Transcript Collaborative Research: Behavior of Braced Steel Frames
NEES@UCLA AS A RESOURCE FOR RAPID PROJECTS IN CHRISTCHURCH
Erica Eskes, Steve Keowen, Andrey Kozhukhovskiy, Robert Nigbor, Alberto Salamanca, Jon Stewart, John Wallace (NEES@UCLA) collaborating with: Geoff Chase, Stephanie Gutschmidt, Greg MacRae, Stefano Pampanin, Geoff Rodgers (University of Canterbury) Henri Gavin (Duke RAPID) Jose Restrepo, Matt Schoettler (UCSD RAPID)
ABSTRACT
NEES@UCLA provides equipment and personnel for the dynamic monitoring and testing of structures in the field. As we have done in previous earthquakes, we provided instrumentation, logistics, and staff to support two RAPID projects in Christchurch following the 2010 and 2011 earthquakes. The overall purpose of this effort was to obtain aftershock and ambient vibration data from several buildings. In July, 2011, an instrumentation system was mobilized to Christchurch and installed on two structures as part of the Restrepo et al. RAPID investigation of damaged RC buildings.
Aftershock monitoring continued through August, with dozens of aftershocks recorded in addition to large vibrations from demolition of nearby buildings in the Red Zone. In September the equipment was moved to a base isolated hospital building as part of the Gavin RAPID investigation of that building. Monitoring of aftershocks will continue through May 2012; to date more than 200 aftershocks have been recorded. Data from both RAPID efforts will be archived in the NEES Data Repository.
NEES@UCLA is part of NSF’s George E. Brown Jr. Network for Earthquake Engineering Simulation, with operation and maintenance funded by NSF under Award Number CMMI-0927178.
NEES@UCLA Resources for Dynamic Testing and Monitoring of Structures
Resources include:
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Shakers
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High resolution Instrumentation
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Field networking
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Mobile command truck
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CPT truck for characterization and subsurface sensors Force-balance accelerometers (75 uniaxial and 16 triaxial):
These accelerometers have a frequency range of DC to 200 Hz and wide dynamic range (155 dB , sub-micro-g to 4g).These sensors are suited for ambient and forced-vibration experiments and earthquake monitoring.
Other Sensors:
Other sensors include displacement, force, pressure, strain, temperature. Anything with an analog voltage output can be connected to the dataloggers. A string-pot displacement sensor is shown on the left.
2011-12 Christchurch Deployment
An 18-channel monitoring system was prepared and shipped to Christchurch in July 2011.
Equipment was shipped as baggage accompanying NEES@UCLA personnel.
Import/export formalities were handled via a Carnet.
The first two installations were for the Restrepo et al RAPID project. UC San Diego (UCSD) and University of Canterbury (UC) personnel had worked together to select the buildings (a 5 story carpark and a 9-story hotel in the Red Zone) and do the local planning and logistics. The • field measurements for this project were as follows: July 15: Install 6-channel triggered system in the Ibis Hotel. One XYZ accelerometer on the • roof, one in the basement.
July 16: Use 12-channel system to do complete ambient vibration measurements on the St.
George Hospital carpark, an RC structure had been damaged and was undergoing repairs.
Detailed ambient vibration data were recorded in several 20-minute sensor setups to provide overlapping spatial coverage of the building; these data can be used to get mode shapes and • modal parameters for the structure.
July 17-18: Triggered data were recorded for 2 days, resulting in the capture of several good • • • aftershock recordings.
July 18-19: Move 12-channel system to Ibis Hotel, do ambient vibration measurements.
July 19: Leave all 18-channels in final monitoring configuration, begin earthquake monitoring.
September 12: Remove equipment from Ibis Hotel, download data.
The third installation was for the Gavin RAPID project. Duke University and UC personnel had worked together to do local planning and logistics for the Christchurch Women’s Hospital (CWH), a new 5-story base-isolated building that had performed well in the earthquakes. UCLA augmented the 18-channel system from the previous deployments with a separate 3-channel • system, for 21-channels total. The field measurements for this project were as follows: September 15-16: Install three systems, one in CWH basement, one in CWH penthouse, and • one in the adjacent Parkside West (PSW) building.
September 16: Collect 1-hour of ambient vibration data • • September 17-present: hospital’s VPN.
Triggered earthquake recording, with remote access through the December 23: Significant aftershock swarm, with 2 M6, a few M5, and many M4 aftershocks.
Field Dataloggers (~150 channels):
Low power, rugged 24-bit A/D data loggers. The 6 and 12-channel units support real-time telemetry to a central site , wired or wireless. The dynamic range is approximately 135 dB RMS S/N, with GPS time stamp accuracy of <10 microsecond. Rockhound software is used to control and manage networks in the field, including real-time remote data viewing monitoring.
Ibis Hotel Building in Red Zone St. George Hospital Carpark SG Carpark Measurements Sample Ambient Vibration Data from Ibis Hotel Sample aftershock data
Portable eccentric mass shakers:
This is a smaller uni-directional eccentric mass shaker with a frequency range of 0-25Hz and a peak force of 20,000lb. It is “portable” in that it can be deployed by two people and carried in a pickup truck or shipped via air freight. Other larger shakers are available as well.
Christchurch Women’s Hospital PSW Sensor CWH basement sensors: acceleration and isolator displacement