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Real-time Seismic Monitoring of the New Cape Girardeau
- MO) Bridge,” Earthquake Spectra, Volume 22, Issue 3
, 2006
"... This paper introduces the state-of-the-art seismic monitoring system ..."
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Cited by 9 (0 self)
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This paper introduces the state-of-the-art seismic monitoring system
Performance of several low-cost accelerometers
, 2014
"... erometers; example of Excel analysis sheet; table summaries of box-flip test results, sensor performance, and pricing infor-mation. ..."
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Cited by 6 (4 self)
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erometers; example of Excel analysis sheet; table summaries of box-flip test results, sensor performance, and pricing infor-mation.
Recorded Earthquake Responses from the Integrated Seismic Monitoring Network of the Atwood Building
, 2005
"... An integrated seismic monitoring system with a total of 53 channels of accelerometers is now operating in and at the nearby free-field site of the 20-story steel-framed Atwood Building in highly seismic Anchorage, Alaska. The building has a single-story basement and a reinforced concrete foundation ..."
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Cited by 5 (0 self)
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An integrated seismic monitoring system with a total of 53 channels of accelerometers is now operating in and at the nearby free-field site of the 20-story steel-framed Atwood Building in highly seismic Anchorage, Alaska. The building has a single-story basement and a reinforced concrete foundation without piles. The monitoring system comprises a 32-channel structural array and a 21-channel site array. Accelerometers are deployed on 10 levels of the building to assess translational, torsional, and rocking motions, interstory drift �displacement � between selected pairs of adjacent floors, and average drift between floors. The site array, located approximately a city block from the building, comprises seven triaxial accelerometers, one at the surface and six in boreholes ranging in depths from 15 to 200 feet ��5–60 meters�. The arrays have already recorded low-amplitude shaking responses of the building and the site caused by numerous earthquakes at distances ranging from tens to a couple of hundred kilometers. Data from an earthquake that occurred 186 km away traces the propagation of waves from the deepest borehole to the roof of the building in approximately 0.5 seconds. Fundamental structural frequencies �0.58 Hz �NS � and 0.47 Hz �EW��, low damping percentages �2–4%�, mode coupling, and beating effects are identified. The fundamental site frequency at approximately 1.5 Hz is close to the second modal frequencies �1.83 Hz NS and 1.43 EW � of the building, which may cause resonance of the building. Additional earthquakes prove repeatability of these characteristics; however, stronger shaking may alter these conclusions.
2004e, “Real-time Damage Prognosis of High-performance Fiber Reinforced Cementitious Composite Structures
- in Proceedings of Advances in Structural Engineering and Mechanics (ASEM’04), Seoul, Korea
"... High-performance fiber reinforced cementitious composites (HPFRCC) have the potential to provide civil structures with high ductility and damage tolerance. Low-cost wireless sensing networks are another emerging area that can monitor civil structures for signs of deterioration and damage. Developed ..."
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High-performance fiber reinforced cementitious composites (HPFRCC) have the potential to provide civil structures with high ductility and damage tolerance. Low-cost wireless sensing networks are another emerging area that can monitor civil structures for signs of deterioration and damage. Developed in isolation of one another, these two promising technologies can be integrated to provide HPFRCC structural elements capabilities to accurately monitor their performance to highly demanding loading conditions such as those posed by seismic events. In particular, the computational core of a wireless sensing unit can be harnessed to screen HPFRCC components for damage in real-time. A seismic damage index initially proposed for flexural dominated reinforced concrete elements is modified to serve as an algorithmic tool that can rapidly assess the extent of damage in shear-dominated HPFRCC elements. Embedded in the core of a wireless sensing unit prototype, the model is used to interrogate the deformation history of an HPFRCC coupling beam loaded cyclically in the laboratory.
Real-time structural monitoring and damage detection by acceleration and
- GPS sensors, 8th U. S. National Conference on Earthquake Engineering (April 2006 — http://www.1906eqconf.org/), submitted (15
, 2006
"... The objective in real-time structural monitoring is to track the changes in the dynamic characteristics of the structure and to detect and locate damage after an extreme event. Damage detection typically involves analysis of acceleration data to search for changes in the structure’s natural frequenc ..."
