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ENERGY (185 journals)                  1 2 | Last

Advances in Building Energy Research     Hybrid Journal   (Followers: 11)
Advances in Energy and Power     Open Access   (Followers: 3)
Advances in High Energy Physics     Open Access   (Followers: 11)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 15)
American Journal of Energy Research     Open Access   (Followers: 7)
Annals of Nuclear Energy     Hybrid Journal   (Followers: 7)
Annual Reports on NMR Spectroscopy     Full-text available via subscription   (Followers: 1)
Annual Review of Resource Economics     Full-text available via subscription   (Followers: 11)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Solar Energy     Hybrid Journal   (Followers: 12)
Archives of Thermodynamics     Open Access   (Followers: 4)
Artificial Photosynthesis     Open Access  
Atomic Energy     Hybrid Journal   (Followers: 5)
Atoms for Peace: an International Journal     Hybrid Journal   (Followers: 3)
Batteries     Open Access   (Followers: 1)
Biofuel Research Journal     Open Access   (Followers: 2)
Biofuels     Hybrid Journal   (Followers: 9)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 6)
Bulletin de droit nucleaire     Full-text available via subscription   (Followers: 1)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 13)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbon Management     Hybrid Journal   (Followers: 6)
Catalysis for Sustainable Energy     Open Access   (Followers: 3)
CERN courier. International journal of high energy physics     Free   (Followers: 1)
Chain Reaction     Full-text available via subscription  
Clefs CEA     Full-text available via subscription   (Followers: 1)
Computational Water, Energy, and Environmental Engineering     Open Access   (Followers: 2)
Current Sustainable/Renewable Energy Reports     Hybrid Journal   (Followers: 3)
Dams and Reservoirs     Hybrid Journal   (Followers: 4)
Development of Energy Science     Open Access   (Followers: 4)
Distributed Generation & Alternative Energy Journal     Hybrid Journal   (Followers: 1)
E3S Web of Conferences     Open Access  
Economics and Policy of Energy and the Environment     Full-text available via subscription   (Followers: 4)
Electrical and Power Engineering Frontier     Open Access   (Followers: 10)
Energy     Partially Free   (Followers: 25)
Energy & Fuels     Full-text available via subscription   (Followers: 25)
Energy and Buildings     Hybrid Journal   (Followers: 7)
Energy and Emission Control Technologies     Open Access   (Followers: 1)
Energy and Environment Focus     Free  
Energy and Environment Research     Open Access   (Followers: 10)
Energy and Environmental Engineering     Open Access   (Followers: 1)
Energy and Power     Open Access   (Followers: 3)
Energy and Power Engineering     Open Access   (Followers: 10)
Energy Conversion and Management     Hybrid Journal   (Followers: 10)
Energy Efficiency     Hybrid Journal   (Followers: 12)
Energy Harvesting and Systems : Materials, Mechanisms, Circuits and Storage     Hybrid Journal   (Followers: 1)
Energy Journal The     Full-text available via subscription   (Followers: 1)
Energy Law Journal     Full-text available via subscription   (Followers: 3)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 16)
Energy Policy     Partially Free   (Followers: 48)
Energy Prices and Taxes     Full-text available via subscription   (Followers: 5)
Energy Procedia     Open Access   (Followers: 3)
Energy Reports     Open Access   (Followers: 1)
Energy Research & Social Science     Full-text available via subscription   (Followers: 1)
Energy Science & Engineering     Open Access   (Followers: 4)
Energy Science and Technology     Open Access   (Followers: 12)
Energy Strategy Reviews     Partially Free   (Followers: 6)
Energy Studies Review     Open Access   (Followers: 4)
Energy Systems     Hybrid Journal   (Followers: 11)
Energy Technology     Partially Free   (Followers: 3)
Energy Technology & Policy     Open Access  
Energy, Sustainability and Society     Open Access   (Followers: 18)
Environmental Progress & Sustainable Energy     Hybrid Journal   (Followers: 6)
EPJ Photovoltaics     Open Access   (Followers: 2)
Facta Universitatis, Series : Electronics and Energetics     Open Access  
Frontiers in Energy     Hybrid Journal   (Followers: 4)
Frontiers in Energy Research     Open Access   (Followers: 1)
Fuel and Energy Abstracts     Full-text available via subscription   (Followers: 5)
Functional Materials Letters     Hybrid Journal   (Followers: 1)
Gcb Bioenergy     Hybrid Journal   (Followers: 3)
Geothermal Energy     Open Access   (Followers: 1)
GeoWorld     Full-text available via subscription   (Followers: 2)
Green     Hybrid Journal   (Followers: 2)
IEA Electricity Information     Full-text available via subscription   (Followers: 6)
IEA Natural Gas Information     Full-text available via subscription   (Followers: 4)
IEEE Power and Energy     Full-text available via subscription   (Followers: 12)
IEEE Transactions on Energy Conversion     Hybrid Journal   (Followers: 7)
IEEE Transactions on Nuclear Science     Hybrid Journal   (Followers: 7)
IEEE Transactions on Power Systems     Hybrid Journal   (Followers: 11)
IET Power Electronics     Hybrid Journal   (Followers: 14)
IngenierĂ­a EnergĂ©tica     Open Access  
Innovations : Technology, Governance, Globalization     Hybrid Journal   (Followers: 6)
International Journal of Alternative Propulsion     Hybrid Journal   (Followers: 1)
International Journal of Ambient Energy     Hybrid Journal   (Followers: 1)
International Journal of Applied Power Engineering     Open Access   (Followers: 2)
International Journal of Clean Coal and Energy     Open Access   (Followers: 4)
International Journal of Coal Science & Technology     Open Access  
International Journal of Critical Infrastructure Protection     Hybrid Journal   (Followers: 6)
International Journal of Electric and Hybrid Vehicles     Hybrid Journal   (Followers: 7)
International Journal of Emerging Electric Power Systems     Hybrid Journal   (Followers: 5)
International Journal of Emerging Multidisciplinary Fluid Sciences     Full-text available via subscription  
International Journal of Energy and Environmental Engineering     Open Access   (Followers: 2)
International Journal of Energy and Power     Open Access   (Followers: 7)
International Journal of Energy and Statistics     Hybrid Journal  
International Journal of Energy Engineering     Open Access   (Followers: 11)
International Journal of Energy Research     Hybrid Journal   (Followers: 10)
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: 6)
International Journal of Green Energy     Hybrid Journal   (Followers: 6)

        1 2 | Last

Journal Cover   Structural Control and Health Monitoring
  [SJR: 1.351]   [H-I: 26]   [5 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  [1598 journals]
  • Identification of spatio‐temporal distribution of vehicle loads on
           long‐span bridges using computer vision technology
    • Authors: Zhicheng Chen; Hui Li, Yuequan Bao, Na Li, Yao Jin
      Abstract: Identification of spatio‐temporal distribution of vehicle loads is very important for understanding the exact loading conditions and behaviors of long‐span bridges. Using computer vision technology combining the monitoring information of the weigh‐in‐motion system (WIM) at one cross‐section and the camera along the bridge, a method to identify the spatio‐temporal distribution of vehicle loads for long‐span bridges is proposed. For moving vehicles, template images were sampled from the camera video at the location of the WIM, and the weight information of the captured vehicle was extracted from the output data sheet of the WIM based on the relationship of the pass time. Template matching and particle filter techniques were used to track the moving vehicle loads on the bridge. The images were processed using the computer vision technology. The video images obtained from cameras and the weight information measured by the WIM on the Hangzhou Bay Bridge were employed in this study. The effectiveness and accuracy of the proposed algorithm were validated through the in situ field test results on the Hangzhou Bay Bridge. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-25T00:18:05.729872-05:
      DOI: 10.1002/stc.1780
  • Assessment of mechanical properties of full‐scale masonry panels
           through sonic methods. Comparison with mechanical destructive tests
    • Abstract: Sonic tests are a valid and useful non‐destructive method for qualitative characterization of masonry elements. If sonic tests are applied with the right configuration, the results can identify discontinuities in masonry sections and provide the morphology of a construction typology, contributing to the assessment of built heritage as demanded by the international recommendations on this domain. The elaboration of data from sonic tests applied to masonry structures has been essentially based on the evaluation of the P waves' propagation through the masonry thickness, that is, by using the direct sonic method, a procedure that has been calibrated for many years by different authors. However, recent studies have shown that indirect configurations through the indirect sonic impact method may be used to estimate the mechanical properties of stones masonry samples. This procedure allows assessing not only P but also R wave propagation, permitting to estimate the deformability characteristics of masonry panels. Under this research, a set of stone masonry specimens was tested using both direct and indirect sonic impact methods and later assessed through laboratory mechanical compression tests, a procedure's sequence that allow validating the sonic tests capabilities. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-25T00:09:09.99442-05:0
      DOI: 10.1002/stc.1783
  • A local excitation and measurement approach for decentralized damage
