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  Subjects -> ENERGY (Total: 300 journals)
    - ELECTRICAL ENERGY (2 journals)
    - ENERGY (181 journals)
    - ENERGY: GENERAL (8 journals)
    - NUCLEAR ENERGY (27 journals)
    - PETROLEUM AND GAS (54 journals)
    - RENEWABLE ENERGY (28 journals)

ENERGY (181 journals)                 | Last

Showing 1 - 200 of 406 Journals sorted alphabetically
ActaEnergetica     Open Access  
Advances in Building Energy Research     Hybrid Journal   (Followers: 9)
Advances in Energy and Power     Open Access   (Followers: 4)
Advances in High Energy Physics     Open Access   (Followers: 16)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 11)
American Journal of Energy Research     Open Access   (Followers: 8)
Annals of Nuclear Energy     Hybrid Journal   (Followers: 6)
Annual Reports on NMR Spectroscopy     Full-text available via subscription   (Followers: 2)
Annual Review of Resource Economics     Full-text available via subscription   (Followers: 10)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Solar Energy     Hybrid Journal   (Followers: 15)
Archives of Thermodynamics     Open Access   (Followers: 6)
Artificial Photosynthesis     Open Access   (Followers: 1)
Asian Bulletin of Energy Economics and Technology     Open Access   (Followers: 2)
Atomic Energy     Hybrid Journal   (Followers: 4)
Atoms for Peace: an International Journal     Hybrid Journal   (Followers: 4)
Batteries     Open Access   (Followers: 3)
Biofuel Research Journal     Open Access   (Followers: 3)
Biofuels     Hybrid Journal   (Followers: 10)
Biofuels Engineering     Open Access  
Biomass Conversion and Biorefinery     Partially Free   (Followers: 11)
Bulletin de droit nucleaire     Full-text available via subscription   (Followers: 1)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 34)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 19)
Carbon Management     Hybrid Journal   (Followers: 6)
Catalysis for Sustainable Energy     Open Access   (Followers: 5)
CERN courier. International journal of high energy physics     Free   (Followers: 6)
Chain Reaction     Full-text available via subscription   (Followers: 1)
Clefs CEA     Full-text available via subscription   (Followers: 1)
Computational Water, Energy, and Environmental Engineering     Open Access   (Followers: 4)
Dams and Reservoirs     Hybrid Journal   (Followers: 3)
Development of Energy Science     Open Access   (Followers: 4)
Distributed Generation & Alternative Energy Journal     Hybrid Journal   (Followers: 3)
E3S Web of Conferences     Open Access  
Economics and Policy of Energy and the Environment     Full-text available via subscription   (Followers: 7)
Electrical and Power Engineering Frontier     Open Access   (Followers: 18)
Electricity Journal     Partially Free   (Followers: 1)
ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations     Open Access   (Followers: 1)
Energy     Partially Free   (Followers: 23)
Energy & Fuels     Full-text available via subscription   (Followers: 23)
Energy and Buildings     Hybrid Journal   (Followers: 7)
Energy and Emission Control Technologies     Open Access   (Followers: 3)
Energy and Environment Focus     Free   (Followers: 6)
Energy and Environment Research     Open Access   (Followers: 11)
Energy and Environmental Engineering     Open Access   (Followers: 6)
Energy and Power     Open Access   (Followers: 8)
Energy and Power Engineering     Open Access   (Followers: 16)
Energy Conversion and Management     Hybrid Journal   (Followers: 7)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Harvesting and Systems : Materials, Mechanisms, Circuits and Storage     Hybrid Journal   (Followers: 2)
Energy Law Journal     Full-text available via subscription   (Followers: 4)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 18)
Energy Policy     Partially Free   (Followers: 55)
Energy Prices and Taxes     Full-text available via subscription   (Followers: 5)
Energy Procedia     Open Access   (Followers: 2)
Energy Reports     Open Access   (Followers: 3)
Energy Research & Social Science     Full-text available via subscription   (Followers: 1)
Energy Science & Engineering     Open Access   (Followers: 3)
Energy Science and Technology     Open Access   (Followers: 13)
Energy Strategy Reviews     Partially Free   (Followers: 9)
Energy Studies Review     Open Access   (Followers: 5)
Energy Systems     Hybrid Journal   (Followers: 12)
Energy Technology     Partially Free   (Followers: 4)
Energy Technology & Policy     Open Access   (Followers: 1)
Energy, Sustainability and Society     Open Access   (Followers: 17)
Environmental Progress & Sustainable Energy     Hybrid Journal   (Followers: 6)
EPJ Photovoltaics     Open Access   (Followers: 2)
Facta Universitatis, Series : Electronics and Energetics     Open Access  
Foundations and Trends® in Renewable Energy     Full-text available via subscription   (Followers: 1)
Frontiers in Energy     Hybrid Journal   (Followers: 3)
Frontiers in Energy Research     Open Access   (Followers: 2)
Fuel and Energy Abstracts     Full-text available via subscription   (Followers: 4)
Functional Materials Letters     Hybrid Journal   (Followers: 1)
Gcb Bioenergy     Open Access   (Followers: 2)
Geothermal Energy     Open Access   (Followers: 3)
Green     Hybrid Journal   (Followers: 2)
Green Energy & Environment     Open Access   (Followers: 1)
IEA Electricity Information     Full-text available via subscription   (Followers: 2)
IEA Natural Gas Information     Full-text available via subscription   (Followers: 2)
IEEE Power and Energy     Full-text available via subscription   (Followers: 23)
IEEE Transactions on Energy Conversion     Hybrid Journal   (Followers: 11)
IEEE Transactions on Nuclear Science     Hybrid Journal   (Followers: 8)
IEEE Transactions on Power Systems     Hybrid Journal   (Followers: 21)
IET Power Electronics     Hybrid Journal   (Followers: 22)
Ingeniería Energética     Open Access  
Innovations : Technology, Governance, Globalization     Hybrid Journal   (Followers: 5)
International Journal of Alternative Propulsion     Hybrid Journal   (Followers: 5)
International Journal of Ambient Energy     Hybrid Journal   (Followers: 1)
International Journal of Applied Power Engineering     Open Access   (Followers: 4)
International Journal of Clean Coal and Energy     Open Access   (Followers: 5)
International Journal of Coal Science & Technology     Open Access   (Followers: 1)
International Journal of Electric and Hybrid Vehicles     Hybrid Journal   (Followers: 8)
International Journal of Emerging Electric Power Systems     Hybrid Journal   (Followers: 4)
International Journal of Emerging Multidisciplinary Fluid Sciences     Full-text available via subscription   (Followers: 1)
International Journal of Energy and Environmental Engineering     Open Access   (Followers: 4)
International Journal of Energy and Power     Open Access   (Followers: 8)
International Journal of Energy and Statistics     Hybrid Journal  
International Journal of Energy Engineering     Open Access   (Followers: 9)
International Journal of Energy Research     Hybrid Journal   (Followers: 8)
International Journal of Energy Science     Open Access   (Followers: 1)
International Journal of Flow Control     Full-text available via subscription   (Followers: 4)
International Journal of Global Energy Issues     Hybrid Journal   (Followers: 7)
International Journal of Green Energy     Hybrid Journal   (Followers: 9)
International Journal of Hydrogen Energy     Partially Free   (Followers: 12)
International Journal of Marine Energy     Full-text available via subscription   (Followers: 1)
International Journal of Nuclear Desalination     Hybrid Journal  
International Journal of Nuclear Energy Science and Technology     Hybrid Journal   (Followers: 2)
International Journal of Nuclear Governance, Economy and Ecology     Hybrid Journal   (Followers: 1)
International Journal of Nuclear Hydrogen Production and Applications     Hybrid Journal   (Followers: 1)
International Journal of Nuclear Knowledge Management     Hybrid Journal   (Followers: 1)
International Journal of Power and Energy Conversion     Hybrid Journal   (Followers: 2)
International Journal of Smart Grid and Green Communications     Hybrid Journal  
International Journal of Sustainable Energy     Hybrid Journal   (Followers: 12)
International Journal of Sustainable Energy Planning and Management     Open Access   (Followers: 2)
International Journal of Sustainable Engineering     Hybrid Journal   (Followers: 7)
International Journal of Thermodynamics     Open Access   (Followers: 8)
Journal of Alternate Energy Sources & Technologies     Full-text available via subscription  
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 5)
Journal of China Coal Society     Open Access  
Journal of Energy     Open Access  
Journal of Energy & Natural Resources Law     Hybrid Journal   (Followers: 1)
Journal of Energy in Southern Africa     Open Access   (Followers: 2)
Journal of Energy Technologies and Policy     Open Access   (Followers: 5)
Journal of Energy, Environment & Carbon Credits     Full-text available via subscription   (Followers: 2)
Journal of Fusion Energy     Hybrid Journal   (Followers: 3)
Journal of International Energy Policy     Open Access   (Followers: 3)
Journal of Modern Power Systems and Clean Energy     Open Access   (Followers: 7)
Journal of Nano Energy and Power Research     Full-text available via subscription   (Followers: 4)
Journal of Nuclear Energy Science & Power Generation Technology     Hybrid Journal  
Journal of Ocean Engineering and Marine Energy     Hybrid Journal   (Followers: 1)
Journal of Physical Chemistry C     Full-text available via subscription   (Followers: 27)
Journal of Power Electronics & Power Systems     Full-text available via subscription   (Followers: 7)
Journal of Radiological Protection     Full-text available via subscription   (Followers: 4)
Journal of Renewable Energy     Open Access   (Followers: 4)
Journal of Semiconductors     Full-text available via subscription   (Followers: 2)
Journal of Solar Energy     Open Access   (Followers: 8)
Journal of Solar Energy Engineering     Full-text available via subscription   (Followers: 17)
Journal of Sustainable Bioenergy Systems     Full-text available via subscription   (Followers: 1)
Journal of Sustainable Energy Engineering     Full-text available via subscription  
Journal of Technology Innovations in Renewable Energy     Hybrid Journal   (Followers: 1)
Materials for Renewable and Sustainable Energy     Open Access   (Followers: 7)
MRS Energy & Sustainability - A Review Journal     Full-text available via subscription  
Natural Resources     Open Access   (Followers: 2)
Nature Energy     Hybrid Journal   (Followers: 3)
Nigerian Journal of Technological Research     Full-text available via subscription  
Nuclear Data Sheets     Full-text available via subscription  
Nuclear Engineering and Design     Hybrid Journal   (Followers: 10)
Nuclear Law Bulletin     Full-text available via subscription   (Followers: 2)
Nuclear Materials and Energy     Open Access   (Followers: 1)
Oil and Gas Journal     Full-text available via subscription   (Followers: 10)
Oil, Gas, Coal and Electricity - Quarterly Statistics - Electricite, charbon, gaz et petrole - Statistiques trimestrielles     Full-text available via subscription   (Followers: 8)
Open Journal of Energy Efficiency     Open Access   (Followers: 2)
Power Technology and Engineering     Hybrid Journal   (Followers: 3)
Proceedings of the Institution of Civil Engineers - Energy     Hybrid Journal   (Followers: 3)
Progress in Nuclear Energy     Hybrid Journal  
Radiochimica Acta     Hybrid Journal   (Followers: 5)
Radioprotection     Hybrid Journal   (Followers: 1)
Science and Technology of Nuclear Installations     Open Access   (Followers: 1)
Smart Grid and Renewable Energy     Open Access   (Followers: 8)
Solar Energy     Hybrid Journal   (Followers: 19)
Solar Energy Materials and Solar Cells     Hybrid Journal   (Followers: 27)
SourceOCDE Energie nucleaire     Full-text available via subscription  
SourceOECD Nuclear Energy     Full-text available via subscription   (Followers: 1)
South Pacific Journal of Natural and Applied Sciences     Hybrid Journal  
Strategic Planning for Energy and the Environment     Hybrid Journal   (Followers: 4)
Structural Control and Health Monitoring     Hybrid Journal   (Followers: 6)
Surface Science Reports     Full-text available via subscription   (Followers: 15)
Sustainable Energy     Open Access  
Sustainable Energy Technologies and Assessments     Full-text available via subscription  
Sustainable Energy, Grids and Networks     Hybrid Journal   (Followers: 1)
Technology Audit and Production Reserves     Open Access  
The International Journal of Ocean and Climate Systems     Full-text available via subscription   (Followers: 7)
The Journal of Computational Multiphase Flows     Full-text available via subscription  
Universal Journal of Applied Science     Open Access   (Followers: 2)
Washington and Lee Journal of Energy, Climate, and the Environment     Open Access   (Followers: 3)
Waste Management     Hybrid Journal   (Followers: 10)
Water International     Hybrid Journal   (Followers: 12)
Wiley Interdisciplinary Reviews : Energy and Environment     Hybrid Journal   (Followers: 4)
Wind Energy     Hybrid Journal   (Followers: 2)
Wind Engineering     Full-text available via subscription   (Followers: 2)
Wireless Power Transfer     Full-text available via subscription   (Followers: 3)

