GVDA-0519061

NEES Field Facilities: NEES Field Facilities: A Resource for Earthquake A Resource for Earthquake Engineering (and Seismology) Engineering (and Seismology) Research and PracticeResearch and Practice

Bob NigborUCLA

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nees@ucsb

•3D Geotechnical Arrays at 2 permanent field sites in Southern California•Soil-Foundation-Structure-Interaction (SFSI) Test Structure

Real earthquake dataTest bed for geotechnical and geophysical methodsLocation for active experiments in a well-characterized field setting

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nees@ucla

•3 large mobile building shakers•Extensive field-deployable instrumentation system•CPT truck for research applications

Large-amplitude excitation of structuresField testing/monitoring of structures Site characterization and installation of subsurface sensors using CPT

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Large unidirectional shaker

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15kip Linear Shaker

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High Performance Mobile Network

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Mobile Command Center

Originally data acquisition trailer 8’ x 16’

Upgraded to self propelled vehicle 2003 Chevy Crew

cab 8’ x 15’ van body

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Wireless Network

Wire

less

Bac

kbon

e

Workgroup

Access points

Sensor stations

Data Concentrator

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Cone Penetration Testing (CPT) Truck

Vendor: Hogentogler, Inc.

Site characterization Tip resistance Sleeve resistance Inclination Pore pressure Geophone for shear

wave velocity

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Retrievable Subsurface Accelerometer

Insert with CPT truck Compatible with Q330

data loggers Retrievable with winch Silicon Designs MEMS

triaxial accelerometer Downhole signal

conditioning to reduce noise contamination

Micro-controller for built in sensor intelligence

Drive shoe

Probe

Triaxial accelerometer

Cable

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Q330

RSA Installation

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Shaker

RSAQ330

To Command

Center

Monitoring Concept

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Opportunities Experimental modal analysis of buildings &

other structures Nonlinear excitation of structures Verification of computer models of

structures Field verification of response modification

devices (active & passive control) Full-scale SFSI studies ????

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nees@ucsb

•3D Geotechnical Arrays at 2 permanent field sites in Southern California•Soil-Foundation-Structure-Interaction (SFSI) Test Structure

Real earthquake data for pure & applied researchTest bed for geotechnical and geophysical methodsLocation for active experiments in a well-characterized field setting

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Acknowledgements

Principal Investigators are: Les Youd, BYU Jamie Steidl, UCSB Bob Nigbor, USC

UCSB (led by Jamie Steidl) operates the two sites

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Location of Garner Valley Digital Array (GVDA) and Wildlife Array (WLA)

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GVDA Permanent Array

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GVDA Permanent Surface Array

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Upgraded Instrumentation

24-bit real-time dataloggers (Q330) On-site data concentrator computer

(Antelope ORB) High-speed wireless data

communications via HPWREN Concrete instrument building (instead

of trailer)

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SFSI Test Structure at GVDA

•4mx4mx4m•35 tons•Structural stiffness~soil stiffness•Configurable bracing to modify stiffness•Can add mass at roof•10 Hz fixed-base frequency without bracing, 15Hz with •Can bolt large shakers from UCLA to roof

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Native Soil

Water Table 0-3 m

Pore Pressure

Accelerometer

F1

F2

F3

5m

5m

F1 : Permanent Shaker

F2 : NEES@UCLA Shaker

F3 : NEES@UTexas Shaker

SFSI Structure Testing

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Measured Properties

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Uni-axial Accelerometer Tri-axial Accelerometer

Rotation Sensor Displacement Transducer

Pressure Cell and Sensor

Instrumentation

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SFSI Data System

•24-bit resolution•1000 sps/channel maximum•Real-time data output via TCP/IP•Multiple remote clients can observe and record data

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Potential Research Uses•Passive study of the effect of a structure upon ground shaking (What is “Free-Field”?). The existing GVDA array has recorded many small to moderate earthquakes, allowing detailed characterization of the site with no building. After addition of the 120-ton test building, it will be possible to study how the simple structure affects the earthquake ground motions at this simple site. Differences will be due to SFSI effects.

•Active study of liquefaction. Both the Wildlife and GVDA sites are on liquefiable soils, especially during the winter wet season. At both sites we will add concrete pads on which large shakers from the NEES University of Texas mobile shakers can be mounted. These shakers should be powerful enough to cause localized liquefaction. Data from such an experiment could then be used to verify predictive models of both liquefaction and ground shaking.

•Active study of SFSI physics. At GVDA, the reconfigurable test structure will have significant SFSI in the soft soil. The instrumentation can be used to measure structure and soil motion, soil pressures, and pore water pressures during active shaking of the structure by the UCLA NEES equipment. Such data will be invaluable for verification of predictive physics-based models of SFSI.