Structural health monitoring using smart sensors

Structural control technology has been widely accepted as an effective means for the protection of structures against seismic hazards. Passive base isolation is one of the common structural control techniques used to enhance the performance of structures subjected to severe earthquake excitations. Isolation bearings employed at the base of a structure naturally increase its flexibility, but concurrently result in large base displacements. The combination of base isolation with active control, i.e., active base isolation, creates the possibility of achieving a balanced level of control performance, reducing both floor accelerations as well as base displacements. Many theoretical papers have been written by researchers regarding active base isolation, and a few experiments have been performed to verify these theories; however, challenges in appropriately scaling the structural system and modeling the complex nature of control-structure interaction have limited the applicability of these results. Moreover, most experiments only focus on the implementation of active base isolation under unidirectional excitations. Earthquakes are intrinsically multi-dimensional, resulting in out-of-plane responses, including torsional responses.Therefore, an active isolation system for buildings using multi-axial active control devices against multi-directional excitations must be considered.The focus of this dissertation is the development and experimental verification of active isolation strategies for multi-story buildings subjected to bi-directional earthquake loadings. First, a model building is designed to match the characteristics of a representative full-scale structure.The selected isolation bearings feature low friction and high vertical stiffness, providing stable behavior. In the context of the multi-dimensional response control, three, custom-manufactured actuators are employed to mitigate both in-plane and out-of-plane responses. To obtain a highiii fidelity model of the active isolation systems, a hybrid identification approach is used which combines the advantages of the lumped mass model and nonparametric methods. Controlstructure interaction (CSI) is also included in the identified model to further enhance the control authority. By employing the H 2 /LQG control algorithm, the controllers for the hydraulic actuators promise high performance and good robustness. The active isolation is found to possess the ability to reduce base displacements, as well as producing comparable accelerations over the passive isolation. The proposed active isolation strategies are validated experimentally for a sixstory building tested on the six degree-of-freedom shake table in the Smart Structures Technology Laboratory at the University of Illinois at Urbana-Champaign.iv ACKNOWLEDGMENTS

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“…However, the phase delays in the frequency domain can still be corrected through the method in Nagayama and Spencer (2007). …”

Section: Zeroed Controlmentioning

confidence: 99%

Multiaxial active isolation for seismic protection of buildings

Chang

Spencer

Shi

2013

Struct. Control Health Monit.

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“…Wireless sensor networks consist of a large number of spatially distributed devices known as smart sensors, which are characterized by computing and sensing capabilities. Wireless sensor networks are used for monitoring condition of structures, environmental influences, traffic, manufacturing and plant automation [1,2]. They consist of appropriately distributed and wirelessly enabled embedded devices in which a variety of electronic sensors can be used.…”

Section: Wireless Sensor Network -System Overviewmentioning

confidence: 99%

Bežični sustav mjerenja relativnih deformacija za ocjenu stanja infrastrukturnih građevina

Lakušić¹

2016

JCE

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Wireless sensors and sensor networks are emerging as substitutes for traditional structural monitoring systems. Their benefit lies in a lower cost of installation because extensive wiring is no longer required between sensors and the data acquisition system. Studies carried out to evaluate performance of wireless strain measurement units are described in this paper. An example is given of a wireless system used for measuring behaviour of a railway bridge, and comparison with traditional systems is made. Key words:Wireless sensor networks, strain, LabVIEW, wireless nodes, wireless gateways Stručni rad Arun Sundaram B., Ravisankar K., Senthil R., Parivallal S. Bežični sustav mjerenja relativnih deformacija za ocjenu stanja infrastrukturnih građevinaBežični senzori i senzorske mreže postaju zamjena za tradicionalne sustave za praćenje ponašanja konstrukcija. Njihova je prednost u nižoj cijeni ugradnje jer nema potrebe za polaganjem dugih kabela između senzora i sustava za prikupljanje podataka. U radu se opisuju istraživanja provedena u svrhu ocjenjivanja učinkovitosti bežičnih senzora za mjerenje relativnih deformacija. Dan je primjer primjene bežičnog senzorskog sustava pri mjerenju ponašanja konstrukcije željezničkog mosta te je napravljena usporedba s primjenom klasičnih sustava.

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“…The frequency of replacing batteries ranges within few weeks to few months depending on various factors such as the sampling frequency, the duration of each monitoring interval, and the on-sensor data postprocessing aiming for data compression [3][4][5][6][7][8] . The latter consideration reduces data transmission payloads in order to (i) prolong battery life, since wireless transmission is the most power consuming operation in a wireless sensor, and (ii) ensure the reliability of the monitoring system, since the amount of data that can be transmitted within a WSN is subjected to bandwidth limitations 3,4 .…”

Section: Introductionmentioning

confidence: 99%

“…The potential of using wireless sensor networks (WSNs) to facilitate field implementations for operational modal analysis (OMA) 1,2 of civil engineering structures has been widely recognized in the past two decades [3][4][5][6] . In particular, WSNs enable cable-free acquisition and transmission of response acceleration signals from linear vibrating structures excited by broadband ambient dynamic loads.…”

Section: Introductionmentioning

confidence: 99%

Assessment of sub-Nyquist deterministic and random data sampling techniques for operational modal analysis

Gkoktsi

Giaralis

2017

Structural Health Monitoring

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This article assesses numerically the potential of two different spectral estimation approaches supporting non-uniformin-time data sampling at sub-Nyquist average rates (i.e. below the Nyquist frequency) to reduce data transmission payloads in wireless sensor networks for operational modal analysis of civil engineering structures. This consideration relaxes transmission bandwidth constraints in wireless sensor networks and prolongs sensor battery life since wireless transmission is the most energy-hungry on-sensor operation. Both the approaches assume acquisition of sub-Nyquist structural response acceleration measurements and transmission to a base station without on-sensor processing. The response acceleration power spectral density matrix is estimated directly from the sub-Nyquist measurements, and structural mode shapes are extracted using the frequency-domain decomposition algorithm. The first approach relies on the compressive sensing theory to treat sub-Nyquist randomly sampled data assuming that the acceleration signals are sparse/compressible in the frequency domain (i.e. have a small number of Fourier coefficients with significant magnitude). The second approach is based on a power spectrum blind sampling technique considering periodic deterministic sub-Nyquist ''multi-coset'' sampling and treating the acceleration signals as wide-sense stationary stochastic processes without posing any sparsity conditions. The modal assurance criterion is adopted to quantify the quality of mode shapes derived by the two approaches at different sub-Nyquist compression rates using computer-generated signals of different sparsity and field-recorded stationary data pertaining to an overpass in Zurich, Switzerland. It is shown that for a given compression rate, the performance of the compressive sensing-based approach is detrimentally affected by signal sparsity, while the power spectrum blind sampling-based approach achieves modal assurance criterion .0.96 independently of signal sparsity for compression ratios as low as 22% the Nyquist rate. It is concluded that the power spectrum blind sampling-based approach reduces effectively data transmission requirements in wireless sensor networks for operational modal analysis, without being limited by signal sparsity and without requiring a priori assumptions or knowledge of signal sparsity.

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Structural health monitoring using smart sensors

Cited by 98 publications

References 17 publications

Multiaxial active isolation for seismic protection of buildings

Multiaxial active isolation for seismic protection of buildings

Bežični sustav mjerenja relativnih deformacija za ocjenu stanja infrastrukturnih građevina

Assessment of sub-Nyquist deterministic and random data sampling techniques for operational modal analysis

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