       | Last

Journal Cover Structural Control and Health Monitoring
  [SJR: 1.351]   [H-I: 26]   [6 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1545-2255 - ISSN (Online) 1545-2263
   Published by John Wiley and Sons Homepage  [1597 journals]
  • A state estimation method for wireless structural control systems
    • Authors: Z. Sun; G. Ou, S. J. Dyke, C. Lu
      Abstract: Structural control systems based on wireless sensors offer a convenient, flexible and cost‐effective alternative to their wired counterparts. Although wireless control systems (WCSs) have several attractive features, some challenges do remain related to the persistent presence of network‐induced time delays, and potential for sensor data losses and in extreme cases, sensor failures. The consequences of these challenges should be investigated, and solutions should be developed to achieve highly effective and robust control systems. The availability of such solutions will also encourage the adoption of WCSs in real structures. Here, an estimator switching method intended to minimize the influence of potential faults is developed and validated for WCSs. In this method, the switching gains are pre‐calculated to enable real‐time implementation. The proposed method is verified through numerical simulations of a seismically excited, three‐story structure considering various sensor data loss and sensor failure scenarios. The robustness of this estimation method in the presence of measurement noise and modeling uncertainty is also investigated. In addition, the estimation switching method is incorporated into a closed‐loop WCS in experiment. The results demonstrate the effectiveness of the proposed state estimation method in mitigating the impact of sensor data loss and sensor failure. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-15T23:00:43.49285-05:0
      DOI: 10.1002/stc.1929
       
  • Decentralised one‐class kernel classification‐based damage
           detection and localisation
    • Abstract: In this paper, a data‐based damage detection algorithm that uses a novel one‐class kernel classifier for detection and localisation of damage is presented. The demands of wireless sensing are carefully considered in the development of this fully decentralised and automated methodology. The one‐class kernel classifier proposed in this paper is trained through a faster and simpler to implement iterative procedure than other kernel classification methods, while retaining the same advantages over parametric methods, making it especially attractive for embedded damage detection. Acceleration time series at each sensor location are processed into autoregressive and continuous wavelet transform‐based damage‐sensitive features. Baseline values of these features are used to train the classifier, which can then classify features from new tests as damaged or undamaged, as well as outputting a localisation index, which can be used to identify the location of damage in the structure. This methodology is evaluated using acceleration data taken from a steel‐frame laboratory structure under various damage scenarios. A number of parametric studies are also conducted to investigate the effect of sampling frequency and baseline data sample size. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-15T22:45:36.566149-05:
      DOI: 10.1002/stc.1930
       
  • Blind modal identification of non‐classically damped structures under
           non‐stationary excitations
    • Authors: S. F. Ghahari; F. Abazarsa, E. Taciroglu
      Abstract: In the present paper, we extend a previously developed blind modal identification method to systems with non‐classical damping, which have complex‐valued mode shapes. Unlike conventional output‐only identification methods, blind modal identification method can provide modal property estimates when the input excitations are unknown and non‐stationary (e.g., for systems equipped with added dampers or soil–structure problems). In earlier work, we have developed a technique that can be used for non‐classically damped systems, but it is only applicable to stationary (i.e., ambient) excitations. Herein, we present an extension to non‐classically damped systems under non‐stationary (e.g., seismic) excitations. The proposed method yields mode shapes, natural frequencies and damping ratios, sequentially. A critical ingredient in this new method is a combination of generalized eigen‐decomposition and rough–fuzzy c‐means clustering techniques, which are employed to identify the complex‐valued mode shapes. The accuracy of the proposed method is verified through a simulated but realistic example. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-12T00:16:01.054272-05:
      DOI: 10.1002/stc.1925
       
  • High‐speed 6‐DOF structural displacement monitoring by fusing ViSP
           (Visually Servoed Paired structured light system) and IMU with extended
           Kalman filter
    • Abstract: In previous studies, a visually servoed paired structured light system (ViSP) was proposed to estimate structural displacement with high accuracy at low cost. Although the performance of the system has been verified from various simulations and experimental tests, it has a limitation that high‐speed dynamic displacement cannot be measured properly due to the relatively low sampling rate. To speed up ViSP, in this paper, an inertial measurement unit (IMU) with a high sampling rate is concurrently used with ViSP in a Kalman filtering framework. By combining measured accelerations and angular velocities from the IMU with the estimated 6‐DOF displacement from ViSP, high‐speed structural movement can be monitored with high accuracy. In the proposed data fusion method, named ViSP‐IMU, random biases of the IMU are calibrated by using the estimated displacement results from ViSP‐IMU. We perform experimental tests and verify the efficacy of the proposed algorithm as a promising structural displacement estimation method which guarantees high accuracy and a high sampling rate. Also, the proposed bias compensation method can effectively reduce the displacement estimation error by minimizing the difference between estimated displacements from the IMU and ViSP‐IMU. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-11T00:01:00.424014-05:
      DOI: 10.1002/stc.1926
       
  • Influence of tuning of passive TLD on the seismic vibration control of
           elevated water tanks under various tank‐full conditions
    • Authors: Anuja Roy; Aparna Dey Ghosh, Shyamal Chatterjee
      Abstract: This paper focuses on the seismic vibration control of elevated water tanks (EWTs) by the passive tuned liquid damper (TLD). Because of the fluctuating water content, the EWT is a variable‐mass system resulting in a continual modification of its natural frequencies. The problem of identifying the optimal tuning of the damper for robust performance over the range of fill depths of interest in the EWT is addressed here. The nonlinear model based on shallow water wave theory simulating sloshing motion of the liquid (here water) in the TLD is utilized. The sloshing of water in the EWT itself is considered by modeling the EWT as a two‐degree‐of‐freedom system, one representing the lateral vibrational mode of the supporting tank structure, tank container and impulsive mass of the water and the other denoting the fundamental sloshing mode of the water. A time domain study on a realistic reinforced concrete shaft supported EWT with TLD subjected to harmonic and recorded accelerogram input indicates that the TLD achieves significant response reduction and that it should be tuned to the structural frequency corresponding to the half‐full to three‐fourth full tank condition for robust performance. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-10T23:45:59.294632-05:
      DOI: 10.1002/stc.1924
       
  • Increasing the efficiency and efficacy of second‐order blind
           identification (SOBI) methods
    • Authors: P. T. Brewick; A. W. Smyth
      Abstract: This paper proposes a new technique to increase the efficiency and effectiveness of second‐order blind identification (SOBI) methods by reducing the number of time‐lagged covariance matrices required to produce highly accurate mixing matrix estimates. The technique is based on randomly selecting the time‐lagged covariance matrices as opposed to choosing them sequentially, which takes advantage of a property of independence with regard to the selection of time‐lagged covariance matrices, while simultaneously reducing the correlation between selected covariance matrices. The proposed randomized approach is first applied to undamped and damped sinusoids to demonstrate its effectiveness. The randomized method is then applied to a three‐degree‐of‐freedom linear structure subjected to random excitation. Finally, the proposed method is incorporated into a modified version of the SOBI method and applied to perform identification of the UCLA Factor building from recorded earthquake responses. In each case, the performance of the randomized approach is compared with the traditional sequential selection of time‐lagged covariance matrices, and the randomized approach consistently demonstrates superior performance both in terms of accuracy and efficiency. Additionally, the proposed randomized SOBI approach was easily inserted into the modified SOBI method demonstrating its malleability for SOBI variants and other blind source separation methods. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-10T23:20:42.056918-05:
      DOI: 10.1002/stc.1921
       
  • Study of wire rope devices for improving the re‐centering capability of
           base isolated buildings
    • Authors: Mariacristina Spizzuoco; Virginio Quaglini, Andrea Calabrese, Giorgio Serino, Claudia Zambrano
      Abstract: Wire rope devices have found numerous applications in the shock and vibration isolation of industrial machinery and equipment. The aim of the work is to present a preliminary investigation of their usefulness as a mean to increase the re‐centering capability of the isolation system of a civil structure. In the first part of the study, analytical formulations have been developed to predict the restoring stiffness of wire rope devices depending on their material and geometrical properties, and the direction of loading. In the second part, a preliminary assessment of wire rope springs has been performed based on unidirectional shake table tests on a scaled steel structure isolated with curved surface slider and either or not provided with wire rope springs. The changes in the seismic response of the isolation system are analyzed and some suggestions for improving the use of wire rope devices are drawn. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-10T00:46:30.603087-05:
      DOI: 10.1002/stc.1928
       
  • Monitoring of wind effects on an instrumented low‐rise building during
           the landfall of a severe tropical storm
    • Authors: Q.S. Li; Y.J. Wang, J.C. Li
      Abstract: Tropical cyclone‐induced disasters cause significant economic losses and heavy causalities every year. Most of the casualties were caused by low‐rise buildings collapsing. This study aims to investigate the characteristics of tropical cyclone‐generated winds and evaluate the wind effects on a typical low‐rise building under tropical cyclone conditions through field measurements. In‐situ monitoring was conducted on a full‐scale low‐rise building during the landfall of severe tropical storm Rumbia in 2013. Both the wind velocity field around and the surface pressures on the building were recorded during the storm. Characteristics of wind velocity field near ground during the windstorm were analyzed and compared with the specifications in the load code of China. Furthermore, when the wind approached in oblique directions, the windward roof corner suffered from the worst suctions under conical vortex. It was found that the maximum shape factors under the oblique winds were significantly larger than those specified in the load code. Moreover, probability density distributions of surface pressures induced by conical vortex were found to deviate from the Gaussian distribution. The outcomes of this study are expected to be of practical and imperative use to the wind‐resistant design of low‐rise buildings in tropical cyclone‐prone regions. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-03T23:56:34.786006-05:
      DOI: 10.1002/stc.1917
       
