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ENERGY (183 journals)                 | Last

Showing 1 - 200 of 406 Journals sorted alphabetically
ActaEnergetica     Open Access  
Advances in Building Energy Research     Hybrid Journal   (Followers: 10)
Advances in Energy and Power     Open Access   (Followers: 5)
Advances in High Energy Physics     Open Access   (Followers: 21)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 28)
American Journal of Energy Research     Open Access   (Followers: 9)
Annals of Nuclear Energy     Hybrid Journal   (Followers: 6)
Annual Reports on NMR Spectroscopy     Full-text available via subscription   (Followers: 3)
Annual Review of Resource Economics     Full-text available via subscription   (Followers: 11)
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: 3)
Atomic Energy     Hybrid Journal   (Followers: 4)
Atoms for Peace: an International Journal     Hybrid Journal   (Followers: 3)
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: 39)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
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: 8)
Electrical and Power Engineering Frontier     Open Access   (Followers: 20)
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: 24)
Energy & Fuels     Full-text available via subscription   (Followers: 25)
Energy and Buildings     Hybrid Journal   (Followers: 10)
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: 17)
Energy Conversion and Management     Hybrid Journal   (Followers: 9)
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: 5)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 17)
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: 4)
Energy Research & Social Science     Full-text available via subscription   (Followers: 4)
Energy Science & Engineering     Open Access   (Followers: 3)
Energy Science and Technology     Open Access   (Followers: 12)
Energy Storage Materials     Full-text available via subscription  
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: 5)
Energy Technology & Policy     Open Access   (Followers: 2)
Energy, Sustainability and Society     Open Access   (Followers: 17)
Environmental Progress & Sustainable Energy     Hybrid Journal   (Followers: 6)
EPJ Photovoltaics     Open Access   (Followers: 3)
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: 5)
Functional Materials Letters     Hybrid Journal   (Followers: 1)
Gcb Bioenergy     Open Access   (Followers: 2)
Geomechanics for Energy and the Environment     Full-text available via subscription  
Geothermal Energy     Open Access   (Followers: 3)
Green     Hybrid Journal   (Followers: 1)
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: 3)
IEEE Power and Energy     Full-text available via subscription   (Followers: 24)
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: 26)
IET Power Electronics     Hybrid Journal   (Followers: 23)
Ingeniería Energética     Open Access  
Innovations : Technology, Governance, Globalization     Hybrid Journal   (Followers: 5)
International Journal of Alternative Propulsion     Hybrid Journal   (Followers: 6)
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: 9)
International Journal of Energy and Statistics     Hybrid Journal   (Followers: 1)
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: 5)
International Journal of Global Energy Issues     Hybrid Journal   (Followers: 8)
International Journal of Green Energy     Hybrid Journal   (Followers: 8)
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: 3)
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: 6)
Journal of China Coal Society     Open Access  
Journal of Energy     Open Access  
Journal of Energy & Natural Resources Law     Hybrid Journal   (Followers: 2)
Journal of Energy Chemistry     Full-text available via subscription   (Followers: 1)
Journal of Energy in Southern Africa     Open Access   (Followers: 2)
Journal of Energy Storage     Full-text available via subscription  
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: 28)
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: 5)
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   (Followers: 1)
Journal of Technology Innovations in Renewable Energy     Hybrid Journal  
Materials for Renewable and Sustainable Energy     Open Access   (Followers: 7)
Natural Resources     Open Access   (Followers: 2)
Nature Energy     Hybrid Journal   (Followers: 4)
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: 11)
Oil, Gas, Coal and Electricity - Quarterly Statistics - Electricite, charbon, gaz et petrole - Statistiques trimestrielles     Full-text available via subscription   (Followers: 9)
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: 28)
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   (Followers: 1)
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: 11)
Water International     Hybrid Journal   (Followers: 12)
Wiley Interdisciplinary Reviews : Energy and Environment     Hybrid Journal   (Followers: 5)
Wind Energy     Hybrid Journal   (Followers: 2)
Wind Engineering     Full-text available via subscription   (Followers: 2)

       | Last

Journal Cover Structural Control and Health Monitoring
  [SJR: 1.549]   [H-I: 35]   [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  [1612 journals]
  • Online structural damage identification technique using constrained dual
           extended Kalman filter
    • Authors: Subhamoy Sen; Baidurya Bhattacharya
      Abstract: Periodic health assessment of large civil engineering structures is an effective way to ensure safe performance all through their service lives. Dynamic response-based structural health assessment can only be performed under normal/ambient operating conditions. Existing Kalman filter-based parameter identification algorithms that consider parameters as the only states require the measurements to be sufficiently clean in order to achieve precise estimation. On the other hand, appending parameters in an extended state vector in order to jointly estimate states and parameters is reported to have convergence issues. In this article, a constrained version of the dual extended Kalman filtering (cDEKF) technique is employed in which two concurrent extended Kalman filters simultaneously filter the measurement response (as states) and estimate the elements of state transition matrix (as parameters). Constraints are placed on stiffness and damping parameters during the estimation of the gain matrix to ensure they remain within realistic bounds. The proposed method is compared against the existing Kalman filter-based parameter identification techniques on a three-degrees-of-freedom mass-spring-damper system adopting both unconstrained and constrained estimation approaches. cDEKF is then employed on a numerical six-story shear frame and a 3D space truss to validate its robustness and efficacy in identifying structural damage. The results suggest that cDEKF algorithm is an efficient online damage identification scheme that makes use of ambient vibration response.
