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Real-Time Hybrid Simulation Studies of Complex Large-Scale Systems Using Multi-Grid Processing Yunbyeong ChaeJames M. RiclesThomas M. MarulloStephanie Tong

ATLSS CenterLehigh University

dampersDampersQuake Summit 2012July 9-12, 2012, BostonAdvanced Technology for Large Structural Systems CenterLehigh University1Objectives of StudyImproving the speed of computational time in real-time hybrid simulation (RTHS) for investigation of dynamic response of large-scale structural systems

Implementing RTHS for a large complex structure using multi-grid processingAdvanced Technology for Large Structural Systems CenterLehigh University2Why Multi-Grid Real-Time Hybrid Simulation?

photo from Maurer SohneFrom www.worldofstock.comFast computational demand can be resolved using multi-grid processingDifficult (size and $) to conduct shaking table tests for large-scale structural systemsRTHS can be an effective tool to enable the investigation of dynamic response of large-scale structures with rate-dependent devices Advanced Technology for Large Structural Systems CenterLehigh University3Case Study: 9-Story ASCE Benchmark Structure

Ohtori et al. 2004, ASCE Journal of Engineering Mechanics, 130(4), 366-385Advanced Technology for Large Structural Systems CenterLehigh University4Structural Design Performance ObjectiveLimit story drift to 1.5% under the design basis earthquake (DBE) ground motion (satisfying the life safety performance level)

Use large-scale MR dampers to control the story driftMCE ground motion: a 2% probability of exceedance in 50 years DBE ground motion: a 2/3rd intensity of the MCE Advanced Technology for Large Structural Systems CenterLehigh University5Large-Scale Magneto-Rheological (MR) Damper by Lord Corporation Length = 1.47m (58in) Stroke = 297mm (12in) Weight = 280kg (615lb) Force capacity = 200kN at V=0.1m/sec, I=2.5A

Advanced Technology for Large Structural Systems CenterLehigh University6Deployment of MR DampersPerformance Objective: to limit story drift to 1.5% under DBEHow many MR dampers?Where to install dampers?

Simplified Analysis ProcedureAdvanced Technology for Large Structural Systems CenterLehigh University7Simplified Analysis ProcedureResponse prediction method for MDOF structure with MR dampers(Chae, Y., Ph.D. Dissertation, Lehigh University, 2011)Assume x0 and set

Determine maximum damper displacements

Calculate equivalent stiffness of MR dampers

Update effective stiffness of structural system

Update modal frequency and modal vector

Calculate representative loss factor of MR damper

Calculate equivalent damping ratio using lateral force energy methodUpdate x0 using modal combination rules (SRSS, CQC, etc.)Check x0 convergenceCalculate damper force from the Hershel-Bulkley quasi-static MR damper modelNoYesPerform response spectrum analysis with effective stiffness and equivalent damping ratio

Advanced Technology for Large Structural Systems CenterLehigh University8Deployment of MR dampers(based on Simplified Analysis Procedure, Chae 2011)

5 dampers5 dampers2 dampers2 dampers1 damper1 damper1 damper10 dampers10 dampersMR damperNumber of MR dampersAdvanced Technology for Large Structural Systems CenterLehigh University9Schematic of Real-Time Hybrid SimulationStructure with MR dampers

Analytical substructure

+Experimental substructure(s)Actuators1st story MR damper2nd story MR damperAdvanced Technology for Large Structural Systems CenterLehigh University10Real-Time Hybrid SimulationAdvanced Technology for Large Structural Systems CenterLehigh University11Multi-Grid Real-Time Hybrid SimulationGround motionUpdate accelerations from equations of motionUpdate displacements/ velocitiesExperimental substructure restoring forces IntegrationalgorithmStructuralresponse+Analytical restoring forcesxPC1xPC1: Intel Core 2 Duo (2.66GHz CPU), 2GB RAM; runs at 512Hz (1/512sec)xPC2xPC2: Intel Pentium 4 (2.4GHz CPU), 1GB RAM; runs at 102.4Hz (5/512sec)2 xPCs usedAdvanced Technology for Large Structural Systems CenterLehigh University12Analytical Substructure: 9-Story Building(using HybridFEM)

Lean-on columnBeams and columns are modeled using a distributed plasticity displacement-based beam-column element (nonlinear fiber element)Bi-linear material modelGravity frames modeled as a lean-on column with a geometric stiffness to account for P- effectNumber of degrees-of-freedom: 508Number of nonlinear fiber elements: 357Advanced Technology for Large Structural Systems CenterLehigh University13Modeling of MR Dampers in Analytical SubstructureMaxwell Nonlinear Slider (MNS) Model (Chae et al. 2012, EESD)

Pre- and post-yield behaviors are described independently by the Maxwell element and the nonlinear slider, respectively, making it easy to identify model parametersNon-Newtonian fluid property is effectively accounted for by the nonlinear slider utilizing the Hershel-Bulkley visco-plasticitySuitable for a discretized frame work with moderate time steps

Advanced Technology for Large Structural Systems CenterLehigh University14Experimental Substructure- MR dampers in the 1st and 2nd stories -

2nd story MR damper1st story MR damper1700kNactuatorCurrent driverLoad cellLoad cell1700kNactuatorAdvanced Technology for Large Structural Systems CenterLehigh University15Input Ground Motion

1994 Northridge earthquake recorded at Beverley Hills station (009 component)

Scaled to DBE level with scale factor of 1.17

Unscaled ground motionAdvanced Technology for Large Structural Systems CenterLehigh University16

Results of Multi-Grid RTHSMulti-grid RTHS VideoAdvanced Technology for Large Structural Systems CenterLehigh University17

Results of Multi-Grid RTHSStory drifts for 9-story building with MR dampersPerformance objective (1.5% story drift)Performance objective (1.5% story drift)Performance objective (1.5% story drift)Advanced Technology for Large Structural Systems CenterLehigh University18

Without MR DampersStory drifts for 9-story building without MR dampers1.5% story drift1.5% story drift1st story2nd story3rd storyAdvanced Technology for Large Structural Systems CenterLehigh University19

9th floor5th floor3rd floor1st floorValidation of Multi-Grid RTHS- Comparison of displacements between RTHS and numerical simulation -Advanced Technology for Large Structural Systems CenterLehigh University20Comparison of Normalized TET

Task Execution Time (TET): the amount of time needed to complete a single step during real-time hybrid simulationWith Two xPCsxPC1 onlyxPC1xPC2Maximum TET (TETmax, sec)0.00090.00480.0016Running time step (t, sec)1/512 (=0.0019)5/512 (=0.0098)1/512 (=0.0019)Advanced Technology for Large Structural Systems CenterLehigh University21Summary and ConclusionsReal-time hybrid simulation for a large-scale structure with large complexity has been conducted successfully using multi-grid processing procedure

The use of multiple xPCs enables the computations to be completed over a shorter duration, which may not be achieved with the conventional implementation of the RTHS method (i.e., using a single xPC)

Multi-grid real-time hybrid simulation enables the investigation of dynamic response of a large complex structural system under earthquake ground motionsAdvanced Technology for Large Structural Systems CenterLehigh University22AcknowledgementsThis study is based upon work supported by grants from the Pennsylvania Department of Community and Economic Development through the Pennsylvania Infrastructure Technology Alliance, and by the National Science Foundation under Award No. CMS-0402490 NEES Consortium Operation, and NEES REU Program. We would like to thank Lord Corporation and Professor Richard Christenson for their generous support of this research by providing the MR dampers.

Advanced Technology for Large Structural Systems CenterLehigh University23Thank youAdvanced Technology for Large Structural Systems CenterLehigh University24