  • Acceleration‐based fault‐tolerant control design of offshore
           fixed wind turbines
    • Abstract: Wind turbines (WTs) are basically controlled by varying the generator load torque (with the so‐called torque control) and the blade pitch angles (with the so‐called pitch control) based on measurement of the generator shaft speed. These two controllers unitedly work to satisfy the control objectives, and it is crucial that they are tolerant to possible faults in the WT system. Passive fault‐tolerant control comprises the design of robust controllers against disturbances and uncertainties. This enables the controller to counteract the effect of a fault without requiring reconfiguration or fault detection. In this regard, the main contribution of this paper is to propose new control techniques that not only provide fault tolerance capabilities to the WT system but also improve the overall performance of the system in both fault‐free and faulty conditions. Coupling nonlinear aero‐hydro‐servo‐elastic simulations of an offshore WT with jacket platform is carried out for several pitch actuator faults. The jacket platform motions and structural loads caused by fault events with the proposed controllers are compared with loads encountered during normal operation and with respect to a well‐known baseline controller in the literature. The proposed controllers are based in the super‐twisting algorithm by using feedback of the generator shaft speed as well as the fore‐aft and side‐to‐side acceleration signals of the WT tower. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-02T01:57:27.07033-05:0
      DOI: 10.1002/stc.1920
       
  • Delamination detection in composite plates by synthesizing time‐reversed
           Lamb waves and a modified damage imaging algorithm based on RAPID
    • Authors: Zenghua Liu; Xuwen Zhong, Tuocan Dong, Cunfu He, Bin Wu
      Abstract: Combined with the modified damage imaging algorithm based on Reconstruction Algorithm for the Probabilistic Inspection of Damage (RAPID), a baseline‐free detection method of the Lamb waves based on time reversal method is developed to detect the delamination in the composite plate. Through the analysis of the focus position of time reversal signal, a new calculation method of Damage Index (DI) values is proposed. The modified damage imaging algorithm based on RAPID is integrated with two image fusion methods: full summation method and full multiplication method. According to the analysis of limitations of the modified damage imaging algorithm, the transducer array is adopted, and the problem of the uneven probability distribution caused by the uneven density of sensing network is discussed. Modified methods are proposed to eliminate the influence of the uneven probability distribution and improve the accuracy and reliability of the detection results. The parameter β significantly affects the effective detection range of each sensing path in the modified damage imaging algorithm. The value of parameter β was experimentally determined and reasonably applied to detect the delamination. Based on the calculation of the DI of individual sensing path and the imaging results of delamination, the identification and localization of delamination were experimentally achieved. The imaging results demonstrated the problem of the uneven probability distribution and the validity of modified methods. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-02T00:41:01.918994-05:
      DOI: 10.1002/stc.1919
       
  • Damage localization in a cable‐stayed bridge via bio‐inspired
           metaheuristic tools
    • Authors: Sara Casciati; Lorenzo Elia
      Abstract: Structural health monitoring is conceived to detect abnormal behaviors in structural systems. A highly non‐linear objective function built on the discrepancies between true and generated modal features can be minimized for this purpose. After a finite element discretization is built, the design variables are chosen, and the optimization problem solved. Two bio‐inspired metaheuristic tools, namely the artificial bee colony and the firefly algorithm, are employed to proceed toward the global minima. Comparing both identified and analytical stiffness matrices, the damage localization is performed. These methods are tested on a cable‐stayed bridge placed in northern Italy. The efficiency of these tools is compared. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-02T00:36:39.772215-05:
      DOI: 10.1002/stc.1922
       
  • Rolling bearing fault diagnosis under fluctuant conditions based on
           compressed sensing
    • Authors: Hang Yuan; Chen Lu
      Abstract: Bearings are widely used in industries and construction for shaft supporting or seismic isolation. In recent years, their fault diagnosis, especially under variable, or fluctuant conditions, has received increasing attention. Sufficient monitoring data are usually required for bearing diagnosis. However, sufficient data cannot be guaranteed in some engineering cases with limitations of the transmission channel bandwidth or onboard/onsite computational capabilities. Fortunately, the emerging compressed sensing technique, which provides an effective solution to data compression and processing, has the ability to transform traditional monitoring data to the compressed information domain for a highly effective diagnosis under fluctuant conditions. This study proposes a bearing fault diagnosis method under fluctuant conditions based on compressed sensing theory. First, a random matrix is constructed as the measurement matrix and is employed to compress the original signal into the compressed information domain. Then, reconstruction‐evaluation based fault diagnosis method is conducted with compressed signals. Moreover, the compressed signals used for fault diagnosis are reconstructed on the remote side. The experimental results provide evidence that the proposed method can effectively reduce the data volume required for bearing diagnosis and maintain an accuracy similar to current approaches, and the reconstructed signals can be used for other fault diagnosis methods. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-01T01:30:57.487242-05:
      DOI: 10.1002/stc.1918
       
  • Shake table investigation of a structure isolated by recycled rubber
           devices and magnetorheological dampers
    • Authors: Giuseppe Maddaloni; Nicola Caterino, Antonio Occhiuzzi
      Abstract: This paper describes the main results obtained from shaking table tests performed on a 1‐storey steel frame isolated by innovative rubber bearings and magnetorheological dampers (hybrid isolation). The proposed base isolation technology is based on the use of bearings made of a low‐cost recycled elastomer and reinforced with fibre sheets. Bounding the strain demand for such isolators because of severe earthquakes within acceptable values is a key point of this research, crucial for the effective application of this low‐cost technology to real cases. A specific semi‐active controller has been designed and adopted to achieve this goal. A set of natural earthquake records is applied to the base of the said structure using a shaking table system. The experimental results in terms of base displacement, roof acceleration and interstory drift are compared with the response of the same structure base isolated in the absence of magnetorheological dampers. It is found that when the semi‐active control is suitably designed and implemented, the seismic performance of the structure can be significantly improved. Even if referred to the case study, the conclusions encourage further investigating the application of the proposed low‐cost technology for seismic protection of buildings. © 2016 The
      Authors . Structural Control and Health Monitoring Published by John Wiley & Sons, Ltd.
      PubDate: 2016-07-26T23:55:35.761098-05:
      DOI: 10.1002/stc.1906
       
  • Relative vibration attenuation by means of self‐active devices
           constituted by permanent magnets separated by silicone layers
    • Authors: Enrico Ricciardi; Giovanni Ausanio, Vincenzo Iannotti, Vittorio Pasquino, Brigida Silvestri, Luciano Lanotte
      Abstract: The relative vibrations of two small frames with different stiffness, subjected to the same oscillating excitation coming from their base platform, were investigated. The effects of the innovative coupling of standard passive attenuation and time variation of magnetic forces (self‐produced by the vibration itself) were investigated. The first experimental tests demonstrate that the amplitude of relative vibration can be easily decreased up to 75% without requiring external energy. In perspective, by varying the attenuator shape and power, it is possible to use it in all the cases in which it is necessary to reduce the vibrations of a breakable or unstable structure inside a building accidentally exposed to vibration, such as a rotor inside a frame or a shelf in a museum room. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-26T03:50:37.736917-05:
      DOI: 10.1002/stc.1914
       
  • Guided wave propagation in H‐beam and probability‐based damage
           localization
    • Authors: Fucai Li; Hongguang Li, Jianxi Qiu, Guang Meng
      Abstract: H‐beams are usually made of structural steel and are widely used in construction, civil, and mechanical engineering. Both the rolling process and complex working condition can yield some defects on the H‐beam structures. Characteristics of guided wave propagation in H‐beam are investigated in this study for damage identification by using guided wave‐based structural health monitoring (SHM) technique. Wave structures are obtained for wave mode selection in H‐beam SHM applications. Guided waves are excited by using piezoelectric actuators. Two excitation ways, that is, symmetric excitation and circle excitation, are studied to select appropriate wave mode for damage identification. Based on the wave propagation characteristics, probability‐based diagnostic image method is proposed to estimate locations of simulated defects. In the image reconstruction process, arithmetic average‐based and geometric average‐based methods are investigated for damage localization with high precision. The results demonstrate that guided wave‐based SHM technique is applicable to damage identification for H‐beam structures. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-26T03:50:34.270892-05:
      DOI: 10.1002/stc.1916
       
  • Hybrid shake table testing method: Theory, implementation and application
           to midlevel isolation
    • Authors: Andreas H. Schellenberg; Tracy C. Becker, Stephen A. Mahin
      Abstract: A 2 m by 6 m unidirectional shake table was constructed at the University of California, Berkeley and combined with a real‐time hybrid simulation system creating a hybrid shake table. A series of tests were carried out to examine the viability of real‐time hybrid simulation techniques to perform experimental simulations of buildings with midlevel seismic isolation. The isolation system and superstructure were physically tested on the table while the portion of the building below the isolation plane was numerically modeled. OpenFresco was used to interface the numerical model with the control system. The isolated superstructure consisted of a two‐story steel moment frame on six triple friction pendulum bearings, which exhibit significant nonlinear velocity‐dependent behavior, necessitating real‐time testing. Shear building models with a range of periods were used to represent the portion of the building below the isolation plane. Increasing the number of degrees of freedom increased the control difficulty as higher modes were excited in the numerical model because of experimental errors caused predominantly by feedback noise and table tracking. Nonetheless, the results illustrate that hybrid shake table tests are indeed an economical and reasonably accurate method to assess the seismic behavior of midlevel isolation systems installed in a range of building configurations. Results showed that midlevel isolation was beneficial for the superstructure and, to a smaller extent, the substructure. However, to achieve maximum benefits, it is recommended that the effective period of the isolation system be sufficiently longer than the period of the substructure. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-22T04:10:49.221926-05:
      DOI: 10.1002/stc.1915
       
  • A new filter‐based pseudo‐negative‐stiffness control for
           base‐isolated buildings
    • Authors: Wei Gong; Shishu Xiong
      Abstract: A filter‐based pseudo‐negative‐stiffness (FPNS) control is proposed for seismic control of base‐isolated structures. The control algorithm is designed to produce a negative stiffness friction damping force with a gradual change at velocity switches, so that it is potential to prevent structures from experiencing significant jerks especially under earthquakes rich of high‐frequency components. The control algorithm requires information only on device's displacement. The effect of the control parameters on structural performance is studied and the optimal combination of control parameters is obtained with the consideration of control efficiency and the economy of control force. The superior performance of an active control system employing the FPNS control algorithm over that employing the conventional PNS control algorithm is verified. A semi‐active control design, MC‐FPNS, is developed to produce the control force of the FPNS control algorithm by MR dampers. The effectiveness and robustness of the MC‐FPNS control system are investigated through numerical analysis of the base‐isolated benchmark problem under earthquakes scaled to different intensity levels. The proposed MC‐FPNS control system is shown to be effective to not only prevent the isolator from failure but also improve the isolation functionality for a variety of earthquakes with different frequency contents and intensity levels. Moreover, the MC‐FPNS control system is capable of suppressing transference of high‐frequency components of ground motions to the superstructure. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-19T22:00:39.627815-05:
      DOI: 10.1002/stc.1912
       
  • Nonlinear imaging of damage in composite structures using sparse
           ultrasonic sensor arrays
    • Authors: F. Ciampa; Simon G. Pickering, Gennaro Scarselli, M. Meo
      Abstract: In different engineering fields, there is a strong demand for diagnostic methods able to provide detailed information on material defects. Low velocity impact damage can considerably degrade the integrity of structural components and, if not detected, can result in catastrophic failures. This paper presents a nonlinear structural health monitoring imaging method, based on nonlinear elastic wave spectroscopy, for the detection and localisation of nonlinear signatures on a damaged composite structure. The proposed technique relies on the bispectral analysis of ultrasonic waveforms originated by a harmonic excitation and it allows for the evaluation of second order material nonlinearities due to the presence of cracks and delaminations. This nonlinear imaging technique was combined with a radial basis function approach in order to achieve an effective visualisation of the damage over the panel using only a limited number of acquisition points. The robustness of bispectral analysis was experimentally demonstrated on a damaged carbon fibre reinforced plastic (CFRP) composite panel, and the nonlinear source's location was obtained with a high level of accuracy. Unlike other ultrasonic imaging methods for damage detection, this methodology does not require any baseline with the undamaged structure for the evaluation of the defect, nor a priori knowledge of the mechanical properties of the specimen. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-19T21:50:33.229032-05:
      DOI: 10.1002/stc.1911
       