      PubDate: 2016-11-23T23:00:31.056891-05:
      DOI: 10.1002/stc.1961
  • Health monitoring of rail structures using guided waves and
           three-dimensional diagnostic imaging
    • Authors: Chao Zhou; Chunliang Zhang, Zhongqing Su, Xia Yue, Jianhua Xiang, Guiyun Liu
      Abstract: With the rapid development of high-speed railway around the world, more advanced nondestructive evaluation (NDE) and structural health monitoring (SHM) techniques are required to detect structural damage in its forming stage before the damage jeopardizes the safety of the structures. In this aspect, guided-wave-based diagnostic imaging is a recent research focus, aimed at intuitionally showing the healthy status of the structure under inspection. However, the present diagnostic imaging techniques are mostly two-dimensional imaging methods, which fail to inspect complicated solid structures. In this study, a novel three-dimensional diagnostic imaging technique was developed in conjunction with an active sensor network, capable of real-time monitoring complex solid engineering structures. The ToF-based signal features were extracted from captured guided waves signals, and subsequently applied to define field values. The effectiveness of the approach was examined by identifying a crack introduced into a part of the real rail structure using both FE simulation and experiments. Results have revealed that the developed three-dimensional imaging approach is able to quantitatively visualizing structural damage in complicated solid engineering structures.
      PubDate: 2016-11-20T21:51:24.46578-05:0
      DOI: 10.1002/stc.1966
  • Optimization of an artificial neural network for fatigue damage
           identification using analysis of variance
    • Authors: Claudio Sbarufatti
      Abstract: Artificial neural networks (ANN) are extensively utilized in structural health monitoring. Nevertheless, the definition of a rigorous method for the optimization of their structure is still an unresolved issue, especially when applied to safety critical systems. In this paper, an approach typically adopted in the design of experiments and based on the analysis of variance (ANOVA) is used to statistically determine the number of hidden neurons in a three-layer ANN structure. Repeated trainings of the same network structure provide multiple observations of the performance index here, based on the root mean square error. Different levels of network structure complexity are statistically compared, based on the number of hidden nodes. ANOVA is used to determine whether there is statistical evidence that the network performance is influenced by the number of hidden nodes. This analysis allows defining the threshold number of hidden nodes above which there is no statistical evidence of a performance benefit by the increase of the ANN structure complexity. The method is applied to the optimization of a set of algorithms for the diagnosis of fatigue damage on a typical aeronautical structure, consisting of a metallic panel with a riveted skin-stringer construction. The ANNs for damage detection, localization, and quantification are trained and validated with finite element simulated strain data and are finally tested on experimental strain signals, acquired in real-time in a fatigue crack growth laboratory test program including a skin crack artificially initiated in a panel bay and two stringers that had failed naturally under fatigue load.
      PubDate: 2016-11-18T01:15:42.223166-05:
      DOI: 10.1002/stc.1964
  • Real-time hybrid simulation of the size effect of tuned liquid dampers
    • Authors: Fei Zhu; Jin-Ting Wang, Feng Jin, Li-Qiao Lu, Yao Gui, Meng-Xia Zhou
      Abstract: The use of tuned liquid dampers (TLDs) is an effective passive control technique to suppress structural vibration under wind and seismic loads. This paper investigates the size effect of TLDs on control efficiency. Given the advantages of real-time hybrid simulation, two issues affecting the control performance of TLD are addressed: (a) the geometric size and (b) the experimental model scale. A series of real-time hybrid simulations is performed, in which TLD devices with various sizes (including full-scale and small-scale) are experimentally modeled as physical substructures; the controlled structures are numerically simulated as numerical substructures. Results demonstrate that TLD performance is size dependent; a shallow liquid in TLD with lower relative liquid depth may be more efficient for both peak and root-mean-square response control. Scaled TLD models that are usually used in conventional shaking table tests generally overestimate the control performance of prototype TLD devices, indicating that full-scale TLD experiments should be pursued to ensure proper performance evaluation.
      PubDate: 2016-11-10T01:12:59.419872-05:
      DOI: 10.1002/stc.1962
  • Singular spectrum analysis combined with ARMAX model for structural damage
    • Authors: K. Lakshmi; A. Rama Mohan Rao, N. Gopalakrishnan
      Abstract: Time series analysis is being used popularly in structural health monitoring mainly because of its output-only and non-modal approach. Generally, the damage features are extracted either from the coefficients or the prediction errors of the time series models. However, when the incipient damage is small like minor cracks, the damage features of popularly used time series models, constructed using only the coefficients/prediction errors, are not sensitive. Therefore, identifying the presence or exact spatial damage location becomes difficult. In view of this, in this paper, we present an approach to enhance the sensitivity of the damage features by augmenting Singular Spectrum Analysis (SSA) to ARMAX model, enabling it to locate the smaller damage like cracks. The damage index is obtained from the Cepstral distance between any two ARMAX models. Numerical simulation studies have been carried out by considering an example of a simply supported beam girder with single and multiple cracks. Experimental studies on a simply supported RCC beam is conducted to demonstrate the effectiveness of the proposed algorithm. A benchmark problem associated with the bookshelf frame structure, proposed by Engineering Institute –Los Alamos National Laboratory, is used as another example for experimental verification of the proposed technique. SSA is found to improve the sensitivity of the damage features devised from the ARMAX models for detection of minor damage and damage localization on the structures.