           detection using transmissibility functions
    • Authors: Dapeng Zhu; Xiaohua Yi, Yang Wang
      Abstract: In order to assess structural safety conditions, many vibration‐based damage detection methods have been developed in recent years. Among these methods, transmissibility function analysis can offer advantages in easy and low‐cost implementation, as well as independency to the magnitude and waveform of an excitation record. Harnessing these features, a decentralized structural damage detection procedure is proposed in this paper. The proposed procedure only requires measurements in one small area at a time, and thus, is ideal for using limited number of sensors upon a large‐scale structure. This study also investigates the nature of transmissibility functions for damage detection in an analytical manner, based on a chain‐like spring–mass–damper system with multiple degrees‐of‐freedom. The analytical derivation is validated through numerical simulation and laboratory experiments using mobile sensors. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-20T00:01:04.28997-05:0
      DOI: 10.1002/stc.1781
  • Efficient time synchronization for structural health monitoring using
           wireless smart sensor networks
    • Authors: Jian Li; Kirill A. Mechitov, Robin E. Kim, Billie F. Spencer
      Abstract: Wireless smart sensor networks (WSSNs) have shown great promise in structural health monitoring (SHM), because of their advantages of low cost, higher flexibility, robust data management, and ability to provide better understanding of structural behavior through dense deployment of sensors. However, implementation of wireless SHM systems poses many challenges, one of which is ensuring adequate synchronization of the collected data. This issue arises in WSSNs because each smart sensor in the network having an independent processor with its own local clock, and this clock is not necessarily synchronized with the clocks of other sensors. Moreover, even though the clocks can be accurately synchronized by exchanging time information through beacon messages, the measured data may still be poorly synchronized because of random delays from both software and hardware sources; that is, synchronized clocks do not necessarily yield synchronized sensing. Various algorithms have been proposed to achieve both synchronized clocks and sensing. However, these protocols still lack the desired performance for SHM applications for reasons of extended data collection time, temperature variations resulting in nonlinear clock drift, requirement for prompt response, and so on. In this paper, the unique features and challenges of synchronized sensing for SHM applications are discussed, followed by a numerical investigation of the effect of nonlinear clock drift on data synchronization accuracy. A new synchronized sensing strategy considering nonlinear clock drift compensation is proposed with two different implementations to meet various application requirements. Experimental results show that the proposed time synchronization approach can compensate for temperature effects on clock drift and provide efficient and accurately synchronized sensing (
      PubDate: 2015-08-19T01:24:14.864217-05:
      DOI: 10.1002/stc.1782
  • Assessment of wood structural members degradation by means of infrared
           spectroscopy: an overview
    • Authors: Anna Sandak; Jakub Sandak, Mariapaola Riggio
      Abstract: Timber structures can undergo alteration during their service life, which can be caused by mechanical, environmental or biological agents (bacteria, fungi and insects), because of the biological nature of the material. On site characterization of timber members is a very challenging task, especially assuming that both, the structure itself and material used for construction have to be evaluated. Current assessment procedures are limited to visual inspection, occasionally supported by a few instrumental analyses (such as wood moisture content measurement and drilling resistance tests). However, a clear tendency for the application of various non‐destructive techniques is observed nowadays. The paper presents an overview on the current applications of infrared spectroscopy for the characterization of various alteration phenomena in wooden artefacts. A literature review is complemented by a series of results, reported from experimental campaigns carried out by the authors. The aim of the paper is to demonstrate the applicability of the proposed method for the analysis of different degradation processes occurring in timber members, with a special attention on wood aging, weathering, biotic decay by fungi and waterlogging. Examples of spectra evaluation as well as limitation of proposed methods are presented. Case studies including classification of decay type, analysis of the weathering dynamic and characterization of waterlogged wooden samples are briefly illustrated. Practical application of spectroscopy within timber structure assessment is considered as a very important supplement to the typical information collected during ordinary tests. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-17T23:16:57.79287-05:0
      DOI: 10.1002/stc.1777
  • Optimal viscous dampers gains for structures subjected to earthquakes
    • Authors: Ido Halperin; Yuri Ribakov, Grigoriy Agranovich
      Abstract: Passive control is a known method for vibrations damping in civil structures. The simplicity and reliability of passive damping devices makes them a worthy candidate in many practical applications. However, despite of its practical simplicity, the optimal design of passive controller is quite a hard computational problem. In this work, an enhanced optimal viscous passive dampers design method is proposed for seismically excited structures. The optimization is carried out with relation to performance index that consists of an H2 norm of the system and a quadratic gains norm. An algorithm is suggested for the look after a candidate optimum. It is based on Newton's optimization method with recently developed effective calculation method for the Hessian matrix. Numerical evaluation of the suggested method demonstrates a very fast convergence rate of the design algorithm and proves a performance effective dampers distribution. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-17T22:52:49.1871-05:00
      DOI: 10.1002/stc.1779
  • Damage identification in aluminum beams using support vector machine:
           Numerical and experimental studies
    • Authors: Satish B. Satpal; Anirban Guha, Sauvik Banerjee
      Abstract: Support vector machine (SVM) has been established as a promising tool for classification and regression in many research fields recently. In the current research work, SVM is explored to find damage locations in aluminum beams using simulation data and experimental data. Displacement values corresponding to the first mode shape of the beam are used to predict the damage locations. Two boundary conditions namely fixed‐free and fixed‐fixed are considered for this study. Damages are introduced in the form of rectangular notches along the width of the beam at different locations. Numerical simulations using commercially available finite element (FE) package, Abaqus® are first carried out on beam and mode shape data is extracted to train and test SVM with and without noise in data. To validate the predictions of damage locations based on simulation data, actual experimentations are conducted on aluminum beams of identical dimensions and boundary conditions. In the experimental study, a Laser Doppler Vibrometer (LDV) is used to extract the mode shape data. It is shown that SVM is capable to predict damage locations with a good accuracy and can be used as a promising tool in the field of structural health monitoring (SHM). Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-06T12:17:51.190114-05:
      DOI: 10.1002/stc.1773
  • Semi‐active vibration control of structural systems based on a
           reference active control law: output emulation approach
    • Authors: Kazuhiko Hiramoto; Taichi Matsuoka, Katsuaki Sunakoda
      Abstract: A new semi‐active control strategy that approximates a predicted control output of a reference active control is proposed. A variable parameter of a semi‐active control device is selected at every time instant so that the predicted control output of the semi‐active control system becomes close to the corresponding predicted control output of the reference active control as much as possible. Parameters of the reference active control law are optimized in the premise of the aforementioned ‘output emulation’ strategy so that the control performance of the semi‐active control becomes good and the ‘error’ in the sense of achieved control performance between the reference active control and semi‐active control systems becomes small. A pole placement method based on a linear matrix inequality (LMI) framework is adopted as the reference active control law. Parameters to determine the domain in the complex plane where the closed‐loop poles are placed are searched so that control performance of the semi‐active control system based on the output emulation approach is optimized. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-31T02:28:19.16465-05:0
      DOI: 10.1002/stc.1770
  • Sparse representation of ultrasonic guided‐waves for robust damage
           detection in pipelines under varying environmental and operational
    • Authors: Matineh Eybpoosh; Mario Berges, Hae Young Noh