  • Impact load identification for composite structures using Bayesian
           regularization and unscented Kalman filter
    • Abstract: In structural health monitoring of composite structures, one important task is to detect and identify the low‐velocity impact events, which may cause invisible internal damages. This paper presents a novel approach for simultaneously identifying the impact location and reconstructing the impact force time history acting on a composite structure using dynamic measurements recorded by a sensor network. The proposed approach consists of two parts: (1) an inner loop to reconstruct the impact force time history and (2) an outer loop to search for the impact location. In the inner loop, a newly developed inverse analysis method with Bayesian inference regularization is employed to solve the ill‐posed impact force reconstruction problem using a state‐space model. In the outer loop, a nonlinear unscented Kalman filter (UKF) method is used to recursively estimate the impact location by minimizing the error between the measurements and the predicted responses. The newly proposed impact load identification approach is illustrated by numerical examples performed on a composite plate. Results have demonstrated the effectiveness and applicability of the proposed approach to impact load identification. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-19T03:35:44.82534-05:0
      DOI: 10.1002/stc.1910
       
  • Semi‐active control of flexible structures using closed‐loop
           input shaping techniques
    • Authors: Tarek Edrees Alqado; George Nikolakopoulos, Leonidas Dritsas
      Abstract: In this research effort, a novel approach on the control of structures with magnetorheological (MR) dampers is presented, based on an appropriately adapted closed‐loop version of the generic input shaping control theory. The MR damper is a very promising kind of semi‐active control system (actuator), mixing the advantages of the active and passive structural control systems, hence their increasing use as attenuators that reject the effects of dynamic loads on civil engineering structures. The main contribution of this article is the application and performance evaluation of the novel ‘Linear Matrix Inequality‐based’ feedback version of the input shaping control theory for the first time in the area of structural control. The need for the use of a feedback version of input shaping control stems from the design trade‐off between robustness and speed of response requirements. A simulation of a benchmark three‐story building with one MR damper is employed to verify the efficiency of the proposed control approach. The nonlinear behaviour of the MR damper, rigidly connected between the first floor of the structure and the ground, is captured by the well‐known Bouc–Wen model. The superiority and effectiveness of the proposed scheme in reducing the responses of the structure were proved using seven quantifiable evaluation criteria and by comparing these results with those achieved by classical and well‐established alternative control schemes. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-11T02:58:18.261795-05:
      DOI: 10.1002/stc.1913
       
  • Polygonal damage shape reconstruction in plates using guided Lamb wave
    • Authors: Amir Ashkan Mokhtari; Abdolreza Ohadi, Hamidreza Amindavar
      Abstract: Tomographic reconstruction of the damaged region using guided Lamb waves provides important information about the health condition of structures. Two general types of shape reconstruction techniques are discussed before: transform based methods and algebraic iterative methods. There are some limitations associated with each method such as high sensitivity to noise and incomplete data sets, limitations for damage size and contrast, bulky setup for scanning the damaged region, or low speed of reconstruction. In this paper, the concepts of a novel method for reconstructing the contour of damage based on the Polygon Reconstruction Technique are introduced. First, the projections (Radon transform) of the damaged region are generated from a small number of angles with the aid of beamforming method. Then, the damaged region is modeled by a polygon, which its optimal number of vertices is estimated using the minimum description length (MDL) principle. Finally, using the polygon reconstruction technique, the coordinates of the vertices are determined. As the proposed method is at its preliminary stage, two finite element models of an aluminum plate with two different holes as the damage are designed in ABAQUS to examine the feasibility and performance of the method. Results show that the introduced technique based on polygonal damage shape reconstruction is fast and accurate. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-06T23:55:40.944939-05:
      DOI: 10.1002/stc.1907
       
  • Structural displacement measurements using DC coupled radar with active
           transponder
    • Authors: Shanyue Guan; Jennifer A. Rice, Changzhi Li, Yiran Li, Guochao Wang
      Abstract: Continuous wave (CW) radar sensors are a promising technology for structural displacement measurement. However, the commonly employed passive backscattering measurement configuration has some limitations for low‐power applications of CW radar. To improve displacement measurement performance using the low‐power CW radar, an active transponder configuration is introduced. Compared with passive backscattering, the active transponder configuration is capable of increasing the radar's signal power, thereby increasing the signal to noise ratio for more accurate displacement measurement. A series of laboratory experiments to demonstrate the performance of the transponder configuration was conducted, and the experimental results were compared with the results of using the backscattering configuration. The investigation revealed that the signal improvement provided by the transponder is a function of the distance between the transponder and the radar. In addition, a full‐scale bridge test with the active transponder configuration was conducted to verify the improved performance. An oblique angle test using the transponder was conducted in the laboratory to demonstrate the potential for flexible installation strategies when deploying the radar/transponder pair for bridge displacement measurements. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-06T02:46:07.386326-05:
      DOI: 10.1002/stc.1909
       
  • Estimation of wind loads on a tall building by an inverse method
    • Abstract: Many engineering applications require the knowledge of wind loads on structures. However, it is difficult or even impossible to measure these excitation forces from prototype structures directly. In this paper, a Kalman filtering‐based inverse approach is developed to estimate the wind loads on tall buildings. The inverse method allows estimating the wind forces on a tall building based on limited structural responses. The optimum solution of Kalman filter gain by solving the Riccati equation is used to update the wind load identification. The practicability and accuracy of the developed inverse method are evaluated based on wind tunnel testing results of a square‐shaped tall building. The wind loads identified by the developed method are compared with those by an augmented Kalman filtering‐based technique for further verification of the effectiveness and reliability of the presented inverse approach. The influences of key factors such as the type of wind‐induced response, covariance matrix of external loads, covariance matrix of noise, errors of structural modal parameters, and levels of noise involved in the measured responses on the wind load estimations are examined and discussed. It is shown through the comparative studies that the developed inverse method is an effective tool for estimating the wind loads on tall buildings based on limited structural responses. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-06T02:35:36.920985-05:
      DOI: 10.1002/stc.1908
       
  • Remaining stiffness estimation of buildings using incomplete measurements
    • Authors: Edward L. Eskew; Shinae Jang
      Abstract: After hazardous events, it is important to be able to quickly identify the remaining stiffness of affected structures for condition evaluation. Model updating can be used to update structural models to reflect current conditions based upon experimental measurements. Direct model updating is a simple and quick method of damage detection, but does not guarantee physical relevance. Least‐squares optimization can be used to accurately identify damage with physical relevance, but needs more measurements then updating parameters in order to produce an accurate solution. However, after an extreme event sensors on the structure may be damaged, creating a scenario with limited measurements which can render optimization techniques incapable of assessing the remaining stiffness. To address this issue, this paper proposes a two‐phase method to localize and then quantify the remaining stiffness of the structure. Direct model updating with limited measurements is used to localize potential damage to a subset of parameters, and a least‐squares optimization using the localized parameters is used to quantify the remaining stiffness in the structure. Numerical simulations using a simplified model based upon the phase I IASCE‐ASCE structural health monitoring benchmark problem with missing first floor sensors have been employed to demonstrate, and experiments using a five‐story steel frame structure are conducted to validate the methodology. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-06T02:30:36.939442-05:
      DOI: 10.1002/stc.1899
       
  • Full‐field deformation measurements during seismic loading of
           masonry buildings
    • Authors: S. Rajaram; P. A. Vanniamparambil, F. Khan, M. Bolhassani, A. Koutras, I. Bartoli, F. Moon, A. Hamid, P. Benson Shing, J. Tyson, A. Kontsos
      Abstract: This article demonstrates the potential of the digital image correlation (DIC) method to provide accurate full‐field deformation measurements and successfully monitor the development of damage during seismic excitation of a partially grouted reinforced masonry building. The building was subjected to a sequence of earthquake ground motion records using the Large High Performance Outdoor Shake Table at the University of California, San Diego. The DIC setup was capable of measuring surface deformations of the single‐story building with high frame rate cameras located at a distance greater than 50 ft away. The accuracy of the measurements was assessed with data obtained using mounted displacement transducers. The full‐field deformation data collected by the DIC system was capable to detect strain localization patterns associated with the onset of wall cracking before it could be shown by the displacement sensor data or by post mortem visual inspection. The research findings reported herein demonstrate, for the first time to the authors' best knowledge, the potential of in situ monitoring of actual structures for damage induced by non‐stationary loading profiles using optical metrology. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-04T03:11:52.604838-05:
      DOI: 10.1002/stc.1903
       
  • Experimental damage evaluation of open and fatigue cracks of
           multi‐cracked beams by using wavelet transform of static response via
           image analysis
    • Authors: Ugo Andreaus; Paolo Baragatti, Paolo Casini, Daniela Iacoviello
      Abstract: In this study, a method for crack detection and quantification in beams based on wavelet analysis is presented. The static deflection is measured at particular points along the length of (i) real damaged structures, using few displacement transducers and a laser sensor, and (ii) simulated structures, using closed‐form analysis, for a given location of a concentrated load along the beam. Furthermore, the measurement of the beam displacements in a large number of spatially distributed points is made by processing digital photographs of the beam. The smoothed deflection responses of the cracked beams are then analyzed using the wavelet transform. For this purpose, a Gaus2 wavelet with two vanishing moments is utilized. The wavelet transform spikes are used as indicators to locate and quantify the damage; furthermore, the multi‐scale theory of wavelet is employed, in order to eliminate or at least reduce the spurious peaks and enhance the true ones. Simply supported beams with single and double cracks are used to demonstrate the devised methodology. Open and fatigue cracks of different sizes and locations have been used in the examples. In a closed‐form analysis, the damage is modeled as a bilinear rotational spring with reduced stiffness in the neighborhood of the crack location. Damage calibration of simply supported steel beams with open and fatigue cracks has been carried out experimentally using this technique. A generalized curve has been proposed to quantify the damage in a simply supported beam. Based on the experimental study, the spatial wavelet transform is proven to be effective to identify the damage zone even when the crack depth is around 3% of the height of the beam. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-29T03:20:31.139805-05:
      DOI: 10.1002/stc.1902
       
  • Damage evaluation of structures with uncertain parameters via interval
           analysis and FE model updating methods
    • Authors: Enrique Sevillano; Rui Sun, Ricardo Perera
      Abstract: Experimental and numerical uncertainties are always present in structural identification problems. The quantification of the uncertainty on the results of a finite element updating procedure is commonly carried out in a probabilistic framework, which requires working with a‐priori known probability distributions for the uncertain parameters. In this paper, the modal interval analysis method to estimate damage structural problems with uncertain‐but‐bounded parameters is presented. With this method only the bounds on the magnitude of uncertain parameters are required. The formulation of this method in a single objective framework is equivalent to minimizing the average value and the deviation of the uncertain objective function in the considered interval with which it is actually a multi‐objective problem. Furthermore, its implementation requires the analytical evaluation of the sensitivities of the objective functions with respect to the uncertain parameters, which is derived. Numerical and experimental results evidence the accuracy and the effectiveness of the proposed approach to evaluate damage in uncertain environments. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-29T03:10:49.358053-05:
      DOI: 10.1002/stc.1901
       