      PubDate: 2016-11-08T03:10:14.278872-05:
      DOI: 10.1002/stc.1960
  • Optimal control of supersonic pre-twisted rotating functionally graded
           thin-walled blades
    • Authors: Mohammadreza Naghmehsanj; Behrooz Rahmani
      Abstract: In this paper, the optimal vibration control of a rotating, pre-twisted, single-celled box thin-walled beam made of functionally graded material is discussed. This beam is under aerothermoelastic loading and warping restraint. A first-order shear deformation theory enabling satisfaction of traction-free boundary conditions is employed to achieve governing dynamical model. These equations include the effects of the presetting angle, the secondary warping, temperature gradient through the wall thickness of the beam, and also the rotational speed. Moreover, quasi-steady aerodynamic pressure loadings are determined using first-order piston theory, and steady beam surface temperature is obtained from gas dynamics theory. The extended Galerkin method is then used to transform the blade partial differential equations into a set of ordinary differential equations. Transversely isotropic sensor-actuator piezoelectric pairs that are surface embedded along the blade are also considered for the purpose of closed-loop control. An optimal observer-based output feedback control scheme is used to stabilize the closed-loop system. Simulation studies demonstrate the effectiveness of the proposed method.
      PubDate: 2016-10-24T03:15:42.115671-05:
      DOI: 10.1002/stc.1957
  • Comparison of different statistical approaches for removing
           environmental/operational effects for massive data continuously collected
           from footbridges
    • Authors: Wei-Hua Hu; Álvaro Cunha, Elsa Caetano, Rolf.G. Rohrmann, Samir. Said, Jun Teng
      Abstract: The implementation of continuous dynamic monitoring systems in two bridges, in Portugal, is enabled to detect the occurrence of very significant environmental and operational effects on the modal properties of these bridges, based on automated processing of massive amounts of monitoring data collected by a set of accelerometers and thermal sensors over several years.In order to remove or mitigate such environmental/operational effects with the purpose of damage detection, two different statistical methods have been adopted. One of them is the multiple linear regression by performing nonlinear correlation analysis between measured modal properties and environmental/operational variables. Another one is principal component regression based on the identification of the linear subspace within the modal properties without using measured values of environmental and operational variables.This paper presents a comparison of the performance of these two alternative approaches on the basis of continuous monitoring data acquired from two instrumented bridges and simulated damage scenarios. It is observed that different methods show similar capacity in removing environmental effects, and the multiple linear regression method is slightly more sensitive to structural damage.
      PubDate: 2016-10-21T00:15:41.861053-05:
      DOI: 10.1002/stc.1955
  • Real-time structural monitoring of Building 350 at Del Valle University
    • Authors: Lisandro Arturo Jiménez-Roa; Johannio Marulanda-Casas, Alejandro Cruz-Escobar
      Abstract: Design errors, misuse, and natural or accidental events can cause small and cumulative damages or large and sudden damages that can deteriorate structural systems or cause their collapse. Structural monitoring consists in the permanent real-time tracking of information about the condition and performance of a structure. This paper presents the development, validation, and implementation of the structural monitoring system for building 350 at Del Valle University, located in Santiago de Cali, Colombia. The system uses the SSI and natural excitation technique with the eigensystem realization algorithm methodologies for modal identification and a specialized event-recognition algorithm based on the standard deviation analysis of vibrations. The dynamic behavior monitoring of the building has been conducted in real-time since January 2012, and six seismic events have been successfully recognized. The computational tool was validated using a finite element model with which the effect of variation in mass was evaluated.
      PubDate: 2016-10-18T02:11:02.437979-05:
      DOI: 10.1002/stc.1959
  • AOSID: An analytical solution to the output-only system identification
           problem to estimate physical parameters and unknown input simultaneously
    • Authors: Mostafa Ghobadi; Manoranjan Majji, Ehsan T. Esfahani
      Abstract: This paper studies an analytical solution for the identification problem of linear systems, where inputs are unknown and only output data are accessible. A linear output-only model (LOM) is developed and employed along with physical constraints in state space to simultaneously identify two subspace models, one of which represents the physical system and the other describes the behavior of the unknown input by reconstructing its history. Inputs are assumed to be an arbitrary combination of harmonic signals with constant or time varying exponential amplitudes with non-overlapping frequency ranges with natural frequencies of the physical system. The identification is first performed by a zero-input eigensystem realization algorithm in time domain that estimates the LOM in a generic form; we call it unfixed form, which contains both physical system model and input model in a coupled configuration. By transforming the LOM into a canonical form and utilizing the physical constraints, an analytical approach is developed to decouple the physical model from the input dynamics. The proposed method of analytical output-only system identification (AOSID) is evaluated through simulation of a set of scenarios to demonstrate its capabilities. To this end, we study the effects of type of sensor models, level of measurement noise, and complexity level of the problem on the estimation error. The accuracy of the identified LOM demonstrates that the AOSID method is capable of simultaneous identification of physical model and unknown inputs in the presence of measurement noise with a considerable accuracy at a modest computational expense. Furthermore, AOSID method demonstrates a considerable robustness against nonlinear inputs and white noise disturbances which challenge the assumptions initially made in the theoretical development of the model.
