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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
GVDA-051906 2
GVDA-051906 3
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
GVDA-051906 22F4: Natural Earthquake
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.
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