  • Field monitoring and numerical simulation of the thermal actions of a
           supertall structure
    • Abstract: Structural temperature is an important loading that must be considered during the design, construction, and safety assessment. The thermal action of supertall structures has rarely been investigated because of insufficient real measurement data, as compared with that on bridges. In this study, the thermal action of the 600‐m‐tall Canton Tower is investigated on the basis of the comprehensive long‐term SHM system installed on the structure and the numerical simulation. First, the temperature model of the entire structure is derived by using the field monitoring and numerical heat transfer analysis data. In particular, (i) the temperature difference between different facades of the inner tube, (ii) the temperature difference profile of the outer tube, and (iii) the distribution of the temperature difference between the inner and outer tubes along the structural height are presented in detail. Results show that the nonuniform distribution of the temperature field between the different components of the structure is significant and should be carefully considered in the analysis of such a complex supertall structure. Second, the temperature effects on structural displacement, stress, and internal forces consisting of (i) the tower top horizontal displacement during different seasons, (ii) the stresses of different levels/components, and (iii) the bending moments/shear forces along the structural height are investigated. The simulated results obtained by using the global finite element model of the tower are verified through a comparison with the measurements. This study provides first‐hand data for the design of supertall structures in the tropical region of China. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-23T00:06:16.376685-05:
      DOI: 10.1002/stc.1900
       
  • Experimental study and numerical simulation on a new type of viscoelastic
           damper with strong nonlinear characteristics
    • Authors: Shunming Gong; Ying Zhou
      Abstract: In this study, a new type of viscoelastic (VE) damper with strong nonlinear characteristics, showing both softening and hardening, is investigated. Firstly, its performance tests are executed, and its mechanical properties summarized. Then, a shaking table test on a three‐story viscoelastically damped structure is designed to investigate the dissipation characteristics and control effect of this type of VE damper. Six VE dampers were installed in pairs at each story and connected vertically to the upper and lower beams. The structure with additional VE dampers and that without additional VE dampers was subjected to three ground motions whose peak ground accelerations varied from 0.1 to 0.6 g. The experimental results indicate that the control effect on the displacements was remarkable, while the effect on accelerations and shear forces was limited, due to the damper's additional stiffness. With the increment of the damper deformation, the additional stiffness decreased, while the additional effective damping ratio increased at first and then declined. Finally, a simplified analytical method is proposed and applied to simulate the shaking table test using OpenSees. The simulating results validate the analytical method of this type of VE damper. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-21T01:26:08.636177-05:
      DOI: 10.1002/stc.1897
       
  • An innovative sensitivity‐based method for structural model updating
           using incomplete modal data
    • Authors: Akbar Esfandiari
      Abstract: This paper presents an innovative sensitivity equation to detect changes of stiffness parameters using mode shape data. Most of the sensitivity‐based model updating methods use changes of mode shapes for structural model updating. However, the proposed method uses the mode shape data to estimate changes of the structural parameters directly. The proposed method sets up a relation between the change of structural parameters and the mode shapes of the damaged structure. The proposed formula uses the measured natural frequencies of the damaged structure and the mode shapes of the intact structure. The formulation yields to a set of accurate sensitivity equations. The proposed method is successfully applied to a plane truss and a frame structure using simulated error‐contaminated mode shapes data. Results prove robustness of the proposed method against mode shape, natural frequency, and mass modeling errors. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-21T01:21:55.316413-05:
      DOI: 10.1002/stc.1905
       
  • Transducer placement optimisation scheme for a delay and sum damage
           detection algorithm
    • Authors: M. S. Salmanpour; Z. Sharif Khodaei, M. H. Aliabadi
      Abstract: In this work, a transducer placement scheme based on wave propagation is proposed, which enhances damage localisation. The method was tailored to seek an optimal transducer network placement for a delay and sum damage detection algorithm. The proposed method determines a coverage index map and utilises a genetic algorithm to determine an optimal transducer network. It can also minimise the impact of faulty transducers, incorporate the effect of stiffeners and different damage types. The method is initially verified using numerically simulated signals. The optimal network outperformed the suboptimal for detection of holes and debonding in a stiffened panel. It is also shown that the coverage index reflected the localisation accuracy. The method is then validated with experimental results and the generated optimal transducer network compared with a suboptimal arrangement. The optimal network is shown to locate an actual crack with significantly higher accuracy than the suboptimal arrangement. © 2016 The
      Authors . Structural Control and Health Monitoring published by John Wiley & Sons, Ltd.
      PubDate: 2016-06-21T01:21:35.761321-05:
      DOI: 10.1002/stc.1898
       
  • Dynamic displacements‐based model updating with motion capture
           system
    • Authors: Byung Kwan Oh; Jin Woo Hwang, Se Woon Choi, Yousok Kim, Tongjun Cho, Hyo Seon Park
      Abstract: In this paper, a dynamic displacements‐based model updating method using a motion capture system (MCS) is proposed. The dynamic characteristics from MCS are used to find the parameters that minimize the difference between updated model and direct measurement. Using a multi‐objective optimization algorithm of non‐dominated sorting genetic algorithm‐II, the number of objective functions for model updating is set to the same number of modes under consideration, and all the objective function are simultaneously minimized. To consider the contribution of each mode on model updating and to avoid biased results, a rule for weighting of solutions associated to each mode based on modal participation factors is suggested and tested. Using a free vibration experimental test of a three‐story shear model, the performance of model updating method is verified by the comparison of the dynamics characteristics between the updated model and direct measurement by MCS. In addition, time histories of displacements from the updated model are compared with the direct measurement. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-21T01:00:44.257955-05:
      DOI: 10.1002/stc.1904
       
  • A baseline‐free and non‐contact method for detection and imaging of
           structural damage using 3D laser vibrometry
    • Authors: P. Aryan; A. Kotousov, C. T. Ng, B. S. Cazzolato
      Abstract: Detection and characterisation of structural damage using guided waves is very promising technique in non‐destructive testing and structural health monitoring systems. Because of their simplicity and low cost, current techniques normally utilise traditional piezo‐electric or optical fibre sensors to capture a directional scattered field from a defect or damaged area. However, the practical implementation of these techniques usually requires an extensive preliminary study in order to identify a suitable location and polarisation of the sensors, as well as determine the optimal parameters for wave excitation, which vary depending on the size and type of damage and structure. Recent advances in 3D laser vibrometry provide an opportunity to avoid many of the restrictions and limitations associated with traditional (1D) sensing systems by capturing the transient 3D displacement/velocity fields rather than the displacement/strain along a single axis and limited to a small number of discrete locations. Using 3D laser vibrometry, this paper suggests a non‐contact, baseline‐free method for imaging structural defects such as corrosion spots, cracks and dents as well as delamination damage. It focuses on the mode conversion effects and investigates the sensitivity of the in‐plane and out‐of‐plane scattered fields in relation to the presence of common defects. The experimental measurements are presented in terms of the root mean square (RMS) values of the velocity field. The outcomes of the present study can help in a number of ways, including selecting an appropriate strategy for defect detection using guided wave techniques. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-10T03:22:06.282057-05:
      DOI: 10.1002/stc.1894
       
  • Damage detection of multi‐story shear buildings due to earthquakes
           by model updating method
    • Authors: J.Y. Zhang; T. Aoki
      Abstract: In this paper, we present a novel model updating method for damage detection of multi‐story shear buildings during severe earthquakes. The story stiffnesses are explicitly presented in an incremental manner; this enables a simple and robust algorithm for the purpose of identification of the story stiffnesses. The estimated modal data, including natural frequencies and mode shapes of lower modes, are used in the proposed algorithm; moreover, sensitivity analysis of natural circular frequencies is incorporated to reduce possible errors. The story stiffnesses are identified by an iterative algorithm, and the window shift technique is adopted to present change of the story stiffness due to damages in the buildings during earthquakes. Numerical examples demonstrate that the proposed method is of high accuracy, even when the recorded responses are polluted by a relatively high level of (white) noises. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-10T03:15:36.476483-05:
      DOI: 10.1002/stc.1895
       
  • A leverage‐type stiffness controllable mass damper for vibration
           mitigation of structures
    • Abstract: Tuned mass dampers (TMDs) are well recognized as an effective technology for mitigating structural vibration caused by wind loads. Therefore, some researchers have advocated applying TMDs for the vibration mitigation of structures subjected to earthquakes. Nevertheless, the seismic performance of a conventional TMD may not be as effective as expected because the frequency content and magnitude of an earthquake usually fluctuate and are far more complex than wind loads. To resolve this problem, the leverage‐type stiffness controllable mass damper (LSCMD), a semi‐active mass damper, is proposed in this paper. The LSCMD has a lever arm with a movable pivot, allowing it to control the damper stiffness and restoring force in real time by adjusting the pivot position. To evaluate the control effectiveness of the LSCMD, the seismic responses of a structural system equipped with the LSCMD were simulated and compared with those of the same structure controlled by two optimally designed passive TMDs and a hybrid mass damper (HMD) with the same control law as that of the LSCMD. The results of the simulation demonstrate that the control performance of the LSCMD system can be enhanced by varying the LSCMD stiffness. Although the LSCMD and HMD are equally effective in suppressing the maximum responses of the structure, the former requires less control energy. This indicates that the proposed LSCMD is more desirable when the damper installation space and energy consumption are major concerns. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-10T03:11:54.501524-05:
      DOI: 10.1002/stc.1896
       
  • Semiactive control for a distributed mass damper system
    • Authors: Tat S. Fu; Erik A. Johnson
      Abstract: Recently, a distributed mass damper (DMD) has been proposed for architectural design considerations. By placing a mass damper in every story of a building, building designers can (1) integrate shading fins (that are typically installed in every story) and mass dampers to synergistically improve safety and energy efficiency, and (2) solve many architectural design and implementation issues (e.g., complications of a large damper mass near the top or the prime space of a building) with small damper masses. The passive DMD system was shown effective in response mitigation as a conventional tuned mass damper. In this paper, two semiactive DMD strategies are evaluated: a conventional semiactive clipped‐optimal LQR strategy, and a proposed gain‐scheduled semiactive DMD strategy. A conventional clipped‐optimal approach turns individual dampers off when their control forces are nondissipative, whereas the proposed strategy uses a redesigned control force, using an alternate control gain, to maximize the number of dampers exerting dissipative forces. A five‐story shear structure with one semiactive tuned mass damper per floor is used as a testbed to evaluate these control strategies. Both semiactive DMD strategies best the passive DMD system in reducing structural response; further, the semiactive gain‐scheduling strategy notably outperforms the established clipped‐optimal semiactive control strategy. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-10T03:05:35.634683-05:
      DOI: 10.1002/stc.1888
       
  • Compressive sensing based structural damage detection and localization
           using theoretical and metaheuristic statistics
    • Authors: Ruigen Yao; Shamim N. Pakzad, Parvathinathan Venkitasubramaniam
      Abstract: Accurate structural damage identification calls for dense sensor networks, which are becoming more feasible as the price of electronic sensing systems reduces. To transmit and process data from all nodes of a dense network is a computationally expensive BIG DATA problem; therefore scalable algorithms are needed so that inferences about the current state of the structure can be made efficiently. In this paper, an iterative spatial compressive sensing scheme for damage existence identification and localization is proposed and investigated. At each iteration, damage existence is identified from randomly collected sparse samples and damage localization is iteratively detected via sensing–processing cycles with metaheuristic sampling distribution updating. Specifically, simulated annealing and ant colony analogy are used for guidance in future selection of sensing locations. This framework is subsequently validated by numerical and experimental implementations for gusset plate crack identification. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-06T02:35:40.21143-05:0
      DOI: 10.1002/stc.1881
       