      PubDate: 2016-10-18T01:40:50.088738-05:
      DOI: 10.1002/stc.1951
  • Multi-scale model updating of a transmission tower structure using Kriging
    • Authors: F.Y. Wang; Y.L. Xu, S. Zhan
      Abstract: A multi-scale model is often constructed using different finite elements and consists of a global scale model for the structural system and a few local scale models for critical structural components so that the multi-scale simulation can concurrently exhibit both global performance and local behavior of the structure. To ensure the multi-scale model can best represent the real structure, multi-scale model updating technique shall be developed accordingly. This paper thus presents a multi-scale model updating method for a transmission tower structure using the Kriging meta-model that actually is a surrogate for the multi-scale model. Firstly, the multi-scale model of a transmission tower is established by using beam elements to simulate global structure and solid elements to simulate local joints with bolt connections. Secondly, the multi-objective optimization problem that involves multiple objective functions is established to update key parameters of the multi-scale model so that the errors between the measured and predicted structural dynamic characteristics and multi-scale responses can be minimized. To improve the computational efficiency and accuracy of optimization, the Kriging meta-method is used to find the updated key parameters of the tower after a comparison with other meta-methods is made. Finally, the proposed method is applied to a physical transmission tower model, which has been tested in a laboratory, to demonstrate the feasibility and accuracy of the proposed model-updating method. The updated results show that the proposed updating method can improve the accuracy of the multi-scale model of the tower in both global and local structural responses.
      PubDate: 2016-10-09T23:25:38.564386-05:
      DOI: 10.1002/stc.1952
  • Elastic-wave-based synthetic aperture focusing technique imaging system
           for detecting voids inside concrete structures
    • Authors: Jian-Hua Tong; Chin-Lung Chiu
      Abstract: In this paper, an elastic-wave-based imaging system was proposed for adopting synthetic aperture focusing technique to reveal the voids inside concrete structures. Design concept of each component in this system, including an impact source generator, a transducer, a signal capturing unit, and operation software, is clearly described. Relation between contact time and impact source selection was discussed and verified by an experiment of steel ball free-falling on a concrete specimen. A displacement transducer and corresponding signal capturing unit were carefully designed to get higher quality signals for Synthetic aperture focusing technique processing. A calibration experiment was conducted to ensure the capability of proposed point-source/point-receiver scheme for proper elastic wave generation and receiving. Besides, a concrete slab with an artificial defect was cast for experiment for usability evaluation. A 2D plane-stress finite difference simulation on corresponding numerical module was carried out for comparison. The experimental result shows good agreement with the numerical result not only on the B-scan diagram but also on the resultant image. It exhibits the potential of the proposed imaging system in inspecting defects of in-situ concrete structures by image.
      PubDate: 2016-10-06T02:40:45.55464-05:0
      DOI: 10.1002/stc.1956
  • Optimal placement of triaxial sensors for modal identification using
           hierarchic wolf algorithm
    • Authors: Ting-Hua Yi; Guang-Dong Zhou, Hong-Nan Li, Chuan-Wei Wang
      Abstract: Optimal triaxial sensor placement plays a crucial role in tridimensional modal identification; however, few studies have been conducted on this topic. In this paper, a holistic approach, including a tridimensional optimal criterion and solution method, is proposed for finding the optimal locations to deploy triaxial sensors. The tridimensional optimal criterion is established by combining the tridimensional modal assurance criterion and the redundancy function. The tridimensional modal assurance criterion is deduced from the one-dimensional modal assurance criterion by using the widely accepted Fisher information matrix, adopted to ensure the linear independence of identified tridimensional mode shapes. The redundancy function, which is defined by the similarity index among nodes, is developed to measure the information redundancy and to maintain effective visualization of the identified tridimensional mode shapes. To efficiently find the optimal triaxial sensor configuration with the proposed tridimensional optimal criterion, the hierarchic wolf algorithm (HWA) is developed by imitating the swarm intelligence embedded in the wolf pack. Five strategies, which are termed as coding and spreading wolves, searching behaviors, attacking behaviors, hierarchic population, and distributing food process, are employed to enhance the global searching ability of the HWA. The proposed approach is verified by a benchmark bridge model. The results indicate that the established tridimensional optimal criterion has the capability of ensuring optimal triaxial sensor configurations that make the identified tridimensional mode shapes have features of excellent linear independence and good visualization, and the HWA has strong ability and high efficiency in determining the global optimal triaxial sensor configuration.
      PubDate: 2016-10-06T02:36:35.040736-05:
      DOI: 10.1002/stc.1958
  • Structural damage identification via response reconstruction under unknown
    • Authors: C.D. Zhang; Y.L. Xu
      Abstract: The restriction of limited sensors for measurement acquisition and the presence of unknown excitation usually bring about more challenges in the vibration-based damage identification of large-scale civil structures. To explore the potential benefits of utilizing multitype dynamic responses and alleviate the necessity of deploying dense sensors and measuring excitations for structural damage identification, this study investigates a novelty damage identification method via response reconstruction when the external excitations acting on the structure are unknown. Response and excitation are reconstructed simultaneously through the implementation of Kalman filter under unknown input. Radial-basis-function network is employed to predict the mode shapes using modal properties extracted by experimental modal analysis after damage occurrence. The reconstructed response and excitation are finally integrated into to sensitivity based finite element model updating for localizing and quantifying the damage. A numerical simulation study is conducted on an overhanging steel beam under unknown excitation. The feasibility and effectiveness of the proposed method are further ascertained by laboratory tests of the beam.
