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Advanced Technology for Large Structural Systems Center Lehigh University Yunbyeong Chae James M. Ricles Thomas M. Marullo Stephanie Tong ATLSS Center Lehigh University dampers Dampers Quake Summit 2012 July 9-12, 2012, Boston

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Advanced Technology for Large Structural Systems Center Lehigh University Objectives of Study Improving 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 processing

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Advanced Technology for Large Structural Systems Center Lehigh University Why Multi-Grid Real-Time Hybrid Simulation? photo from Maurer Sohne From www.worldofstock.com Fast computational demand can be resolved using multi-grid processing Difficult (size and $) to conduct shaking table tests for large-scale structural systems RTHS can be an effective tool to enable the investigation of dynamic response of large-scale structures with rate-dependent devices

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Advanced Technology for Large Structural Systems Center Lehigh University Case Study: 9-Story ASCE Benchmark Structure Ohtori et al. 2004, ASCE Journal of Engineering Mechanics, 130(4), 366-385

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Advanced Technology for Large Structural Systems Center Lehigh University Structural Design Performance Objective Limit 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 drift Limit 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 drift MCE ground motion: a 2% probability of exceedance in 50 years DBE ground motion: a 2/3rd intensity of the MCE

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Advanced Technology for Large Structural Systems Center Lehigh University Large-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

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Advanced Technology for Large Structural Systems Center Lehigh University Deployment of MR Dampers Performance Objective: to limit story drift to 1.5% under DBE How many MR dampers? Where to install dampers? Simplified Analysis Procedure Simplified Analysis Procedure

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Advanced Technology for Large Structural Systems Center Lehigh University Simplified Analysis Procedure Response prediction method for MDOF structure with MR dampers (Chae, Y., Ph.D. Dissertation, Lehigh University, 2011) Assume x 0 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 method Update x 0 using modal combination rules (SRSS, CQC, etc.) Check x 0 convergence Calculate damper force from the Hershel-Bulkley quasi-static MR damper model No Yes Perform response spectrum analysis with effective stiffness and equivalent damping ratio

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Advanced Technology for Large Structural Systems Center Lehigh University Deployment of MR dampers (based on Simplified Analysis Procedure, Chae 2011) 5 dampers 2 dampers 1 damper 10 dampers MR damper Number of MR dampers

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Advanced Technology for Large Structural Systems Center Lehigh University Schematic of Real-Time Hybrid Simulation Structure with MR dampers Analytical substructure + Experimental substructure(s) Actuators 1 st story MR damper 2 nd story MR damper

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Advanced Technology for Large Structural Systems Center Lehigh University Real-Time Hybrid Simulation

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Advanced Technology for Large Structural Systems Center Lehigh University Multi-Grid Real-Time Hybrid Simulation Ground motion Ground motion Update accelerations from equations of motion Update displacements/ velocities Experimental substructure restoring forces Integration algorithm Structural response + Analytical restoring forces xPC1 xPC1: Intel Core 2 Duo (2.66GHz CPU), 2GB RAM; runs at 512Hz (1/512sec) xPC2 xPC2: Intel Pentium 4 (2.4GHz CPU), 1GB RAM; runs at 102.4Hz (5/512sec) 2 xPCs used

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Advanced Technology for Large Structural Systems Center Lehigh University Analytical Substructure: 9-Story Building (using HybridFEM) Lean-on column Beams and columns are modeled using a distributed plasticity displacement-based beam-column element (nonlinear fiber element) Bi-linear material model Gravity frames modeled as a lean-on column with a geometric stiffness to account for P- effect Number of degrees-of- freedom: 508 Number of nonlinear fiber elements: 357

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Advanced Technology for Large Structural Systems Center Lehigh University Modeling of MR Dampers in Analytical Substructure -Maxwell 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 parameters Non-Newtonian fluid property is effectively accounted for by the nonlinear slider utilizing the Hershel-Bulkley visco-plasticity Suitable for a discretized frame work with moderate time steps

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Advanced Technology for Large Structural Systems Center Lehigh University Experimental Substructure - MR dampers in the 1 st and 2 nd stories - 2 nd story MR damper 1 st story MR damper 1700kN actuator Current driver Load cell 1700kN actuator

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Advanced Technology for Large Structural Systems Center Lehigh University Input Ground Motion 1994 Northridge earthquake recorded at Beverley Hills station (009 component) Scaled to DBE level with scale factor of 1.17 Unscaled ground motion

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Advanced Technology for Large Structural Systems Center Lehigh University Results of Multi-Grid RTHS Multi-grid RTHS Video

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Advanced Technology for Large Structural Systems Center Lehigh University Results of Multi-Grid RTHS Story drifts for 9-story building with MR dampers Performance objective (1.5% story drift)

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Advanced Technology for Large Structural Systems Center Lehigh University Without MR Dampers Story drifts for 9-story building without MR dampers 1.5% story drift 1 st story 2 nd story 3 rd story

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Advanced Technology for Large Structural Systems Center Lehigh University 9 th floor 5 th floor 3 rd floor 1 st floor Validation of Multi-Grid RTHS - Comparison of displacements between RTHS and numerical simulation -

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Advanced Technology for Large Structural Systems Center Lehigh University Comparison of Normalized TET Task Execution Time (TET): the amount of time needed to complete a single step during real-time hybrid simulation With Two xPCs xPC1 only xPC1xPC2 Maximum TET (TET max, sec)0.00090.00480.0016 Running time step (t, sec)1/512 (=0.0019)5/512 (=0.0098)1/512 (=0.0019)

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Advanced Technology for Large Structural Systems Center Lehigh University Summary and Conclusions Real-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 motions

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Advanced Technology for Large Structural Systems Center Lehigh University Acknowledgements This 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.

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Advanced Technology for Large Structural Systems Center Lehigh University Thank you