  • Simultaneous identification of stiffness, mass, and damping using an
           on‐line model updating approach
    • Abstract: The development of damage identification methods that enable rapid implementation holds great promise for assessing structural integrity to avoid further damage or catastrophic failure. Here, an on‐line model updating approach is proposed to rapidly and simultaneously identify the mass, stiffness, and damping properties of a structural model. The proposed approach facilitates identification of these unknown parameters using two steps: first, energy equilibrium equations are used to establish a relationship between structural energy and unknown parameters; second, the Kalman filter is adopted to obtain the unknown parameters in a short period of time. Numerical verification is conducted on a 158‐degree‐of‐freedom truss model with 324 unknown parameters based on a real‐world structure. The results indicate that the proposed approach can simultaneously identify the model parameters for the mass, stiffness, and damping of both the damaged and undamaged structures online, and also can effectively identify the stiffness damage and mass change, even in an environment with noise. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-03T02:05:45.606515-05:
      DOI: 10.1002/stc.1892
       
  • Traffic volume estimation in a cable‐stayed bridge using dynamic
           responses acquired in the structural health monitoring
    • Authors: Kaiwan Wattana; Mayuko Nishio
      Abstract: This paper presents the traffic volume estimation by constructing a statistical model using dynamic response data acquired by a structural health monitoring system installed on an in‐service cable‐stayed bridge. The structural health monitoring system consists of various sensors, including accelerometers, tilt sensors, temperature sensors, and the vehicle counting system. In this paper, the correlations between the response features from dynamic data, peak frequencies and amplitudes of responses, and the temperature and the traffic volume were firstly investigated. The results revealed that the traffic volume was a dominant factor that influenced on variances of the extracted features, while the temperature showed low effects on them in the target bridge. Some of the response features that showed high correlations were then selected for constructing a linear regression model to estimate the total traffic volume per 5 min. The constructed model then showed the accurate fitting performance to the data, and it was also capable of predicting the traffic volume on the bridge. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-31T23:50:44.522429-05:
      DOI: 10.1002/stc.1890
       
  • Genetic‐based EM algorithm to improve the robustness of Gaussian mixture
           models for damage detection in bridges
    • Abstract: During the service life of bridges, the bridge management systems (BMSs) seek to handle all performed assessment activities by controlling regular inspections, evaluations, and maintenance of these structures. However, the BMSs still rely heavily on qualitative and visual bridge inspections, which compromise the structural evaluation and, consequently, the maintenance decisions as well as the avoidance of bridge collapses. The structural health monitoring appears as a natural field to aid the bridge management, providing more reliable and quantitative information. Herein, the machine learning algorithms have been used to unveil structural anomalies from monitoring data. In particular, the Gaussian mixture models (GMMs), supported by the expectation‐maximization (EM) on the parameter estimation, have been proposed to model the main clusters that correspond to the normal and stable state conditions of a bridge, even when it is affected by unknown sources of operational and environmental variations. Unfortunately, the performance of the EM algorithm is strongly dependent on the choice of the initial parameters. This paper proposes a hybrid approach based on a standard genetic algorithm (GA) to improve the stability of the EM algorithm on the searching of the optimal number of clusters and their parameters, strengthening the damage classification performance. The superiority of the GA‐EM‐GMM approach, over the classic EM‐GMM one, is tested on a damage detection strategy implemented through the Mahalanobis‐squared distance, which permits one to track the outlier formation in relation to the chosen main group of states, using real‐world data sets from the Z‐24 Bridge, in Switzerland. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-29T23:05:39.214157-05:
      DOI: 10.1002/stc.1886
       
  • Damage detection for high‐speed train axle based on the propagation
           characteristics of guided waves
    • Authors: Jianxi Qiu; Fucai Li, Jifeng Wang
      Abstract: The currently defect identification techniques based on guided wave is not feasible for high‐speed train axle because the structure complicates wave propagation. A novel damage detection method especially for train axle is proposed in this paper. Piezoelectric patches are used as actuator to excite waves in the axle. Guided wave generated by single actuator and circumferential, limited number of actuator configurations is discussed to optimize the transducer network. The axle is simplified to a variable cross‐sectional and thick‐walled hollow cylindrical structure. Eight piezoelectric actuators that evenly distributed at the axle end surface are used to excite simplex longitudinal waves. Signals of circumferential and axial displacement of the monitoring points are researched before and after introducing the flaw on the surface, and their sensitivity to the depth and length of defect are also discussed. From the view of practical feasibility, the difference of signals from two axisymmetrical measure points of same axial position is proposed for the defect identification. Experimental verification is conducted, and the results demonstrate that the proposed approach is reliable in the axle inspection. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-29T22:40:41.038835-05:
      DOI: 10.1002/stc.1891
       
  • Identification of time‐varying cable tension forces based on adaptive
           sparse time‐frequency analysis of cable vibrations
    • Authors: Yuequan Bao; Zuoqiang Shi, James L. Beck, Hui Li, Thomas Y. Hou
      Abstract: For cable bridges, the cable tension force plays a crucial role in their construction, assessment and long‐term structural health monitoring. Cable tension forces vary in real time with the change of the moving vehicle loads and environmental effects, and this continual variation in tension force may cause fatigue damage of a cable. Traditional vibration‐based cable tension force estimation methods can only obtain the time‐averaged cable tension force and not the instantaneous force. This paper proposes a new approach to identify the time‐varying cable tension forces of bridges based on an adaptive sparse time‐frequency analysis method. This is a recently developed method to estimate the instantaneous frequency by looking for the sparsest time‐frequency representation of the signal within the largest possible time‐frequency dictionary (i.e. set of expansion functions). In the proposed approach, first, the time‐varying modal frequencies are identified from acceleration measurements on the cable, then, the time‐varying cable tension is obtained from the relation between this force and the identified frequencies. By considering the integer ratios of the different modal frequencies to the fundamental frequency of the cable, the proposed algorithm is further improved to increase its robustness to measurement noise. A cable experiment is implemented to illustrate the validity of the proposed method. For comparison, the Hilbert–Huang transform is also employed to identify the time‐varying frequencies, which are then used to calculate the time‐varying cable‐tension force. The results show that the adaptive sparse time‐frequency analysis method produces more accurate estimates of the time‐varying cable tension forces than the Hilbert–Huang transform method. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-29T22:35:37.479509-05:
      DOI: 10.1002/stc.1889
       
  • Dynamic investigation of a large historical cathedral
    • Authors: Ahmed Elyamani; Oriol Caselles, Pere Roca, Jaime Clapes
      Abstract: The presented research aimed at studying the dynamic behavior of Mallorca cathedral (Mallorca Island, Spain) under ambient sources of vibration and seismic events. The cathedral is one of the greatest built masonry structures worldwide. It is characterized for its audacious dimensions and slender structural members. Because of it, the study of its dynamic behavior is a clear concern. The cathedral dynamic properties were firstly identified using ambient vibration testing. Afterwards, a dynamic monitoring system was implemented to continuously measure, record, and wirelessly transfer the acceleration records without having to set up an activating threshold. This monitoring type was implemented because of the low seismic intensity of Mallorca Island with a basic ground acceleration of only 0.04 g according to the Spanish seismic standard. The continuous monitoring allowed for capturing some seismic events and some drops in the natural frequencies were noticed because of a breathing crack effect. Using both ambient vibration testing and continuous monitoring system, global modes could be more accurately identified than more local ones. The identification of the global modes was more attainable than in the case of more local ones. The temperature was a more influential environmental parameter than humidity and wind for all of the identified modes except for one more directly depended on wind. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-29T22:20:55.347784-05:
      DOI: 10.1002/stc.1885
       
  • A trajectory method for vibration based damage identification of
           underdetermined problems
    • Authors: Stavros Chatzieleftheriou; Nikos D. Lagaros
      Abstract: The problem of structural damage identification based on vibration measurements (eigenfrequencies and incomplete mode shapes) is generally formulated as an inverse problem aiming to identify changes encountered on the global stiffness matrix. In most cases, the measured quantities are less than the damage parameters to be identified; thus, an infinite number of possible damage configurations are expected to satisfy the measurements. Therefore, damage identification problems are often proven to be ill‐conditioned. The problem becomes more complex when measurements' noise and model uncertainties are considered. Therefore, depending on the structural system, damage scenario and available vibration measurements, additional eigenmode data may need to be considered in order to increase the robustness of the damage identification procedure. In this work, a new two‐loop trajectory method is presented, that relies on an iterative nonlinear sensitivity analysis procedure. The main advantage of the proposed method is its ability to identify damage scenarios that match the measured data with high accuracy as well as to explore effectively the solution space. This feature can be exploited in order to assess the adequacy of the measurements in noisy and/or uncertain environment. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-26T23:35:48.701966-05:
      DOI: 10.1002/stc.1883
       
  • Optimal configurations for a linear vibration suppression device in a
           multi‐storey building
    • Authors: Sara Ying Zhang; Jason Zheng Jiang, Simon Neild
      Abstract: This paper investigates the use of a two‐terminal vibration suppression device in a building. The use of inerter‐spring‐damper configurations for a multi‐storey building structure is considered. The inerter has been used in Formula 1 racing cars and applications to various systems such as road vehicles have been identified. Several devices that incorporate inerter(s), as well as spring(s) and damper(s), have also been identified for vibration suppression of building structures. These include the tuned inerter damper and the tuned viscous mass damper. In this paper, a three‐storey building model with a two‐terminal absorber located at the bottom subjected to base excitation is studied. The brace stiffness is also taken into consideration. Four optimum absorber layouts, in terms of how spring, damper and inerter components should be arranged, for minimising the maximum relative displacements of the building are obtained with respect to the inerter's size and the brace stiffness. The corresponding parameter values for the optimum absorber layouts are also presented. Furthermore, a real‐life earthquake data is used to show the advantage of proposed absorber configurations. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-26T23:15:35.854082-05:
      DOI: 10.1002/stc.1887
       
  • Acoustic emission‐based analysis of bond behavior of corroded
           reinforcement in existing concrete structures
    • Authors: Ahmed A. Abouhussien; Assem A. A. Hassan
      Abstract: This experimental study exploits acoustic emission (AE) monitoring to assess the bond behavior of corroded bars in reinforced concrete prism samples under pull‐out tests. The analysis of AE parameters obtained in this study including amplitude, duration, cumulative number of hits, and signal strength was performed to identify different stages of bond degradation. The results of bond behavior and free end slip were analyzed and compared with the corresponding AE data. An intensity analysis of AE signal strength was also completed to quantify the bond damage using two additional AE parameters: historic index (H (t)) and severity (Sr). The outcomes of AE analysis enabled the detection of early stages of bond deterioration (micro‐cracking) as well as identification of the macro‐cracking stage prior to the occurrence of bond splitting failure. The results also showed a good correlation between AE cumulative number of hits and AE signal strength parameters with the steel‐to‐concrete bond degradation because of corrosion. Finally, the results of H (t) and Sr were employed to generate intensity classification charts to characterize the stages of micro‐ and macro‐cracking and range of slip of corroded reinforcement. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-26T23:10:34.517081-05:
      DOI: 10.1002/stc.1893
       