      Abstract: The challenges of guided‐wave based structural health monitoring can be discussed under three headings: (a) multiple modes, (b) multi‐path reflections, and (c) sensitivity to environmental and operational conditions (EOCs). The objective of this paper is to develop damage detection methods that simplify guided‐wave signals while retaining damage information and have low sensitivity to EOC variations. A supervised method is proposed for damage detection. The detection performance is maximized, by imposing a sparsity constraint on the signals. This paper reports a diverse set of laboratory and field experiments validating the extent to which EOC variations, as well as damage characteristics can influence the discriminatory power of the damage‐sensitive features. The laboratory setup includes an aluminum pipe with temperature varying between 24 and 38 ° C. The method is further validated using an operational hot water supply piping system of different size and configuration than the one used in the laboratory, which operates under noisy environment, with constantly varying flow rate, temperature, and inner pressure. Moreover, the proposed method is used to detect occurrence of consecutive actual damages, namely, a crack and a mass loss as small as 10% and 8% of the wall thickness, respectively. The validation results suggest that a simple binary‐labeled training data (i.e., undamaged/damaged), obtained under a limited range of EOCs, are sufficient for the proposed method. That is, the detection method does not require prior knowledge about the characteristics of the damage (e.g., size, type, and location), and/or a training dataset that is obtained from a wide range of EOCs. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-29T04:02:15.939173-05:
      DOI: 10.1002/stc.1776
  • Discussion of system intrinsic parameters of tuned mass dampers used for
           seismic response reduction
    • Authors: Julio C. Miranda
      Abstract: Assimilating the structures incorporating tuned mass dampers to 2‐degrees‐of‐freedom mechanical systems, this paper discusses the salient parameters defining the efficiency of these devices when affixed to structures for the purpose of seismic response reduction. Focusing on parameters that are intrinsic to the mechanical systems and independent of ground motions, numerical and analytical expressions are first obtained for the modal damping of the systems. Subsequently, it is proposed that the highest efficiency in terms of modal damping allocation is achieved at tuning that results in modal damping that is in the same proportion as the participation factors for the modes. Further, some properties of the frequencies, tuning, and participation factors are analytically demonstrated. Finally, limited numerical calculations using a spectrum‐compatible accelerogram are offered to support the proposed method for modal damping allocation. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-28T04:24:24.891963-05:
      DOI: 10.1002/stc.1775
  • Damage detection with small data set using energy‐based nonlinear
    • Abstract: This study proposes a new algorithm for damage detection in structures. The algorithm employs an energy‐based method to capture linear and nonlinear effects of damage on structural response. For more accurate detection, the proposed algorithm combines multiple damage sensitive features through a distance‐based method by using Mahalanobis distance. Hypothesis testing is employed as the statistical data analysis technique for uncertainty quantification associated with damage detection. Both the distance‐based and the data analysis methods have been chosen to deal with small size data sets. Finally, the efficacy and robustness of the algorithm are experimentally validated by testing a steel laboratory prototype, and the results show that the proposed method can effectively detect and localize the defects. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-28T04:16:45.773728-05:
      DOI: 10.1002/stc.1774
  • Investigating the use of Targeted‐Energy‐Transfer devices for
           stay‐cable vibration mitigation
    • Abstract: Free vibrations of a taut cable with an attached passive Targeted‐Energy‐Transfer (TET) device are investigated using an analytical formulation of the complex generalized eigenvalue problem. This problem is of considerable practical interest in the context of stay‐cable vibration suppression in bridges, induced by wind, rain–wind and parametric excitation. The TET device is a nonlinear apparatus, which has been investigated and successfully applied to the vibration suppression in several structural or mechanical systems. This study proposes, for the first time, the use of the TET device as a simple passive apparatus for stay‐cable vibration mitigation. In this application, the device was modelled as a dashpot with a viscous damper in parallel with a power‐law nonlinear elastic spring element and a lumped mass restrained to one end. The ‘flexibility of the support’ (imperfect anchorage to the deck) was also simulated by placing an elastic support (linear elastic spring) in series between the dashpot and the deck. The study derives a new family of ‘universal design curves’ for the TET device, by accounting for the effects of nonlinear elastic stiffness, lumped mass and flexibility of the support. To verify the adequacy of the universal curves and to evaluate the effectiveness of the TET devices, parametric numerical simulations were performed on a reference stay cable. As an application example, analytical results were employed to design the dampers of one flexible stay, installed on an existing cable‐stayed bridge. In all the investigations, theoretical and numerical results were obtained and compared. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-24T02:31:06.864642-05:
      DOI: 10.1002/stc.1772
  • Issue Information
    • Abstract: No abstract is available for this article.
      PubDate: 2015-07-23T03:21:35.385631-05:
      DOI: 10.1002/stc.1702
  • Distributed fiber optic sensors for monitoring pressure and stiffness
           changes in out‐of‐round pipes
    • Authors: Kenneth Lim; Leslie Wong, Wing Kong Chiu, Jayantha Kodikara
      Abstract: Distributed fiber optic sensors have been shown to be promising when used to monitor the structural health of pipes. The body of work thus far has only considered pipes whose cross sections are assumed to remain circular under load. In some applications, the cross section of the pipe has been known to deform when loaded. Subsequent loading on a deformed pipe then generates additional stresses that may have been unaccounted for when designing the pipe. This paper addresses the effects of the initial non‐circular cross section of a pipe under internal pressure and its detection with a distributed fiber optic sensor based on Brillouin Optical Time Domain Analysis. This ability of the Brillouin Optical Time Domain Analysis sensor to detect local stiffness irregularities on an out‐of‐round pipe subjected to internal pressures is also demonstrated. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-15T02:06:13.682052-05:
      DOI: 10.1002/stc.1771
  • A frequency response‐based structural damage identification using
           model updating method
    • Authors: Fariba Shadan; Faramarz Khoshnoudian, Akbar Esfandiari
      Abstract: Structural model updating by estimation of stiffness and mass parameters via monitoring of dynamic characteristics has attracted much attention in recent decades. In this study, frequency response functions (FRF) are utilized in order to identify unknown structural parameters using a sensitivity‐based model updating approach. A sensitivity equation that diminishes adverse effects of incompleteness of FRF data is proposed for model updating. Efficiency of the proposed method and impacts of measurement errors and incompleteness of measured data are examined numerically through a truss reference example. The stiffness and mass parameters of the intact model are updated using the damped FRFs of the simulated damaged model. The results demonstrate that the proposed method is capable of precisely identifying the location and the severity of damage in all studied cases. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-14T09:47:44.800343-05:
      DOI: 10.1002/stc.1768
  • Hybrid two‐step method of damage detection for plate‐like
    • Abstract: This paper develops a two‐step approach for structural damage detection. In the first step, the two‐dimensional generalized local entropy (2D‐GLE) is proposed to identify the damage location and number for plates. Based on the 2D‐GLE, singularities in plates are revealed with the aid of mode shapes; hence, damages are localized, and the number of which is estimated. Besides, the statistical analysis is applied in the analysis of 2D‐GLE damage maps to overcome the difficulty in damage detection methods without baseline data. In the second step, the damage severities at the identified locations are evaluated via the optimization using artificial bee colony (ABC) with the designed frequency object function. The advantages of the present method are as follows: (1) No‐baseline in the measurement of mode shapes. Damage localization via the 2D‐GLE avoids using healthy mode shapes serving as baselines in damage detection, and then only damaged mode shapes are required. (2) No down‐sampling. Compared with the wavelet‐based methods, no down‐sampling enhances the algorithmic robustness and accuracy. (3) Efficiency. This hybrid two‐step method shrinks the solving parameter domain sharply in optimization via the first step. Hence, only the severity parameters need to be investigated in ABC. (4) Robustness. ABC ensures the robustness of the proposed method. Different damage cases are investigated in simulations, single‐damage/multiple‐damage cases, and noise immunity tests demonstrate that the proposed method is effective and accurate in damage detection. At last, a simple experiment is given to verify the present algorithm. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-03T01:23:13.385038-05:
      DOI: 10.1002/stc.1769
  • Performance improvement method of support vector machine‐based model
           monitoring dam safety
    • Authors: Huaizhi Su; Zhexin Chen, Zhiping Wen