      PubDate: 2016-10-04T23:15:36.473299-05:
      DOI: 10.1002/stc.1953
  • A pounding spacer damper and its application on transmission line
           subjected to fluctuating wind load
    • Authors: Xing Fu; Hong-Nan Li, Jia-Xiang Li, Peng Zhang
      Abstract: In this paper, a new pounding spacer damper (PSD) is proposed, and the control effect on the transmission line under the fluctuating wind load is validated. At first, the schematic of the proposed PSD is provided, and the mechanical models of elastic, damping, and pounding forces are then obtained. After that, the dynamic equations of transmission line equipped with the PSD are derived. On the basis, the finite element model of transmission line–PSD system with the ANSYS software is established, and the pounding force of the PSD is calculated and applied through the ANSYS Parametric Design Language. Then the response induced by the fluctuating wind load is simulated, and meanwhile, the control effects of the PSD and spacer damper without pounding force are compared, of which the results illustrate that the minimal reduction ratio for the conductor span can reach to 11.10%, indicating that the proposed PSD can effectively control the vibration of the conductor span under the fluctuating wind load. In addition, the parametric analysis of gap, frequency, and damping ratios is conducted and demonstrates that the gap and frequency ratio have great impact on the control effect while the influence of damping ratio is not very significant.
      PubDate: 2016-09-29T23:40:53.145074-05:
      DOI: 10.1002/stc.1950
  • Integrated distributed fiber optic sensing technology-based structural
           monitoring of the pound lock
    • Authors: Zhan-Pu Song; Dan Zhang, Bin Shi, Shen-En Chen, Meng-Fen Shen
      Abstract: In this paper, an integrated distributed fiber optic sensing technology, which includes Raman optical time-domain reflectometry (ROTDR), Brillouin optical time-domain analysis (BOTDA), and fiber Bragg grating (FBG) sensing technologies, is adopted to monitor the temperature and the stress/strain variations of a reinforced concrete pound lock structure during the construction process. The Raman optical time-domain reflectometry was used to monitor the internal temperature variation throughout the concrete curing process when concrete hydration heat was released in the base plate of the lock head. The FBG temperature sensors were adopted to measure the surface temperature of the concrete, and the temperature data were used to compensate the results that are measured by BOTDA sensing technology to get the real concrete strain of the base plate. To better understand the stress/strain state of the base plate before and after filling water in the lock, the BOTDA sensing cable and FBG temperature sensors monitoring continued throughout the whole construction process. The observation provided a positive indication that the proposed integrated distributed fiber optic sensing technology may have great potential in performance monitoring of hydraulic structures.
      PubDate: 2016-09-29T23:35:48.534607-05:
      DOI: 10.1002/stc.1954
  • Vibration-based bridge scour detection: A review
    • Authors: Ting Bao; Zhen Liu
      Abstract: Scour around bridge foundations is regarded as one of the predominant causes of bridge failures. Traditional methods primarily employ underwater instruments to detect bridge scour depths, which thus have difficulties in instrument installations and operations. The concept of scour detection derived from vibration-based damage detection has been explored in recent years to address such difficulties by investigating the natural frequency spectrum of a bridge or a bridge component. This paper presents a comprehensive review of existing studies on scour detection using the natural frequency spectrum of a bridge or a bridge component. Underlying mechanisms, laboratory and field tests, numerical studies, and data processing schemes are reviewed to summarize the state of the art, which are absent but urgently needed. Updates on recently developed scour monitoring sensors are also provided to complement the introduction. Based on the review, in-depth discussions in existing studies are made regarding a few controversial and unsolved issues to shed light on future research, highlighting issues such as the soil–structure interaction, locations of the sensor installation, and the influence of shapes of scour holes.
      PubDate: 2016-09-29T23:10:38.716567-05:
      DOI: 10.1002/stc.1937
  • Monitoring and time‐dependent analysis of vertical deformations of the
           tallest building in China
    • Authors: Qiusheng Li; Yinghou He, Hui Wang, Kang Zhou, Bowen Yan
      Abstract: Ping‐An Finance Center (PAFC) in Shenzhen, with a structural height of 597 m and a total height of 660 m, is currently the second tallest building in the world and the tallest in China. In this paper, based on the outputs of a structural health monitoring system installed in PAFC, a combined study of both on‐site measurements and numerical analysis of the vertical deformations (axial shortenings) of the super tall building during its various construction stages is carried out. It is worth noting that a novel strategy to adjust the elevation of each floor of PAFC was implemented in the design and construction of the super tall building, in which the floor‐to‐floor height is modestly increased to compensate for the axial shortenings of gravity load bearing elements during the construction process and in‐service stage. This design strategy is referred to as elevation reservation, and its effectiveness is verified through the field measurements of the vertical deformations in this study. A good agreement is found between the numerical results and the field measurements, which validates the finite element models of PAFC at different construction stages. The finite element models are further used to investigate the time‐dependent effects due to the construction sequence and the shrinkage and creep of concrete on the vertical deformations. The numerical results show that the vertical deformations would be seriously underestimated without consideration of the time‐dependent effects. The outcomes of this study would be of interest and practical use for engineers and researchers involved in the structural design, construction, and structural health monitoring of super tall buildings.