  • Online Bayesian model assessment using nonlinear filters
    • Authors: Thaleia Kontoroupi; Andrew W. Smyth
      Abstract: Model assessment is an integral part of many engineering applications, because any analytical or numerical mathematical model used for predictive purposes is only an approximation of the real system. The Bayesian approach to model assessment requires the calculation of the evidence of each candidate model considered given the available measured data, which is a nontrivial task, and it is usually attempted offline, e.g., by using a stochastic simulation scheme or some deterministic approximation. Very few authors, in general, and hardly any in the field of structural dynamics, have investigated online application of model assessment. The current work explores how Bayesian model assessment and an online identification scheme for joint state and parameter estimation, in particular the unscented Kalman filter, whose computational efficiency has been widely recognized, could be integrated into a single method. This hierarchical Bayesian modeling approach involves two inference levels, namely, model assessment and parameter estimation. There is the possibility of adding another level within the hierarchy for noise estimation. An illustrative example involving several hysteretic candidate models is presented to demonstrate the implementation of the proposed procedure in structural health monitoring applications. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-19T04:35:30.849928-05:
      DOI: 10.1002/stc.1880
       
  • Correlation between global damage and local damage of RC frame structures
           under strong earthquakes
    • Authors: Zheng He; Yichao Xu
      Abstract: In order to reasonably incorporate local and global monitoring response data into dynamic update in the weighted combination models for a closer correlation between global damage and local damage, a logical time‐variant correlation between global damage and local damage is established for reinforced concrete structures under strong earthquakes. Two sets of dynamic weight coefficients used to characterize the relative damage contribution of floors through modal information and energy information are suggested in the correlation. The modal information‐based weight coefficients that are defined as the normalized accumulative times of reserved floors could be capable of retaining the necessary information of relatively weak floors or sensitive regions with localized damage significance, while the energy information‐based weight coefficients based on the normalized curvature difference of ‘jerk energy’ are helpful to quantify the relative degree of floor damages accumulated by hysteretic dissipated energy. The combination factors corresponding to the proposed dynamic weight coefficients, together with static weight coefficients, are calibrated by a macroscopic global seismic damage model. The results from the example study indicate that these factors show different changing rules with increasing peak ground acceleration level. Modal information‐based weight coefficients have been found to have a desirable agreement with the inter‐story pure translation ratios. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-19T04:31:30.934734-05:
      DOI: 10.1002/stc.1877
       
  • Particle filtering and marginalization for parameter identification in
           structural systems
    • Authors: Audrey Olivier; Andrew W. Smyth
      Abstract: In structural health monitoring, one wishes to use available measurements from a structure to assess structural condition, localize damage if present, and quantify remaining life. Nonlinear system identification methods are considered that use a parametric, nonlinear, physics‐based model of the system, cast in the state‐space framework. Various nonlinear filters and parameter learning algorithms can then be used to recover the parameters and quantify uncertainty. This paper focuses on the particle filter (PF), which shows the advantage of not assuming Gaussianity of the posterior densities. However, the PF is known to behave poorly in high dimensional spaces, especially when static parameters are added to the state vector. To improve the efficiency of the PF, the concept of Rao–Blackwellisation is applied, that is, we use conditional linearities present in the equations to marginalize out some of the states/parameters and infer their conditional posterior pdf using the Kalman filtering equations. This method has been studied extensively in the particle filtering literature, and we start our discussion by improving upon and applying two well‐known algorithms on a benchmark structural system. Then, noticing that in structural systems, high nonlinearities are often localized while the remaining equations are bilinear in the states and parameters, a novel algorithm is proposed, which combines this marginalization approach with a second‐order extended Kalman filter. This new approach enables us to marginalize out all the states/parameters, which do not contribute to any high nonlinearity in the equations and, thus, improve identification of the unknown parameters. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-19T04:25:52.892868-05:
      DOI: 10.1002/stc.1874
       
  • Improving performance of a super tall building using a new
           eddy‐current tuned mass damper
    • Authors: Xilin Lu; Qi Zhang, Dagen Weng, Zhiguang Zhou, Shanshan Wang, Stephen A. Mahin, Sunwei Ding, Feng Qian
      Abstract: Two kinds of methods have been primarily used to improve the vibration performance of high‐rise buildings. One approach is to enhance the structural lateral stiffness, which may increase the component size and inefficiently use material. The other approach is to employ vibration control devices, such as tuned mass dampers (TMDs), tuned liquid dampers (TLD) and other supplemental damping devices. This latter approach has proved to be quite economical and efficient, and as such, increasingly used in practice. The Shanghai Center Tower (SHC) is a super high‐rise landmark building in China, with a height of 632 m. In order to mitigate its vibration during wind storms, a new eddy‐current TMD was installed at the 125th floor. Special protective mechanisms were incorporated to prevent excessively large amplitude motion of the TMD under extreme wind or earthquake scenarios. Results of reduced‐scale laboratory tests and field tests are presented in this paper to characterize the dynamic properties of the damping device and validate the fidelity of the numerical results. Results of structural analyses indicate that for SHC the eddy‐current TMD was able to reduce wind‐induced structural acceleration by 45%–60% and earthquake‐induced structural displacement by 5%–15%. The installation of the TMD was completed in December 2014, and the performance observed to date is judged to be good. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-18T04:12:42.556007-05:
      DOI: 10.1002/stc.1882
       
  • A model‐based method for damage detection with guided waves
    • Abstract: Defect detection techniques, which utilise guided waves, have received significant attention over the past twenty years. Many of these techniques implement the baseline signal subtraction approach for damage diagnosis. In this approach, the baseline signal previously recorded for a defect‐free structure is compared with/or subtracted from the actual signal recorded during routine inspections. A significant deviation between these two signals (or residual signal/time‐trace) can be treated as an indication of the presence of critical damage. However, the accuracy of this common approach can be compromised by various uncontrolled factors, which include ambient temperature variations, unavoidable inconsistencies in the PZT installation procedure and degradation of mechanical properties with time. This paper presents a new method for reconstruction of the baseline signal, which can compensate for the above influences and improve the accurateness of damage diagnosis. The method utilises 3D laser vibrometry measurements in conjunction with high‐fidelity FE simulations. This paper also describes an application of this method to the reconstruction of the baseline signal and detection of damage in beam and plate structures. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-18T04:12:11.718728-05:
      DOI: 10.1002/stc.1884
       
  • Assessing the effect of nonlinearities on the performance of a tuned
           inerter damper
    • Abstract: In this paper, the use of a tuned inerter damper (TID) as a vibration absorber is studied numerically and experimentally, with civil engineering applications in mind. Inerters complete the analogy between mechanical and electrical networks, as the mechanical element equivalent to a capacitor and were developed in the 2000s. Initially, inerters were used for applications in automotive engineering, where they are known as J‐dampers. Recently, research has suggested that inerter‐based networks could be used for civil engineering applications, offering interesting advantages over traditional tuned mass dampers. In the civil engineering context, research has been mainly theoretical, considering ideal inerters. Because the dynamics of an inerter device include nonlinearities, especially at the low frequencies associated with civil engineering applications, the performance of the TID device using an off‐the‐shelf inerter has been experimentally tested in the work presented here. The chosen system, comprising a host structure with a TID attached to it, was tested using real‐time dynamic substructuring (RTDS) or hybrid testing. The inerter was tested physically, while the remaining components of the TID device, the spring and damper, together with the host structure, were simulated numerically. Displacements and forces at the interface between numerical and physical components are updated in real time. This numerical–physical split allows the optimisation of the TID parameters, because the values of the spring and the damper can be changed without altering the experimental setup. In addition, this configuration takes into account the inerter's potentially complex dynamics by testing it experimentally, together with the characteristics of the host structure. Developing RTDS tests for physical inertial substructures, where part of the fed back interface forces are proportional to acceleration, is a challenging task because of delays arising at the interface between the experimental and the numerical substructures. Problems associated with stability issues caused by delay and causality arise, because we are dealing with neutral and advanced delayed differential equations. A new approach for the substructuring algorithm is proposed, consisting of feeding back the measured force deviation from the ideal inerter instead of the actual force at the interface. The experimental results show that with appropriate retuning of the components in the TID device, the performance in the TID incorporating the real inerter device is close to the ideal inerter device. © 2016 The
      Authors . Structural Control and Health Monitoring published by John Wiley & Sons, Ltd.
      PubDate: 2016-05-15T22:40:32.973161-05:
      DOI: 10.1002/stc.1879
       
  • Real‐time experimental validation of a novel semi‐active control
           scheme for vibration mitigation
    • Authors: Mohammad S. Miah; Eleni N. Chatzi, Vasilis K. Dertimanis, Felix Weber
      Abstract: This study performs an experimental investigation of a novel, semi‐active control strategy for effective vibration mitigation. The implemented approach comprises a combination of the linear quadratic regulator with a nonlinear observer, namely, the unscented Kalman filter, for the control of systems described by uncertainties. Indeed, numerical models of structural systems often result as inadequate because of inherent uncertainties, such as noise, modeling errors, unknown system properties, or influence of varying operational and environmental conditions. In tackling this issue, the unscented Kalman filter is herein employed for adaptive joint state and parameter estimation refining the accuracy of the model employed by the controller and resulting in enhanced vibration mitigation. A scaled five‐story shear frame attached to a hydraulic cylinder comprises the tested structure, where actuation is provided by means of a rotational magnetorheological damper operating on the relative motion between the ground floor and the first floor plate. The experimentally obtained results demonstrate a good agreement with simulations and encourage further implementation of the proposed framework in field applications of structural control. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-15T22:35:57.414218-05:
      DOI: 10.1002/stc.1878
       
  • Vibration‐based system identification of wind turbine system
    • Abstract: The goal of this study was to investigate the use of vibration‐based system identification methods for detecting wind turbine blade delamination during operating conditions and when subjected to other excitations such as earthquake ground motion. In particular, multivariate singular spectrum analysis and two subspace identification techniques were tested for detecting the dynamic characteristics of the wind blade. A total of two series of experiments was conducted to verify the proposed algorithms. In both cases, accelerometers were installed on the blades for measuring their vibration response. The first test series were performed in the laboratory; a motor spun a small‐scale customized wind turbine at controlled angular velocities, and the shaking table excited the entire structure. Artificial damage was introduced by loosening bolts at the blade‐rotor connection. The second test was conducted in the field, and vibration data was collected from an operating small‐scale wind turbine. The blade's vibration response was analyzed through time‐frequency analyses and subspace identification. These tests confirmed that the estimation of dynamic characteristics of blade and rotating frequency of the turbine system was feasible, and the results will guide future monitoring studies planned for larger‐scale systems. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-10T03:15:55.377285-05:
      DOI: 10.1002/stc.1876
       
  • Distributed sensing of a masonry vault during nearby piling
    • Authors: Sinan Acikgoz; Loizos Pelecanos, Giorgia Giardina, James Aitken, Kenichi Soga
      Abstract: Piles were constructed inside historic brick barrel vaults during the London Bridge Station Redevelopment. In order to ensure safe operation of the tracks above, movements of the vaults were monitored regularly by total stations. Concurrently, two distributed sensing technologies, fibre optic cables and laser scanners, were used to investigate the vault response to settlements. This paper discusses the monitoring data retrieved from these ‘point’ and ‘distributed’ sensing technologies and evaluates their use in structural assessment. The total station data are examined first. It is characterized by high precision and limited spatial coverage due to the use of optical targets. As a result, the total station data are useful for threshold detection but do not provide a detailed understanding of structural response or damage. In contrast, by utilizing distributed fibre optic sensors based on Brillouin optical domain reflectometry, the strain development in the structure during piling is quantified. The location and width of resulting crack openings are also determined, providing useful indicators for damage evaluation. The comparison of point clouds from laser scanners obtained at different stages of pile construction further expands the spatial coverage by detecting global movement of the structure on all visible surfaces. Using these data, the two hinge‐response mechanism of the vault is revealed. The rich distributed data enable the calibration of the 2D mechanism and the finite element models, elucidating the contribution of arch stiffness, arch and backfill interaction, potential lateral movements and inter‐ring sliding to the response. © 2016 The
      Authors . Structural Control and Health Monitoring published by John Wiley & Sons, Ltd.
      PubDate: 2016-05-10T03:00:37.839851-05:
      DOI: 10.1002/stc.1872
       