      Abstract: Under the comprehensive influence of material and loads, dam structural behavior presents the time‐varying nonlinear characteristics. To forecast the dam structural behavior (displacement, stress, seepage, etc.), the models monitoring dam safety are often built according to the prototype observations on dam safety. However, the modeling process is usually fulfilled with the offline and static pattern. As time goes on, the fitting and forecasting ability of built static model will decline gradually. The article is focused on the support vector machine (SVM)‐based model monitoring dam safety. The methods are studied to advance the adaptability of SVM model and reduce the modeling time. By implementing the impact analysis for SVM parameters and input vector, the optimization method of SVM parameters and input vector is presented to enhance the efficiency of building the SVM‐based static model monitoring dam safety. To describe dynamically the time‐varying mapping relationship between dam structural behavior (effect‐quantity) and its cause (influence‐quantity), the way is developed to update in real time above model by making the most use of new observations. The displacement of one actual dam is taken as an example to verify the modeling efficiency and forecasting ability. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-29T02:26:52.134791-05:
      DOI: 10.1002/stc.1767
  • Fatigue sensor for structural health monitoring: Design, fabrication and
           experimental testing of a prototype sensor
    • Authors: Subash Gokanakonda; Muralidhar K. Ghantasala, Daniel Kujawski
      Abstract: Fatigue damage monitoring of any structure is a prerequisite for reliable and effective structural health prognosis. A novel fatigue sensor for detecting and monitoring the fatigue damage and estimating the remaining life of machine components and structures subjected to cyclic loads is discussed. The fatigue sensor consists of alternate slots and strips having different strain magnification factors with respect to the nominal strain at the location where it is placed on the structure. The sensor experiences the strains which closely resemble the actual strain distribution in the critical area of the component. The sensor can be placed away from the notch‐root stress concentration region at a convenient location on the structure but would still experience the same fatigue damage as the notch‐root. The strips fail in a sequential manner from the strip experiencing the highest strain magnification to the lowest. Each strip failure corresponds to the particular fatigue damage accumulated by the structure being diagnosed. This information allows for predicting remaining component life. The design of the fatigue sensor is validated by the elastic and elastic‐plastic finite element analysis simulations. The finite element analysis (FEA) simulations were performed in 2D and 3D configurations. This paper describes different aspects of the fatigue sensor design, analytical modeling, FEA simulation, fabrication, and experimental testing along with the results. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-19T01:24:16.826451-05:
      DOI: 10.1002/stc.1765
  • An improved substructural damage detection approach of shear structure
           based on ARMAX model residual
    • Authors: Liu Mei; Akira Mita, Jin Zhou
      Abstract: In this paper, an improved substructure‐based damage detection approach is proposed to locate and quantify damages in a shear structure, which extends from a previously established substructure approach. This method requires only three sensors to locate and quantify the damage in any story of a shear structure building. Similarly, as in the previous approach, a substructure approach is adopted in the improved procedure to divide a complete structure into several substructures. To improve the noise immunity and damage detection robustness under different types of excitations and realistic conditions, this paper proposes an autoregressive‐moving average with exogenous inputs (ARMAX) model residual‐based technique to correct the former damage indicator. The correction coefficient is defined as the normalized Kolmogorov–Smirnov (KS) test statistical distance between the two distinguished data sets of ARMAX model residual generalized from input–output data process for undamaged and damaged states. To better assess the performance of the improved procedure, simulation and experimental verifications of the proposed approach have been conducted, and the results are compared with the previous method. It shows that the improved procedure works much better and more stable than the previous method especially when it is applied to realistic problems. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-16T02:55:29.803503-05:
      DOI: 10.1002/stc.1766
  • Impact damage identification in composite skin‐stiffener structures
           based on modal curvatures
    • Abstract: The feasibility of a vibration‐based damage identification approach for impact damage in two advanced composite skin‐stiffener structures is investigated in this paper. Mode shape curvatures combined with the modal strain energy damage index (MSE‐DI) algorithm are utilized to identify the damage. Special attention is paid to the effective application of this vibration‐based methodology by investigating the relation between the damage location, the structural design, and the dynamic behavior. The performance of a 1D and 2D formulation of the MSE‐DI algorithm is compared for several damage scenarios. Experiments demonstrated the capabilities of the MSE‐DI algorithm to detect, localize, and roughly quantify the size of barely visible impact damage in advanced composite structures. It is concluded that the method is particularly effective for health monitoring of skin‐stiffener connections. The most effective results were obtained by considering the 1D formulation in the direction of the stiffeners for the stiffener mid‐section and perpendicular to the stiffeners for the stiffener run‐out. The method remained inconclusive in the case of pure skin‐related damage. The results obtained in this study contribute to the development of guidelines for vibration‐based structural health monitoring of advanced composite skin‐stiffener structures. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-08T01:39:50.995135-05:
      DOI: 10.1002/stc.1754
  • A degree of dispersion‐based damage localization method
    • Abstract: We present an efficient and robust damage localization method. Its applications therefore include defect location in shear buildings and beam structures. The proposed method is based on the knowledge of the difference of curvatures, computed for a structure before and after damage occurs. However, instead of using modal shapes for this purpose, as is frequently performed, the present method computes the curvature directly from acceleration signals, without identifying modal shapes of the structure. Additionally, the accelerations are subjected to averaging, which reduces measurement noise, and logarithm extraction, which renders the method independent of the amplitude of the loading impulse used for damage location. Another important feature of the method is that it does not require any calibration of numerical models, because it is solely based on measurement data. The presented method of damage location is illustrated with two examples, which involve experimental tests on laboratory‐scale structures. The first example concerns defect location in a shear‐building structure, and the second one in a spatially excited simply supported steel beam. Both cases confirm the effectiveness of the method, and its robustness to measurement noise. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-04T21:52:20.000873-05:
      DOI: 10.1002/stc.1760
  • Unscented Kalman filter with unknown input and weighted global iteration
           for health assessment of large structural systems
    • Abstract: A novel concept denoted as unscented Kalman filter with unknown input and weighted global iterations (UKF‐UI‐WGI) to assess health of large structural systems is proposed. It incorporates the basic features of UKF to identify systems in the presence of severe nonlinearity but then added a few desirable features to increase its implementation potential. Because the information on excitation and unknown initial state vector is necessary to implement any UKF‐based approach, a substructure concept is introduced to generate them. The traditional UKF concept attempts to identify small structural systems using large duration of response histories in one global iteration. Because it fails to assess the defective states of large structures in most cases, a weighted multiple global iterations procedure with objective functions using short duration responses is introduced. The superiority of UKF‐UI‐WGI over the traditional UKF is demonstrated with the help of several illustrative examples using single and multiple substructures in identifying both defect‐free and defective states. With the help of the same examples, the superiority of the proposed method over the extended Kalman filter‐based method developed by the team earlier is conclusively documented. With the help of parametric studies, it is documented that the proposed method is robust, accurate, and stable. The study confirms that UKF‐UI‐WGI can identify large structural system using only limited response information measured at a small part of a structure without using any excitation information. The concept significantly advances the state‐of‐the‐art in UKF‐based nonlinear system identification and considerably improves its implementation potential. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-04T20:56:39.419163-05:
      DOI: 10.1002/stc.1764
  • Sparse l1 optimization‐based identification approach for the
           distribution of moving heavy vehicle loads on cable‐stayed bridges