      PubDate: 2016-09-16T03:12:06.119661-05:
      DOI: 10.1002/stc.1936
  • Structural health assessment of historical timber structures combining
    • Authors: Mariapaola Riggio; Nicola Macchioni, Cristiano Riminesi
      Abstract: Examining the timber structure supporting the roof of Giotto's bell tower in Florence, this paper discusses the combination of non‐destructive (NDT), wave‐based methods for the characterization of timber structural elements. In particular, it analyses the on‐site applicability of selected wave‐based techniques for the identification of decay, damage, defects, and moist areas in structural timber. The applied NDT techniques are IR termography, microwave reflectometry, time‐of‐flight tomography, and mapping by means of elastic waves. Experimental results are compared with data obtained by means of consolidated NDT techniques, such as the electric resistance method for moisture content estimation and the drill‐resistance test for decay characterization. These can be considered non‐destructive, although they are invasive. The wave‐based NDT methods are found to be a value‐added complement to routine methodologies for a holistic diagnosis of timber members. Normal practice based on visual inspection, decay detection through point measurements of drill resistance, and moisture content estimation through local readings of electric resistance, can be substantially improved through full‐field, multi‐sensor, multi‐resolution imaging. Nevertheless, while the diverse NDT methods illustrated here can be useful for screening large areas in a completely non‐invasive way, local measurements (i.e., the drill resistance and the electric resistance measurements) are still necessary.
      PubDate: 2016-09-16T03:01:27.493721-05:
      DOI: 10.1002/stc.1935
  • Event‐driven strain cycle monitoring of railway bridges using a wireless
           sensor network with sentinel nodes
    • Authors: Nemanja Popovic; Glauco Feltrin, Khash‐Erdene Jalsan, Michal Wojtera
      Abstract: Due to the increasing traffic volume on the European railway network, the remaining fatigue life of existing steel bridges is a major concern. Several investigations demonstrated that supplementing the assessment with monitoring data enables to achieve more reliable remaining fatigue life estimations. In this paper, an event‐driven monitoring system based on a wireless sensor network that consists of two functionally different components was designed and tested. Sentinel nodes, which were mounted on the track, were used for detecting approaching trains and alerting with alarm messages the monitoring nodes. These nodes, which were mounted on the bridge, started strain sensing and data recording after receiving the alarm message and went back to a power saving mode upon completion. An embedded data processing algorithm transformed the recorded raw data into a much smaller data set representing strain cycles. A test deployment on a railway bridge demonstrated that train detection and alarming was fast and reliable. The combination of event‐driven monitoring and embedded data processing allowed to extend the battery lifetime of monitoring nodes to several months.
      PubDate: 2016-09-16T02:57:47.760465-05:
      DOI: 10.1002/stc.1934
  • Analysis of measurement and simulation errors in structural system
           identification by observability techniques
    • Authors: Jun Lei; José Antonio Lozano‐Galant, María Nogal, Dong Xu, José Turmo
      Abstract: During the process of structural system identification, errors are unavoidable. This paper analyzes the effects of measurement and simulation errors in structural system identification based on observability techniques. To illustrate the symbolic approach of this method a simply supported beam is analyzed step‐by‐step. This analysis provides, for the very first time in the literature, the parametric equations of the estimated parameters. The effects of several factors, such as errors in a particular measurement or in the whole measurement set, load location, measurement location or sign of the errors, on the accuracy of the identification results are also investigated. It is found that error in a particular measurement increases the errors of individual estimations, and this effect can be significantly mitigated by introducing random errors in the whole measurement set. The propagation of simulation errors when using observability techniques is illustrated by two structures with different measurement sets and loading cases. A fluctuation of the observed parameters around the real values is proved to be a characteristic of this method. Also, it is suggested that a sufficient combination of different load cases should be utilized to avoid the inaccurate estimation at the location of low curvature zones. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-09-05T22:20:37.845282-05:
      DOI: 10.1002/stc.1923
  • Structural model updating using incomplete transfer function and modal
    • Authors: Maria Farshadi; Akbar Esfandiari, Maryam Vahedi
      Abstract: Structural damage detection by non‐destructive techniques has been investigated widely by researchers in recent years, and several response‐based Structural Health monitoring techniques have been developed. In this paper, a vibration‐based damage detection algorithm through model updating utilizing incomplete frequency response function and modal data is presented. First, a modified sensitivity equation is presented to relate the changes of mode shapes to the changes of unknown structural parameters. Then, the developed equations are used to correlate changes of frequency response functions to the changes of structural parameters. Parameter estimation is conducted through least square solution of sensitivity equations. In order to prove the capability of the proposed method for structural damage detection purpose, a numerical example using error contaminated data is presented. Results exhibit robustness of method against measurement and mass modeling errors.