  • Efficient optimal design and design‐under‐uncertainty of passive
           control devices with application to a cable‐stayed bridge
    • Authors: Subhayan De; Steven F. Wojtkiewicz, Erik A. Johnson
      Abstract: Structures today may be equipped with passive structural control devices to achieve some performance criteria. The optimal design of these passive control devices, whether via a formal optimization algorithm or a response surface parameter study, requires multiple solutions of the dynamic response of that structure, incurring a significant computational cost for complex structures. These passive control elements are typically point‐located, introducing a local change (possibly nonlinear, possibly uncertain) that affects the global behavior of the rest of the structure. When the structure, other than these localized devices, is linear and deterministic, conventional solvers (e.g., Runge–Kutta, MATLAB's ode45, etc.) ignore the localized nature of the passive control elements. The methodology applied in this paper exploits the locality of the uncertain and/or nonlinear passive control element(s) by exactly converting the form of the dynamics of the high‐order structural model to a low‐dimensional Volterra integral equation. Design optimization for parameters and placement of linear and nonlinear passive dampers, tuned mass dampers, and their combination, as well as their design‐under‐uncertainty for a benchmark cable‐stayed bridge, is performed using this approach. For the examples considered herein, the proposed method achieves a two‐orders‐of‐magnitude gain in computational efficiency compared with a conventional method of comparable accuracy. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-06T00:50:43.953337-05:
      DOI: 10.1002/stc.1846
       
  • Adaptive block backstepping control for civil structures with unknown
           parameters subjected to seismic excitation
    • Authors: Pedram Ghaderi; Fereidoun Amini
      Abstract: This paper presents an active control scheme for structures with unknown parameters subjected to ground acceleration. It is assumed that the mass, stiffness and damping matrices are unknown to the designer, and no measurement of the ground acceleration is available. Instead, the displacement and velocity vectors are accessible for control purposes. Adaptive block backstepping is used to propose a control force vector which makes the response of the structure follow a predefined reference signal as closely as possible. The provided numerical examples in this paper show the admissible performance of the proposed closed‐form solution for the control force. The benefits and drawbacks of this approach are discussed as well. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-04T03:01:52.512187-05:
      DOI: 10.1002/stc.1875
       
  • Set‐membership identification technique for structural damage based on
           the dynamic responses with noises
    • Authors: Qinghe Shi; Xiaojun Wang, Lei Wang, Yunlong Li, Xiao Chen
      Abstract: Based on the availability of measured acceleration signals of structures, the interval analysis technique and set‐membership identification concept are combined to identify the structural damage in this paper. Because of the insufficiency and uncertainty of information obtained from measurements, the noises of measurements are enveloped by interval numbers. Via the first‐order Taylor series expansion, the interval bounds of the element stiffness parameters (ESPs) of both undamaged and damaged structures are derived by updating the reference finite element model. Through the intersection operations of intervals of the ESP obtained from dynamic responses in different time periods, the estimate intervals of the ESP are refined. Three damage indexes as stiffness reduce factor, possibility of damage existence, and damage measure index are introduced to identify the damage in the structure. Even though the dynamic responses are with low signal‐to‐noise ratio, the injury of structure can be detected by the proposed method. Two numerical examples and an experimental example are performed to demonstrate the feasibility and effectiveness of the proposed technique. The results show that the proposed method can improve the accuracy of damage diagnosis compared with the deterministic damage identification method. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-04T02:56:41.287311-05:
      DOI: 10.1002/stc.1868
       
  • Real‐time control of shake tables for nonlinear hysteretic systems
    • Authors: Ki P. Ryu; Andrei M. Reinhorn
      Abstract: Shake table testing is an important tool to challenge integrity of structural and non‐structural specimens by imposing excitations at their base. When shake tables are loaded with specimens, the interaction between the tables and specimens influences the system dynamics that may result in undesired performance. In order to compensate the effects of the interaction, open loop feedforward compensation methods have been widely used successfully in current practice of table controls, assuming that the specimens remain linear. On the contrary, unsatisfactory signal performances during shake table testing were observed when flexible and heavy specimens experience nonlinear behavior. While lack of high fidelity might be acceptable for the purpose of exploration research of specimens subjected to random excitations, a high fidelity of signal reproduction is necessary for shake table qualification testing where specific target motion is required to challenge the specimens. In this study, a nonlinear tracking control scheme based on the feedback linearization method is proposed for the control of shake tables to simulate target motions at specific locations of test structures, having nonlinear hysteretic behavior. Additionally, a real‐time estimator using the extended Kalman filter is adopted and combined with the controller in order to account for the changes and uncertainties in system models due to nonlinearities and yielding caused by extreme excitations. The proposed adaptive tracking control method has been applied to a realistic shake table–structure test setup by means of numerical simulations, and the results show good tracking and estimation performance. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-04T02:56:20.901021-05:
      DOI: 10.1002/stc.1871
       
  • Modeling and analysis of a structure semi‐active tuned liquid damper
           system
    • Authors: I. M. Soliman; M. J. Tait, A. A. El Damatty
      Abstract: A tuned liquid damper (TLD), which is similar to a tuned mass damper (TMD), is a type of dynamic vibration absorber (DVA) that can be employed to reduce wind induced resonant vibrations of a structure. Improved TLD performance could be realized by equipping TLDs with variable energy dissipating capabilities such as damping screens, which can be adjusted through a certain mechanism, permitting optimal control performance to be maintained over a wide range of loading conditions in a semi‐active mode of control. In this paper, a control strategy based on a gain scheduling scheme is utilized by controlling the inclination angle of the damping screen(s) and consequently the screen loss coefficient value(s). The gain scheduling control strategy is employed on a simple single‐story structure equipped with a semi‐active TLD (SA‐TLD) in order to maintain the optimal damping value (ζTLD − opt) based on averaged or instantaneous structural response tracking and a prescribed look‐up table. Results are assessed using experimental values from tests conducted on conventional passive TLDs. A performance comparison between a semi‐active TLD control system and a conventional passive TLD control system is carried out. The fluid response amplitude for a SA‐TLD is also investigated and compared to that of a passive TLD. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-04T02:51:35.520825-05:
      DOI: 10.1002/stc.1865
       
  • Issue Information
    • Pages: 1147 - 1149
      Abstract: No abstract is available for this article.
      PubDate: 2016-08-02T01:51:34.952259-05:
      DOI: 10.1002/stc.1794
       
  • Theoretical prediction of the dynamic behavior of rolling‐ball
           rubber‐layer isolation systems
    • Authors: Alessandra Fiore; Giuseppe Carlo Marano, Maria Gabriella Natale
      Pages: 1150 - 1167
      Abstract: This paper presents the results of a theoretical study carried out to characterize the dynamic behavior of a seismic isolation system consisting of steel‐rolling balls on rubber layers. This type of device reduces seismic hazard during earthquakes by decoupling the superstructure from the ground motion and by dissipating the energy in damping, thanks to the viscous‐elastic properties of the rubber. The behavior of the rolling balls on rubber layers isolation system is described by achieving suitable expressions for the resultant normal and shear forces acting in the device. In particular, it is shown how the resultant shear force is highly affected by the correct definition of the slip and stick regions, which develop at the steel‐rubber contact area. The analysis allows to identify the main parameters characterizing this type of device, furnishing a valid tool in order to correctly calculate some response quantities significantly influenced by the isolation system. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-19T21:23:04.823953-05:
      DOI: 10.1002/stc.1830
       
  • Bridge related damage quantification using unmanned aerial vehicle imagery
    • Authors: A. Ellenberg; A. Kontsos, F. Moon, I. Bartoli
      Pages: 1168 - 1179
      Abstract: Visual inspection procedures remain the primary method of infrastructure assessment throughout the USA, but their shortcomings are numerous. In addition to their widely acknowledged variability and subjectivity, the large scale of civil infrastructure systems presents expensive access and time requirements that constrain the frequency of visual inspections and result in poor temporal resolution, which hampers effective decision‐making. To overcome this challenge, the research reported herein aimed to assess the ability of computer algorithms together with imagery collected by unmanned aerial vehicles (UAV) to extract accurate and quantitative information to help inform infrastructure management decisions. Techniques such as homography and lens distortion correction are used in this article in a post‐processing framework that allows the use of color images obtained by UAVs for actual damage quantification measurements. The experiments described in this article utilize a UAV with a mounted camera and provide measurements from a representative infrastructure mockup with several simulated damage scenarios. Deformation measurements, change detection (related to structural features and the size of deterioration), and crack pattern identification were all analyzed. The results indicated that the developed post‐processing algorithms were able to extract quantitative information from UAV captured imagery. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-20T03:27:55.397696-05:
      DOI: 10.1002/stc.1831
       
  • Mode shape‐based damage detection in plate structure without
           baseline data
    • Authors: Sandris Rucevskis; Rims Janeliukstis, Pavel Akishin, Andris Chate
      Pages: 1180 - 1193
      Abstract: In this paper, a mode shape curvature‐based method for detection and localization of damage in plate‐like structures is described. The proposed algorithm requires only the mode shape curvature data of the damaged structure. The damage index is defined as the absolute difference between the measured curvature of the damaged structure and the smoothed polynomial representing the curvature of the healthy structure. To examine the advantages and limitations of the proposed method, several sets of numerical simulations are carried out. Simulated test cases considering different levels of damage severity, measurement noise and sensor sparsity are studied to evaluate the robustness of the method under the noisy experimental data and limited sensor data. Applicability and effectiveness of the proposed damage detection method are further demonstrated experimentally on an aluminium plate containing mill‐cut damage. The modal frequencies and the corresponding mode shapes are obtained via finite element models for numerical simulations and by using a scanning laser vibrometer for the experimental study. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-20T03:34:01.608609-05:
      DOI: 10.1002/stc.1838
       
  • Application of stochastic subspace identification for stay cables with an
           alternative stabilization diagram and hierarchical sifting process
    • Pages: 1194 - 1213
      Abstract: The modal parameters of numerous modes for a stay cable are usually required in engineering practice. The application of conventional stochastic subspace identification techniques without delicate cautions, however, has been found to be unsuccessful in this case. Aiming to attack such a difficulty, this study establishes a new methodology based on the covariance type of stochastic subspace identification for extensively identifying the modal parameters of a stay cable. Several details of choosing the parameters in performing stochastic subspace identification are first discussed. An important discovery is that the lower limit for setting the time lag parameter can be decided by the ratio of the fundamental period of cable to the sampling time increment for a valid identification with the conventional stabilization diagram. Inspired by the aforementioned criterion, an alternative stabilization diagram is further proposed to more conveniently distinguish stable modal parameters of cable. A hierarchical sifting process including three stages is then developed to systematically and automatically extract reliable modal parameters from the alternative stabilization diagram. Demonstrated by analyzing the ambient vibration measurements for three stay cables of Chi‐Lu Bridge, the feasibility of this new approach is verified with successfully obtaining the modal frequencies, damping ratios, and mode shape ratios for almost all the cable modes in the examined frequency range. Another interesting finding is that the modal frequencies and damping ratios of bridge deck can also be effectively identified from the ambient vibration signals of cable. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-28T02:30:18.749401-05:
      DOI: 10.1002/stc.1836
       
 
 
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