    • Authors: Yuequan Bao; Hui Li, Zhicheng Chen, Fujian Zhang, Anxin Guo
      Abstract: A method for identifying the distribution of moving heavy vehicle loads is proposed for cable‐stayed bridges based on a sparse l1 optimization technique. This method is inspired by the recently developed compressive sensing (CS) theory, which is a technique for obtaining sparse signal representations for underdetermined linear measurement equations. In this study, sparse l1 optimization is employed to localize the moving heavy vehicle loads of cable‐stayed bridges through cable force measurements. First, a simplified equivalent load of vehicles on cable‐stayed bridges is presented. Then, the relationship between the cable forces and the moving heavy vehicle loads is established based on the influence lines. With the hypothesis of a sparse distribution of vehicle loads on the bridge deck (which is practical for long‐span bridges), moving heavy vehicle loads are identified by minimizing the ‘l2‐norm'of the difference between the observed and simulated cable forces caused by the moving vehicles penalized by the ‘l1‐norm’ of the moving heavy vehicle load vector. A numerical example of an actual cable‐stayed bridge is employed to verify the proposed method. The robustness and accuracy of this identification approach (with measurement noise for multi‐vehicle spatial localization) are validated. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-04T00:52:50.42359-05:0
      DOI: 10.1002/stc.1763
  • The hybrid multivariate analysis method for damage detection
    • Abstract: As the defects and superiorities of indices are mutualisms frequently, such as noise immunity and damage sensitivity, damage identification based on single damage index may hardly present the effective result all the time, so multiple indices fusion method is introduced in this paper to achieve some complementary improvements. In this paper, two kinds of no‐baseline mode shape‐based damage indices, namely, the generalized local entropy and the curvature waveform capacity fractural, are utilized to construct the basic index set for combination, and the fuzzy cluster method is introduced in order to establish fusion process. These two parts generate the hybrid multivariate analysis method finally. The multivariate analysis' superiority mainly displays on two aspects: (1) the use of no‐baseline mode shape‐based method ensures the damage detection efficiency with the absence of healthy mode shape serving as baseline and (2) the fusion conducted by cluster method provides the mutual support and complementation among indices, which can enhance the robustness of algorithm. The performances of the present method are verified via sufficient numerical examples, and then experiments are demonstrated on three typical engineering structures, namely, cantilever beam, blower wheel, and rotor, for further validations. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-02T00:57:11.055756-05:
      DOI: 10.1002/stc.1758
  • Friction estimation in wind turbine blade bearings
    • Abstract: The influence of friction on wind turbines (WTs) is often seen as undesirable as it has been proven to be the root cause of different severe damages, where the most vulnerable WT's components are bearings. Accurate modelling and identification of friction affects are thus required in order to characterise frictional behaviour and prevent severe damages. This paper addresses the problem on the real‐time estimation of friction levels that vary in time with different rates in the WT's blade bearings. Because of ageing or damage progression in bearings, friction parameters change in time. Knowing the material properties and a damage model, monitoring of the friction can be used for condition monitoring of WT's blade bearings. The considered nonlinear identification methods suitable for estimation of fast varying parameters are the extended Kalman filter (EKF), the unscented Kalman filter, the particle filter (PF) and the PF combined with the EKF. This paper also proposes a novel modification of a differential evolution algorithm for the identification of parameters that slowly vary in time. The main contribution of this paper is the algorithm, which combines the modified differential evolution algorithm with optimal nonlinear filters for the estimation of parameters which vary at different rates. A LuGre friction model and a realistic WT sensor setup are selected. The techniques are benchmarked against simulated WT data, and their performances are compared and discussed. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-01T02:26:07.202124-05:
      DOI: 10.1002/stc.1752
  • Modal identification of damaged frames
    • Authors: Mariella Diaferio; Vincenzo Sepe
      Abstract: The paper investigates the possibility of identifying localised damages for multi‐span and multi‐floor linear elastic frames using only natural frequencies measured in the undamaged and damaged configurations. Namely, frames of increasing complexity are studied by exploring one by one their significant substructures (i.e. multi‐span beams, floor by floor); the error function is defined and minimised on a database of finite element damaged models that only includes the natural frequencies of the local modes of the substructure, that is, the only modes significantly affected by the localised damage considered here. The performances and limits of the procedure are here discussed by means of numerical simulations on steel frames of increasing complexity; a particular attention is also devoted to the role of noise on the identification procedure. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-29T11:22:34.482893-05:
      DOI: 10.1002/stc.1762
  • Structural health monitoring of a damaged church: design of an integrated
           platform of electronic instrumentation, data acquisition and client/server
    • Abstract: A practical view is provided on the integration of electronic instrumentation, data acquisition, and software development systems applied to the analysis of pathological structural processes. This system will enable researchers to remotely monitor constructions; compile a register of historical data, creating files for postprocessing; and establish computer‐based protocols for evaluation of information, defining automatic alarms when the monitored data exceed preset limit values. This integration is based on the implementation of a remote terminal unit architecture in an industrial PC along with some other elements, namely, the following: suitable data acquisition cards for the type of sensors used, which continuously collect the data the sensors gather; the installation of an application server that periodically communicates with the system, extracting data while guaranteeing persistence; and finally, a web server, which provides remote access to both the data themselves and the system configuration, using a client application developed in JavaFX, a platform for developing rich Internet applications. As an example of the integration, the architecture of a system deployed in a Church in Comillas, Spain, is shown. The work carried out related to the register of existing damage is reported in order to explain the choice of the zones for deployment of the monitoring devices as well as the tasks involved in the installation of the sensors and other devices. Finally, the evolution is presented of the measurements taken during more than 1.5 years of monitoring, as well as their validation through comparison with those obtained by discrete in situ measurement. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-26T01:03:09.644758-05:
      DOI: 10.1002/stc.1759
  • Damage detection of SFRC concrete beams subjected to pure torsion by
           integrating acoustic emission and Weibull damage function
    • Authors: Arash Behnia; Hwa K. Chai, Navid Ranjbar, Mohd Z. Jumaat
      Abstract: In some cases, torsion is the dominant or critical factor contributing to the failure of a concrete member. This research proposes a novel damage detection method for fiber‐reinforced concrete beams subjected to pure torsion loading by statistical analysis of acoustic emission (AE) data. Concrete beams with varying water/cement ratios and different fiber volume fractions were subjected to pure torsion during AE monitoring. It was found that the cumulative AE event with respect to the twist angle correlated well to the mechanical loading. A Weibull rupture probability distribution is introduced to quantitatively predict the mechanical damage behavior under pure torsion. A bi‐logarithmic regression analysis is carried out to calibrate the Weibull damage distribution function with the detected AE data in order to characterize the torsion fracture process. Moreover, a quantitative approach by means of b‐value results is presented in this article to further analyze damage and fracture process. Torsion fracture properties were correlated to the AE parameters, and it was shown that the magnitudes of AE parameters were influenced significantly by mechanical properties of specimens. Therefore, AE would be suitable to describe the fracture of concrete specimens subjected to torsion. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-26T01:00:14.28364-05:0
      DOI: 10.1002/stc.1753
  • Vision‐based algorithms for damage detection and localization in
           structural health monitoring
    • Authors: Ziemowit Dworakowski; Piotr Kohut, Alberto Gallina, Krzysztof Holak, Tadeusz Uhl
      Abstract: Deflection curve can be used to detect and localize damage in civil engineering structures. In this paper, a vision‐based method applied for in‐plane displacement field measurement of cantilever beams is presented. The deflection curve of the analyzed structure is computed by means of the digital image correlation. Damage is introduced into the structure. Resulting deflection curves are used as an input to the novel damage detection algorithms: line segments method and voting method. The algorithms are then compared with the second derivative method and assessed through the probability of detection procedure. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-26T00:59:18.360237-05:
      DOI: 10.1002/stc.1755
  • Benchmark problem in active structural control with wireless sensor
    • Authors: Zhuoxiong Sun; Bo Li, Shirley J. Dyke, Chenyang Lu, Lauren Linderman
      Abstract: Structural control systems offer an attractive approach to protect civil infrastructures from natural hazards such as earthquakes. Wireless structural control systems that utilize wireless sensors for sensing, communication, and control have drawn increased attention because of the flexible installation, rapid deployment, and reduced cost. Although there are studies of wireless control systems for civil structures, a benchmark problem that captures not only the dynamics of the plant but also the realistic features of a wireless network has not been available. In this paper, a benchmark model for an active mass driver system with a wireless sensor network is presented. This wireless control benchmark model combines a seismically excited building benchmark model developed with Simulink (Matlab, MathWorks, Inc., Natick, MA, USA) and a wireless sensor network implemented in simulation using a state‐of‐the‐art wireless simulator TOSSIM (UC Berkeley, Berkeley, CA, USA). Wireless signal and noise traces collected from a real‐world multistory building are used as inputs to TOSSIM to realistically simulate the wireless sensor network. Wireless control design issues such as network‐induced delay, data loss, available sensor measurements, measurement noises, and control constraints can be studied with this benchmark model. A sample controller is provided to illustrate the wireless control design. Evaluation criteria have been provided to examine resources and control performances. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-23T09:01:27.256493-05:
      DOI: 10.1002/stc.1761
  • A lower bound for the variance of frequency and damping ratio identified
           from noisy vibration measurements
    • Abstract: This paper derives exact expressions to compute the lowest achievable variance by any unbiased estimator of modal frequency and damping ratio from free vibration and forced vibration signals contaminated by additive zero‐mean Gaussian white noise. These limits are found through the Cramer–Rao lower bound theory. The paper presents simulated system identification results that confirm the applicability of the derived expressions. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-23T09:00:18.6706-05:00
      DOI: 10.1002/stc.1757
  • An inverse parallel genetic algorithm for the identification of skin/core
           debonding in honeycomb aluminium panels
    • Authors: V. Meruane; V. Fierro
      Abstract: Honeycomb sandwich structures are used in a wide variety of applications. Nevertheless, because of manufacturing defects or impact loads, these structures can experience imperfect bonding or debonding between the skin and the honeycomb core. Instances of debonding reduce the bending stiffness of the composite panel, which causes detectable changes in its vibration characteristics. This article presents a new methodology to identify debonded regions in aluminium honeycomb panels that uses an inverse algorithm based on parallel genetic algorithms. The honeycomb panels are modelled with finite elements using a simplified three‐layer shell model. The adhesive layer between the skin and core is modelled using linear springs, with reduced rigidity for the debonded sectors. The algorithm is validated using experimental data from an aluminium honeycomb panel containing different damage scenarios. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-18T03:26:30.546239-05:
      DOI: 10.1002/stc.1756
  • Deflection monitoring and assessment for a suspension bridge using a
           connected pipe system: a case study in China
    • Authors: Yang Liu; Yang Deng, C. S. Cai
      Abstract: This paper discusses the application of a connected pipe system (CPS) to a suspension bridge in China for the purpose of vertical deflection monitoring and assessment. The CPS mainly consists of three main parts: the pressure transmitters to detect the height change of liquid, the pipes to connect the reference point and measurement points, and the liquid to fill the connected pipes. Multiple pressure transmitters, taken as the measurement point, were mounted inside of the girder. A reference transmitter was mounted inside of a tower, taken as a fixed point. To verify the performance and reliability of the CPS, a controlled load test after the completion of the bridge construction and an uncontrolled load test under the actual traffic loading were carried out. The results showed that the CPS exhibited excellent capability in real‐time measurement of vertical deflection of the suspension bridge. With the long‐term deflection data monitored by the CPS, the extreme deflections with respect to vehicle loads were predicted by extreme value analysis. The generalized extreme value distribution was adopted to establish the probability models of the daily maximum and minimum deflection sequences, and then the extreme deflections within the design reference period of 100 years were determined based on the probability models. Comparison of the extreme deflections and the deflection thresholds was carried out. The deflection monitoring and assessment method proposed in this paper have shown high potential of applicability in the practice of health monitoring for long‐span bridges. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-12T23:43:05.950906-05:
      DOI: 10.1002/stc.1751
  • Bridge damage detection using ambient traffic and moving force
    • Authors: Eugene OBrien; Ciaran Carey, Jennifer Keenahan
      Abstract: This paper investigates a novel method for damage detection using a moving force identification algorithm. The method aims to detect the changes in the predicted forces applied by vehicles crossing a bridge, which are shown to be sensitive to damage. A two‐dimensional vehicle–bridge interaction model is used in theoretical simulations to assess the effectiveness of the method in detecting changes in stiffness. Fleets of similar vehicles are simulated, and the force pattern of greatest frequency is used as the damage indicator. Results indicate that the method is more sensitive to damage than direct measurements of displacement and can detect a loss in stiffness due to a crack with a depth of as little as 6% of the beam depth. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-04-27T04:51:00.099933-05:
      DOI: 10.1002/stc.1749
  • Robust force tracking control scheme for MR dampers
    • Authors: Felix Weber
      Abstract: This paper describes a novel force tracking control scheme for magnetorheological (MR) dampers. The feed forward, which is derived by a control‐oriented mapping approach to reduce modelling effort of the inverse MR damper behaviour, compensates for the main steady‐state nonlinearity of the MR damper force and thereby linearizes the plant. The resulting force tracking error due to model imperfections and parameter uncertainties is reduced by parallel proportional and integral feedback gains that are formulated based on the absolute values of actual MR damper force and desired control force due to the semi‐active constraint of the MR damper force. The feedback is enriched by an anti‐reset windup to account for MR damper current constraints and the concept of current reversal to accelerate demagnetization. The experimental validations of the force tracking control scheme on a rotational and a long‐stroke MR damper demonstrate its robustness and efficacy. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-04-14T00:58:23.226712-05:
      DOI: 10.1002/stc.1750
  • An electromagnetic vibration absorber with harvesting and tuning
    • Abstract: This paper describes the development of an electromagnetic vibration absorber (EVA) with energy recovery and frequency tuning control capabilities. The essential component of the EVA is an electromagnetic transducer, interfacing between electrical and mechanical domains, connected to an external electrical circuit. So far, the use of electromagnetic devices in vibration‐control applications has been driven by energy‐harvesting applications. In these works, the electromagnetic transducer acts as a damper in the mechanical domain by connecting a resistance across the terminals of the device. By emulating the resistive components, some of the power that would have been dissipated in the resistor can be converted into usable power. The use of electromagnetic devices also opens the door (i) to the synthesis of more complex networks in the electrical domain, most of them impractical or too complicated to be synthesized mechanically and (ii) to the development of frequency tuning networks. We consider the possibility of using an EVA along with a resistance emulator to give a self‐powered adaptive EVA. We explore the switching in of different elements across the terminals of the electromagnetic transducer in order to be able to derive new low‐powered control schemes for better vibration absorption. With the underlying goal to develop high performance, energy‐efficient vibration‐control devices, a small scale EVA device was tested, coupled with a virtual host structure. The results presented here demonstrate the potential for self‐tuning of such a device. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-04-07T04:11:32.246912-05:
      DOI: 10.1002/stc.1748
  • Investigation of fatigue performance of welded details in long‐span
           steel bridges using long‐term monitoring strain data