      PubDate: 2016-09-01T02:55:32.093935-05:
      DOI: 10.1002/stc.1932
  • Impact event identification in thin plates through real strain
    • Authors: Mijia Yang; Saeed Ahmari, Majura Selekwa
      Abstract: Impact event identification is a primary concern in many structural health monitoring applications. Model‐based inverse analysis is a common approach for system identification as long as the physical model can accurately capture the behavior of structure. A layered analysis including estimation of impact location in the first layer and refinement and reconstruction of impact load time history through inverse analysis in the second layer was proposed and verified well with the numerical results previously. Due to unavoidable noises, implementation of the theory with a modified inverse scheme on a simply supported plate structure is conducted in this study. The real signal data is first prefiltered using a low pass filter. Different alternatives are then proposed for the inverse scheme, and a new parameter, normalized signal energy, is adopted for layer 1 due to its convenience and accuracy compared with the traditional one, that is, the time of flight method. Signal power and filtered signal data are used for layer 2 of the inverse procedure. The results indicate that the modified inverse scheme is capable of detecting impact location and reconstructing impact load time history with a satisfactory precision.
      PubDate: 2016-08-30T03:41:19.927668-05:
      DOI: 10.1002/stc.1933
  • A method of pipeline corrosion detection based on hoop‐strain
           monitoring technology
    • Authors: Liang Ren; Tao Jiang, Dong‐sheng Li, Peng Zhang, Hong‐nan Li, Gang‐bing Song
      Abstract: A pipeline is often an important structure with very long service life. It is of great significance to monitor the corrosion level of a pipeline to ensure its safety operation. This paper aims to develop a new nondestructive method to detect the pipeline corrosion. It is assumed that the pipeline corrosion will result in a variation of the circumferential strain. The nondestructive detection method is based on a novel fiber Bragg grating (FBG) hoop‐strain sensor, which can accurately measure the circumferential strain of a pipeline. In this paper, the theoretical study and numerical analysis based on finite element method are detailed in our initial work. Then, tests are conducted on three steel pipes to verify the effectiveness and accuracy of this method. The results demonstrate that the FBG hoop‐strain sensor has good performance in the circumferential strain measurement and is sensitive to the variation of the circumferential strain caused by different corrosion level. The FBG hoop‐strain sensor is considered to be a promising device in pipeline corrosion monitoring. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-30T03:30:33.837977-05:
      DOI: 10.1002/stc.1931
  • Optimal sensor placement methodology for uncertainty reduction in the
           assessment of structural condition
    • Authors: Wei Yang; Limin Sun, Gang Yu
      Abstract: This paper introduces a novel approach for selecting sensor positions for uncertainty reduction in the assessment of structural condition, where the main difficulty is how to quantify the uncertainty. In order to tackle this problem, a condition index, which is a linear combination of the finite‐element model parameters, is defined. By taking the multiplying coefficient equal to the vulnerability index corresponding to each model parameter, the linearized condition index is able to reflect the influence of local damage on the global damage condition. The uncertainty in the estimate of this linearized condition index can be readily quantified from the uncertainty in the updated model parameters. Bayesian finite‐element model updating is applied for uncertainty quantification in the model parameters. The procedure of the proposed method is illustrated by designing the optimal sensor configuration for a truss structure model. The simulated damage and condition assessment of the truss structure shows that the proposed method is effective in reducing the uncertainty in the condition assessment. Furthermore, it is demonstrated that the proposed method is useful for a more important reason: it can reduce the uncertainty in the damage assessment of vulnerable substructure. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-30T03:28:01.759033-05:
      DOI: 10.1002/stc.1927
  • 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
    • Authors: James Long; Oral Büyüköztürk
      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
    • Authors: H. Jeon; S. Choi, J.‐U. Shin, Y. Kim, H. Myung
      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
    • Authors: C. Tutivén; Y. Vidal, J. Rodellar, L. Acho
      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
    • 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
    • Authors: Gang Yan; Hao Sun, Oral Büyüköztürk
      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
    • 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
    • Authors: Lun‐hai Zhi; Ming‐xin Fang, Q.S. Li
      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
    • Authors: Jia‐zhan Su; Yong Xia, Yi‐qing Ni, Lin‐ren Zhou, Cheng Su
      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
    • 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
    • Authors: Shih‐Yu Chu; Shih‐Wei Yeh, Lyan‐Ywan Lu, Chih‐Hua Peng
      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
  • Issue Information
    • Pages: 1385 - 1387
      Abstract: No abstract is available for this article.