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The objective in real-time structural monitoring is to track the changes in the dynamic characteristics of the structure and to detect and locate damage after an extreme event. Damage detection typically involves analysis of acceleration data to search for changes in the structure’s natural frequencies. Data from instrumented structures have clearly shown that changes in natural frequencies are not always a reliable indicator of damage because various environmental factors can change frequencies without damage. Similarly, the inter-story drift, if calculated from acceleration records, is also not a reliable damage indicator because the errors generated by the noise in the records are exponentially amplified during the calculations. This paper presents new approaches to structural monitoring, damage detection, and data analysis. We propose that damage can be detected more accurately if we investigate, not only the changes in natural frequencies, but also the changes in the propagation characteristics of seismic waves in the structure and any permanent changes in the structure’s configuration. Since permanent deformations cannot be calculated accurately from acceleration data, we propose using GPS sensors. A 17-story, moment-resisting steel frame building at the UCLA campus in Los Angeles, California is currently being used to test these new concepts. The building is being monitored in real time with a very dense downhole-surface-structural array of accelerometers, plus three GPS sensors on the roof. We are developing adaptive signal processing and system identification tools to process and analyze the data in real time, and statistical decision-making tools to identify the changes in the building due to real damage from those due to environmental factors.
Data Compression of Structural Seismic Responses via Principled Independent Component Analysis
"... Abstract: This paper proposes a novel lossy data compression scheme for structural seismic responses based on principled (truncated) independent component analysis (PICA). It is first shown that independent component analysis (ICA) is able to transform a multivariate data set into a sparse represent ..."
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Abstract: This paper proposes a novel lossy data compression scheme for structural seismic responses based on principled (truncated) independent component analysis (PICA). It is first shown that independent component analysis (ICA) is able to transform a multivariate data set into a sparse representation space where is optimal for coding and compression, such that both the intradependencies and inter-dependencies (i.e., redundant information) between the multichannel data are removed for efficient data compression. Two examples are presented to demonstrate the compression performance of PICA, using the real-measured structural seismic responses from the 1994 Northridge earthquake, of the Fire Command Control (FCC) building and the USC hospital building, respectively. It is compared with the popular wavelet transform coding technique, which is only able to handle single-channel data separately. Results show that PICA achieves dramatically higher compression ratio (CR) than the wavelet method while retaining excellent reconstruction accuracy. It is also shown that PICA slightly outperforms the (principled) principal component analysis (PCA) method—which used to be considered optimal multivariate data compression scheme—with respect to both CR and reconstruction accuracy. Equipped with the FastICA algorithm that enjoys a cubic convergence rate, PICA has potential for rapid and reliable data transfer, communication (e.g., multihop wireless sensor network), storage, and retrieval in online or post-disaster (e.g., earthquake) monitoring and assessment applications of civil infrastructures. DOI: 10.1061/
Real-time monitoring of drift for occupancy resumption
- Proc. 14th World Conference on Earthquake Engineering (14WCEE
, 2008
"... At selected locations of instrumented structures, real-time displacements are acquired by either double integration of accelerometer time-series data, or differential GPS with high sampling ratios deployed at roofs of tall buildings. Thus, sensor data is related to performance level and health of a ..."
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At selected locations of instrumented structures, real-time displacements are acquired by either double integration of accelerometer time-series data, or differential GPS with high sampling ratios deployed at roofs of tall buildings. Thus, sensor data is related to performance level and health of a building. Drift ratios are computed as the parametric indicator of damage condition of a structure. Several levels of threshold drift ratios can be postulated in order to make decisions for inspections and/or occupancy. Drift ratio is computed using relative displacement between two floors computed from accelerometers strategically deployed at select number of pairs of consecutive floors. However, GPS-measured relative displacements are limited to being acquired only at the roof with respect to its reference base-yielding only average drift ratio for a building. Until recently, GPS systems available were limited to 10-20 samples per seconds (sps) capability – limiting their use only to long-period structures (T>1 s). Most recently, up to 50 sps differential GPS systems readily available are successfully used (Panagitou et al, 2006, Restrepo, pers. comm.. 2007) – thus enabling future usefulness of GPS to all types of structures. Experience with data acquired from both accelerometers and GPS deployments indicates that they are reliable and provide pragmatic alternatives to alert the owners and other authorized parties to make informed decisions and select choices for pre-defined actions following significant events. Furthermore, recent adoption of such methods by financial and industrial enterprises is testimony to their viability.