    • Abstract: Monitoring strain data provides possibilities for the fatigue assessment of the critical components in real structures under the operational conditions. This paper presents a case study on the investigation of fatigue performance of welded details. Long‐term monitoring strain data of 4 years between 2006 and 2009 collected by the structural health monitoring system mounted on the Runyang Suspension Bridge and Runyang Cable‐stayed Bridge are utilized. The study focuses on two aspects: (i) the effects of different strain components in the raw strain data on the fatigue damage assessment and (ii) the necessity of long‐term strain measurement for fatigue evaluation. The results indicate that temperature effect on the stress range spectrum is negligible. The enormous low‐level stress cycles caused by random interference would result in erroneous equivalent stress ranges and number of cycles, and thus should be eliminated from the stress range spectrum. Through in‐depth analysis of monitoring strain data in three special months and in 3 years, respectively, it is revealed that short‐term data monitored in a few days and medium‐term data monitored in a few months are not adequate enough to reveal the actual fatigue behaviors of steel bridges and would give inaccurate fatigue life prediction. Finally, the fatigue life predictions of two types of welded details by considering traffic flow growth are carried out. Lessons learned from the long‐term monitoring are expected to enhance our understanding in fatigue performances of steel bridges. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-26T23:22:11.036488-05:
      DOI: 10.1002/stc.1747
  • Tuned liquid column ball damper for seismic vibration control
    • Authors: Sourav Gur; Koushik Roy, Sudib Kumar Mishra
      Abstract: Tuned liquid column damper (TLCD) is a passive control device for vibration control of structures. Recently, the tuned liquid column ball damper (TLCBD) has been introduced for performance enhancement over the original TLCD. In this paper, the efficiency of the TLCBD is assessed under random earthquake events. The response of a single‐degree‐of‐freedom system with TLCBD is evaluated by stochastic analysis and compared with the TLCD. The study reveals significantly improved performance of TLCBD over TLCD in terms of reducing response of the structure as well as the liquid column. The performance largely hinges on the optimum tuning ratio and the ball‐to‐tube diameter ratio values, which are proposed herein. The parametric studies establish the performance robustness of the TLCBD under loading and parametric variations. Furthermore, the accuracy of the optimal stochastic responses is verified through deterministic response analysis under recorded seismic motions. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-26T23:03:53.40662-05:0
      DOI: 10.1002/stc.1740
  • Elimination of torsion and pounding of isolated asymmetric structures
           under near‐fault ground motions
    • Authors: Mohammed Ismail
      Abstract: This paper aims at forcing the isolated asymmetric structures to behave as symmetric structures with, theoretically, no absolute torsional responses. In addition, it attempts to provide efficient protection to such structures against severe near‐fault ground motions considering limited seismic gaps with no seismic pounding. To achieve these goals, the recently proposed multi‐feature roll‐in‐cage (RNC) isolator is used. An improved full‐feature sap2000 model (Computers and Structures, Inc., Walnut Creek, CA, USA) is first developed for the RNC isolator then validated using analytical and experimental results. Next, an RNC isolation method that could eliminate the eccentricities between both structural centers of mass and rigidity is employed to theoretically remove structural torsion. It is based on using different isolator sets with unequal elastic stiffness to allow for shifting the center of rigidity at the isolation level, having dominant lateral behavior in case of isolated structures, to coincide with the structural center of mass above that level. After that, the ability of the RNC isolator to provide efficient seismic isolation considering relatively limited seismic gaps is investigated under unidirectional and bidirectional near‐fault earthquakes. This could be attained through the independent source of high hysteretic damping and pre‐yield elastic stiffness of the RNC isolator, in addition to its integrated self‐stopping or buffer mechanism. The obtained results demonstrate the capability of the RNC isolator to, theoretically, eliminate torsional responses of isolated asymmetric structures besides providing relatively efficient seismic isolation, with no seismic pounding, considering insufficient or limited seismic gaps under severe near‐fault unidirectional and simultaneous bidirectional ground motions. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-24T00:44:08.518601-05:
      DOI: 10.1002/stc.1746
  • Investigation of fiber Bragg grating strain sensor in dynamic tests of
           small‐scale dam model
    • Authors: Shuli Fan; Liang Ren, Jianyun Chen
      Abstract: For the low strength of model material, it is difficult to test the deformation of the small‐scale dam model during shaking table tests. Based on the principle friction, a type of fiber Bragg grating (FBG) strain sensor with enhanced strain sensitivity was developed to measure the strain of low‐strength material. The principle of the small‐scale FBG strain sensor and its characteristics of strain transferring were discussed using a calibration test. Dynamic strain and residual strain of dam model were measured using FBG strain sensors embedded in models and compared with data calculated by numerical analysis. The results demonstrate that this type of FBG strain sensor shows advantages of high sensitivity, ease for installation, and high reliability. FBG sensors adhere to model material completely. The strains measured from FBG sensors are agreed with the results calculated by numerical simulation. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-24T00:28:42.47323-05:0
      DOI: 10.1002/stc.1745
  • Structural model updating of an in‐service bridge using dynamic data
    • Abstract: Recent developments in instrumentation, modeling, and data collection have advanced the state of the art in structural health monitoring in many engineering areas. However, the application of these developments in civil engineering infrastructure still presents some challenges. With approximately 11% of the bridges in the USA classified as structural deficient and billions of dollars required for either replacement or rehabilitation, transportation authorities require more efficient methods for condition assessment of existing bridges and funding allocation. In this article, a frequency response function‐based, two‐step model updating technique is applied to the Powder Mill Bridge. The Powder Mill Bridge is a typical overpass bridge constructed in 2009 and located in the town of Barre, Massachusetts. The goal of this research is to obtain a baseline finite element model that captures the bridge's behavior in its healthy condition using experimentally collected data from testing performed in 2010. The proposed two‐step protocol successfully identified stiffness, mass, and damping parameters in simulated scenarios with contamination from measurement errors. Likewise, experimental validation using field collected dynamic data produced parameters that were reflective of the field‐observed structural condition of the tested bridge. If the model updating protocol is repeated using collected data at standard intervals, the baseline could be eventually used to identify changes in structural parameters that are indicative of damage. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-19T04:47:53.822413-05:
      DOI: 10.1002/stc.1742
  • Data‐based structural health monitoring using small training data
    • Authors: Luciana Balsamo; Raimondo Betti
      Abstract: One of the most efficient ways to solve the damage detection problem using the statistical pattern recognition approach is that of exploiting the methods of outlier analysis. Cast within the pattern recognition framework, damage detection assesses whether the patterns of the damage‐sensitive features extracted from the response of the system under unknown conditions depart from those drawn by the features extracted from the response of the system in a healthy state. The metric dominantly used to measure the testing feature's departure from the trained model is the Mahalanobis Squared Distance (MSD). Evaluation of the MSD requires the use of the inverse of the training population's covariance matrix. It is known that when the feature dimensions are comparable with the number of observations, the covariance matrix is ill‐conditioned and numerically problematic to invert. When the number of observations is smaller than the feature dimensions, the covariance matrix is not even invertible. In this paper, four alternatives to the canonical damage detection procedure are investigated to address this issue: data compression through discrete cosine transform, use of pseudo‐inverse of the covariance matrix, use of shrinkage estimate of the covariance matrix, and a combination of the three aforementioned techniques. The performance of the four methods is first studied on simulated data and then compared using the experimental data recorded on a four‐story steel frame excited at the base by means of a shaking table available at the Carleton Laboratory at Columbia University. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-19T04:41:59.712141-05:
      DOI: 10.1002/stc.1744
  • A finite‐element based damage detection technique for nonlinear
           reinforced concrete structures
