, Lehigh University, 2015 Mahvashmohammadi, Ph.D. dissertation, Lehigh University,

13 RTHS Configuration West North South East Time discretized weighted equation of motion (KR-α Method): M X n+1 + C a X n+1 αf + (R n+1 αf e +R n+1 αf ) = F n+1 αf North 1987 Superstition Hills earthquake record scaled to DBE and MCE hazard levels Time step: Δt = 4 Lean-on-col. s MRF (gravity system 1024 & seismic mass) Analytical Substructure Experimental Substructure (DBF) 13

14 Analytical Substructure FE model developed in HybridFEM Columns and beams displacement-based nonlinear beam-column fiber elements and elastic beam-column elements MRF panel zone nonlinear panel-zone elements Nonproportional damping (NPD) model Gravity system lean-on-column using elastic elements with second order P Δ effects 247 DOFs and 74 elements Floor 3 Floor 2 Floor 1 Ground Level Basement North Rigid floor diaphragm (typ.) Panel zone element (typ.) Elastic element (typ.) Fiber element (typ.) RBS (typ.) Elastic element Fiber element MRF P 3 M 3 P 2 M 2 P 1 M 1 Lean-on col. (Gravity system & seismic mass) 14

15 MCE Level RTHS using ρ =

16 MCE Level RTHS using ρ = 0.75 Kolay et al. (2015). Earthquake Engineering & Structural Dynamics 16

17 MCE Level RTHS using ρ =

18 RTHS of a Two-Story RC Frame Building with Nonlinear Fluid Viscous Dampers 18

19 Motivation and Problem Statement Complex hysteretic behavior of a RC frame member is better modeled using a flexibility-based (FB) element FB element state determination requires an iterative procedure Not well suited for RTHS application Development of a new implementation scheme Limit the number of iterations to a fixed value Carry the unbalanced section forces to the next integration time step Influence of numerical damping on stability and accuracy Integration algorithm: MKR-α method (free parameter: ρ ) We will use ρ = ρ 2 as the free parameter 19

20 RTHS of a Two-Story Reinforced Concrete Building Prototype floor plan Earthquake record scaled to the MCE hazard level Time step: Δt = s Kolay, C., & Ricles, J. M. (2016). Journal of Structural Engineering (in press). 20

21 K D Damper Characterization u K C D, α u K, f K u C, f C Nonlinear Maxwell damper model u D, f D Model parameters identified using particle swarm optimization algorithm (PSO) K D = kn/m, C D = kn-(s/m) α α =

22 MCE Level Test Demonstration Kolay, C., & Ricles, J. M. (2016). Journal of Structural Engineering (in revision). 22

23 RTHS of a Tall Building with Damped Outriggers Under Wind Excitations (ongoing) 23

24 RTHS of a Wind Excited Tall Building (ongoing) 40-story (+4 basement) BRBF building in Los Angeles designed by SGH for TBI case studies Objectives Improve performance under wind loads using nonlinear fluid viscous dampers Assess performance using RTHS N-S E-W Plan for floors that do not include the outriggers. Image courtesy of Dutta and Hamburger (2010) Ref.: Moehle et al., PEER 2011/05 3-D view of the building. Image courtesy of Dutta and Hamburger (2010) 24

25 RTHS Configuration BRB: nonlinear truss element with Steel02 material (typical) Beams and columns: elastic beam-column element Nonlinear fluid viscous damper (typical): Modeled physically Wind load: Wind Tokyo Polytechnic University Wind Tunnel Test database Normalized pressure coefficient time histories are converted to full scale forces corresponding to Exposure B and wind speed of 110 mph Key features: P-Δ effects are included 780 Nodes 996 Elements 1590 DOFs 25

26 Demonstration of a typical test 26

27 Future IITK PDTF Development of HS and RTHS capabilities at IITK PDTF Development and performance evaluation of low cost housing Damage free structural system for seismic hazard mitigation (e.g., self-centering systems) (Ref: Sinha & Rai, 2009) RTHS using shake table and actuators RTHS of tall buildings under wind and seismic loads Advanced algorithms for HS and RTHS 27

28 Relevant Publications 1. Kolay, C. and Ricles, J. M. Assessment of explicit and semi-explicit classes of model-based algorithms for direct integration in structural dynamics. In: International Journal for Numerical Methods in Engineering (2016), pp doi: /nme Feng, D., Kolay, C., Ricles, J. M., and Li, J. Collapse simulation of reinforced concrete frame structures. In: The Structural Design of Tall and Special Buildings (2016), pp doi: /tal Kolay, C., Ricles, J. M., Marullo, T. M., Mahvashmohammadi, A., and Sause, R. Implementation and application of the unconditionally stable explicit parametrically dissipative KR-α method for real-time hybrid simulation. In: Earthquake Engineering and Structural Dynamics 44.5 (2015), pp doi: /eqe Kolay, C. and Ricles, J. M. Development of a family of unconditionally stable explicit direct integration algorithms with controllable numerical energy dissipation. In: Earthquake Engineering and Structural Dynamics 43.9 (2014), pp doi: /eqe Kolay, C. and Ricles, J. M. Improved explicit integration algorithms for structural dynamic analysis with unconditional stability and numerical dissipation. In: Journal of Earthquake Engineering (in press). 6. Kolay, C. and Ricles, J. M. Force-based frame element implementation for real-time hybrid simulation using explicit direct integration algorithms. Journal of Structural Engineering (in press). 28

29 Thank you 29