      PubDate: 2016-11-03T23:57:29.955851-05:
      DOI: 10.1002/stc.1797
  • Integrating sensing elements on external fixators for healing assessment
           of fractured femur
    • Authors: W. H. Ong; W. K. Chiu, M. Russ, Z. K. Chiu
      Pages: 1388 - 1404
      Abstract: This paper highlights the potential of integrating SHM concepts into an external fixator with the aim of using it to assess the healing of a fractured femur. A finite element analysis was first performed on the fixated femur to understand the response of the fixated femur in its fractured and healed state. The underlying mechanics will be used to establish a suitable monitoring strategy for assessment of healing. The results will be supported by a series of experiments using a fixated saw-bone femur, which has been cut to simulate fracture. The cut was filled with epoxy, and the curing of this epoxy was used to simulate healing of the fractured region. The findings lead to an actuation and sensing protocol able to determine the state of union of a fixated long bone. This methodology was tested further by using modelling clay to approximate the mass added by soft tissue surrounding the bone. These results illustrate that the integration of SHM and orthopaedic concepts can provide a quantitative measure that can be used in conjunction with existing techniques for the monitoring of the state of healing of the fracture. This represents a significant potential of reducing or eliminating the qualitative healing assessment. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-11T03:57:15.892639-05:
      DOI: 10.1002/stc.1843
  • Target-free approach for vision-based structural system identification
           using consumer-grade cameras
    • Authors: Hyungchul Yoon; Hazem Elanwar, Hajin Choi, Mani Golparvar-Fard, Billie F. Spencer
      Pages: 1405 - 1416
      Abstract: Recent reports on America's infrastructure have emphasized the importance of structural health monitoring of civil infrastructures. System identification is a key component of many structural health monitoring strategies. Current system identification methods estimate models of a structure by measuring displacements, accelerations, and strains with wired or wireless sensors. However, these methods typically involve installation of a limited number of sensors at discrete locations and require additional data acquisition devices. To overcome these limitations, computer vision-based techniques have been introduced recently that employ high-speed and high-resolution cameras. Such cameras can be quite costly and require tedious installation of targets. This paper investigates the potential of using consumer-grade cameras for structural system identification without the need to install targets. The underlying methods for target-free displacement measurements are introduced, including region of interest selection, feature detection, point tracking, and outlier removal. A set of experiments are conducted to assess the efficacy of the proposed approach by comparing the accuracy of the identified model with one obtained using a conventional wired system. Careful comparison of the results demonstrates the significant potential of the proposed approach. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-11T04:00:20.046955-05:
      DOI: 10.1002/stc.1850
  • Aeroelastic control of long-span suspension bridges with controllable
    • Authors: Konstantinos Nikolaos Bakis; Matteo Massaro, Martin S. Williams, David J. N. Limebeer
      Pages: 1417 - 1441
      Abstract: The structural-aerodynamic modelling and dynamic stabilization of a three-dimensional suspension bridge model is considered. Our emphasis is on investigating the effectiveness of leading and trailing edge flaps in suppressing aeroelastic instabilities. The East Great Belt Bridge is chosen as a design example, and its aeroelastic limits are computed using both thin aerofoil theory and flutter derivatives. The problem is cast in an efficient reduced size finite element formulation with aerodynamic forces expressed in the Laplace domain by use of a high-fidelity rational function approximation. Circulatory aerodynamic forces are modelled using a feedback loop for every element, and the problem is expressed in a form suitable for implementation of modern control techniques. The structure's full multimodal response is considered, and numerical predictions show very good agreement against experimental data from the literature. In order to account for modelling errors and uncertainties while designing the controller, elements from robust control theory are invoked. The stability and robustness of the bridge when fitted with flaps controlled by optimal and suboptimal H∞ controllers are discussed for varying lengths of control surfaces along the suspended span as the optimum configuration for aerodynamic performance is investigated. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-15T02:02:29.874453-05:
      DOI: 10.1002/stc.1839
  • Detection of fatigue damage precursor using a nonlinear vibration approach
    • Authors: Ed Habtour; Daniel P. Cole, Jaret C. Riddick, Volker Weiss, Mark Robeson, Raman Sridharan, Abhijit Dasgupta
      Pages: 1442 - 1463
      Abstract: A nonlinear dynamic methodology is developed for detecting and estimating fatigue damage precursor in isotropic metal structures, prior to fatigue crack initiation, based on measurement of changes in the structure nonlinear response to harmonic base excitation. As an example, a damage precursor feature was extracted for cantilever beams by quantifying the reduction in the nonlinear stiffness because of localized microscopic material softening. The nonlinear dynamic analytical model parametrically tracks changes in the nonlinear structural stiffening as a function of the structural response and the loading cycles. Experimental results are obtained by exciting the base of cantilever beams at various amplitude levels. At high response amplitudes, the beams experience three competing simultaneous nonlinear dynamic mechanisms: (i) stiffening because of high response amplitude at the fundamental mode; (ii) softening because of inertial forces; and (iii) softening because of localized microscopic material damage caused by cyclic micro-plasticity. The third mechanism—a potential precursor to fatigue crack initiation in the structure—resulted in a cumulative softening because of early accumulation of cyclic fatigue damage and is the focus of this study. The loading intensity and the number of cycles influenced the relative contribution of these dynamic mechanisms. Nanoindentation studies near the beam clamped boundary were conducted to confirm the fatigue degradation in the local mechanical properties as a function of loading cycles. The proposed detection method is simple to implement and detects the presence of damage precursors but lacks the resolution to discern spatial distributions of the damage intensity. Based on prior knowledge of the structural dynamic characteristics of the beam and using the proposed methodology, damage level and stiffness reduction can be detected and estimated based on changes in the nonlinear structural response. The nonlinear stiffness term in the equation of motion is found to be very sensitive to the proposed fatigue damage precursor, making it an effective method for monitoring structural degradation prior to crack developments. The proposed methodology provides new insights and constitutes a significant step toward the development of new inspection techniques. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-16T04:56:01.343704-05:
      DOI: 10.1002/stc.1844
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