    • Abstract: Civil engineering structures, such as reinforced concrete frames, exhibit nonlinear behavior when subject to dynamic loads, such as earthquakes. The ability to detect damages in structures after a major earthquake will ensure their reliability and safety. Innovative analysis techniques for damage detection of structures have been extensively studied recently. However, practical and effective local damage identification techniques remain to be developed for nonlinear structures, in particular hysteretic reinforced concrete (RC) structures. In this paper, a smooth hysteretic model with stiffness and strength degradations and with the pinching effect is used to represent the dynamic characteristics of RC frames. A system identification method capable of detecting damages in nonlinear structures, referred to as the adaptive quadratic sum‐square error with unknown inputs (AQSSE‐UI), will be used to detect damages in hysteretic RC frames. The performance of the AQSSE‐UI technique will be demonstrated by the experimental data. A one‐third‐scale two‐story RC frame has been tested experimentally on the shake table at National Center for Research on Earthquake Engineering, Taiwan. This two‐story RC frame was subject to different levels of ground excitations back to back. The RC frame is firstly considered as a time‐varying linear model with rotational springs at joints, and the tracking of the degradation of the time‐varying stiffness parameters is carried out using the AQSSE‐UI technique. Then the same RC frame is considered as a nonlinear structure consisting of plastic hinges at joints following a smooth hysteretic model. Experimental results show that the AQSSE‐UI technique is quite effective for tracking (i) the stiffness degradation of time‐varying linear structures and (ii) the nonlinear hysteretic parameters with stiffness and strength degradations as well as the pinching effect. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-03-13T01:33:17.511086-05:
      DOI: 10.1002/stc.1736
  • Damage detection in structures using a transmissibility‐based
           Mahalanobis distance
    • Abstract: In this paper, a damage‐detection approach using the Mahalanobis distance with structural forced dynamic response data, in the form of transmissibility, is proposed. Transmissibility, as a damage‐sensitive feature, varies in accordance with the damage level. Besides, Mahalanobis distance can distinguish the damaged structural state condition from the undamaged one by condensing the baseline data. For comparison reasons, the Mahalanobis distance results using transmissibility are compared with those using frequency response functions. The experiment results reveal quite a significant capacity for damage detection, and the comparison between the use of transmissibility and frequency response functions shows that, in both cases, the different damage scenarios could be well detected. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-27T03:51:56.089969-05:
      DOI: 10.1002/stc.1743
  • Novelty detection for SHM using raw acceleration measurements
    • Authors: Vinicius Alves; Alexandre Cury, Ney Roitman, Carlos Magluta, Christian Cremona
      Abstract: Structural health monitoring is a problem that can be addressed at many levels. One of the most promising approaches used in damage assessment problems is based on pattern recognition. The idea is to extract features from data that characterize only the normal condition and to use them as a template or reference. During structural monitoring, data are measured, and appropriate features are extracted as well as compared with the reference. Any significant deviations are considered as signal novelty or possible damage. Several studies present in the literature are based on the comparison of measured vibration data such as natural frequencies and vibration modes in undamaged and damaged states of the structure. This methodology has proven to be efficient; however, its application may not be the most adequate in cases where the engineer needs to know with certain imperativeness the condition of a given structure. This paper proposes a novelty detection approach where the concept of symbolic data analysis is used to manipulate raw vibration data (i.e., acceleration measurements). These quantities (transformed into symbolic data) are combined to three unsupervised classification techniques: hierarchy agglomerative, dynamic clouds and soft c‐means clustering. In order to attest the robustness of this approach, experimental tests are performed on a simply supported beam considering different damage scenarios. Moreover, this paper presents a study with tests conducted on a motorway bridge, in France, where thermal variation effects also play a major role. In summary, results obtained confirm the efficiency of the proposed methodology. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-27T02:17:29.907637-05:
      DOI: 10.1002/stc.1741
  • Free vibrations of a two‐cable network with near‐support
           dampers and a cross‐link
    • Authors: Haijun Zhou; Xia Yang, Limin Sun, Feng Xing
      Abstract: Vibration mitigation of cables is a crucial problem for cable‐supported bridges. A hybrid method for cable vibration mitigation that combines cross‐ties and dampers has been applied in engineering practice; however, the damping and frequency of this kind of system needs to be further assessed. In this paper, a system of two parallel cables with a cross‐link and dampers located near the cable anchorage is proposed and analyzed. Based on displacement continuity and force equilibrium at the damper and spring locations, the characteristic equation of the system is derived by applying the transfer matrix method. The complex characteristic equation is then numerically solved to obtain the modal damping and frequencies. The damping and frequency characteristics are discussed in detail for the case when the two cables are identical. Special attention is given to the case when only one damper is installed, and the approximate damping evaluation formulations are proposed when spring stiffness approaches infinity. Effects of mass–tension ratio, cable length ratio and frequency ratio on damping are also addressed. Finally, a case study of multimode damping optimization for bridge hangers is given. The results of this paper could be useful for vibration mitigation of two parallel cables and further development of design guidelines for cable networks with attached dampers. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-18T02:57:15.196647-05:
      DOI: 10.1002/stc.1738
  • Spatial H∞ approach to damage‐tolerant active control
    • Abstract: Damage‐tolerant active control is a new research area targeting to adapt fault‐tolerant control methods to mechanical structures submitted to damage. Active vibration control is a mature engineering area, using modern control methods to address structural issues that may result from excessive vibration. However, the subject of structural vibration control under damage represents a novel subject in the literature. There are some difficulties to adapt regular controller designs to active control, which may not result in good performance even for healthy structures. Fault detection and diagnosing research has conducted to the development of the fault‐tolerant control area, whose methods are equally hard to translate to damaged structure control. Spatial active vibration control encompasses some techniques that present important features to structure control; however, this is not necessarily true in the general control design area, where spatial constraints are normally not involved. In this paper, we propose an investigation of these spatial techniques, applied to structural damage control. Several new strategies for vibration control are presented and analyzed, aiming to attain specific objectives in damage control of mechanical structures. Finite element models are developed for a case study structure, considering healthy and three different damage conditions, which are used to design controllers, adopting an approach based on an H∞ spatial norm, and according to some of the proposed strategies. Discussion of the achieved results contributes to clarify the main concepts related to this new research area, and controller performance analysis permits to foresee successful real case application of the techniques here described. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-17T03:26:32.088281-05:
      DOI: 10.1002/stc.1729
  • Guided wave propagation in high‐speed train axle and damage
           detection based on wave mode conversion
    • Authors: Fucai Li; Xuewei Sun, Jianxi Qiu, Limin Zhou, Hongguang Li, Guang Meng
      Abstract: Axle is the main bearing part of the bogie system on a high‐speed train and is therefore requested on a higher reliability level. The high‐speed train axle is thick‐walled hollow cylindrical structure with variable cross section, which complicates ultrasonic guided wave propagation in the structure. Characteristics of the guided wave propagation in the train axle are systematically investigated in this study, so as to explore guided wave‐based structural health monitoring (SHM) method for this kind of structure. Piezoelectric patches are used as actuator to excite waves in the axle. Generated wave signals using single actuator and circumferential, limited number of actuator configurations are compared to optimize the transducer network. The longitudinal wave modes are therefore selected for damage detection of this kind of structure. Based on the analytical and finite element analysis (FEA), when the symmetric longitudinal wave modes meet defect, if have, in the train axle with variable cross section, mode conversion will happen and asymmetric flexural wave modes are therefore generated. Wave mode conversion‐based SHM technique is consequently proposed. The FEA results demonstrate the feasibility of guided wave‐based SHM technique for high‐speed train axle. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-17T01:02:21.826163-05:
      DOI: 10.1002/stc.1739
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