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  Subjects -> ENERGY (Total: 307 journals)
    - ELECTRICAL ENERGY (2 journals)
    - ENERGY (183 journals)
    - ENERGY: GENERAL (8 journals)
    - NUCLEAR ENERGY (30 journals)
    - PETROLEUM AND GAS (53 journals)
    - RENEWABLE ENERGY (31 journals)

ENERGY (183 journals)                 | Last

Showing 1 - 200 of 406 Journals sorted alphabetically
ActaEnergetica     Open Access  
Advances in Building Energy Research     Hybrid Journal   (Followers: 9)
Advances in Energy and Power     Open Access   (Followers: 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: 8)
Annual Reports on NMR Spectroscopy     Full-text available via subscription   (Followers: 3)
Annual Review of Resource Economics     Full-text available via subscription   (Followers: 12)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Solar Energy     Hybrid Journal   (Followers: 16)
Archives of Thermodynamics     Open Access   (Followers: 8)
Artificial Photosynthesis     Open Access   (Followers: 1)
Asian Bulletin of Energy Economics and Technology     Open Access   (Followers: 2)
Atomic Energy     Hybrid Journal   (Followers: 4)
Atoms for Peace: an International Journal     Hybrid Journal   (Followers: 3)
Batteries     Open Access   (Followers: 3)
Biofuel Research Journal     Open Access   (Followers: 4)
Biofuels     Hybrid Journal   (Followers: 10)
Biofuels Engineering     Open Access  
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Bulletin de droit nucleaire     Full-text available via subscription   (Followers: 1)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 40)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 21)
Carbon Management     Hybrid Journal   (Followers: 6)
Catalysis for Sustainable Energy     Open Access   (Followers: 6)
CERN courier. International journal of high energy physics     Free   (Followers: 7)
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: 4)
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: 21)
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 & Environment     Hybrid Journal   (Followers: 17)
Energy & Fuels     Full-text available via subscription   (Followers: 26)
Energy and Buildings     Hybrid Journal   (Followers: 10)
Energy and Emission Control Technologies     Open Access   (Followers: 4)
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: 10)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Harvesting and Systems : Materials, Mechanisms, Circuits and Storage     Hybrid Journal   (Followers: 3)
Energy Law Journal     Full-text available via subscription   (Followers: 4)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 17)
Energy Policy     Partially Free   (Followers: 58)
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   (Followers: 1)
Energy Strategy Reviews     Partially Free   (Followers: 9)
Energy Studies Review     Open Access   (Followers: 5)
Energy Systems     Hybrid Journal   (Followers: 13)
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: 8)
EPJ Photovoltaics     Open Access   (Followers: 4)
Facta Universitatis, Series : Electronics and Energetics     Open Access  
Foundations and Trends® in Renewable Energy     Full-text available via subscription   (Followers: 2)
Frontiers in Energy     Hybrid Journal   (Followers: 3)
Frontiers in Energy Research     Open Access   (Followers: 3)
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   (Followers: 1)
Geothermal Energy     Open Access   (Followers: 3)
Geothermal Energy Science     Open Access   (Followers: 1)
Green     Hybrid Journal   (Followers: 1)
Green Energy & Environment     Open Access   (Followers: 2)
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: 9)
IEEE Transactions on Power Systems     Hybrid Journal   (Followers: 27)
IET Power Electronics     Hybrid Journal   (Followers: 26)
Ingeniería Energética     Open Access  
Innovations : Technology, Governance, Globalization     Hybrid Journal   (Followers: 12)
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: 9)
International Journal of Emerging Electric Power Systems     Hybrid Journal   (Followers: 5)
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: 2)
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 Global Energy Issues     Hybrid Journal   (Followers: 8)
International Journal of Green Energy     Hybrid Journal   (Followers: 9)
International Journal of Hydrogen Energy     Partially Free   (Followers: 14)
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: 4)
International Journal of Nuclear Governance, Economy and Ecology     Hybrid Journal   (Followers: 2)
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 Ocean and Climate Systems     Open Access   (Followers: 7)
International Journal of Power and Energy Conversion     Hybrid Journal   (Followers: 3)
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: 9)
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 Computational Multiphase Flows     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: 2)
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: 8)
Journal of Nano Energy and Power Research     Full-text available via subscription   (Followers: 4)
Journal of Nuclear Energy Science & Power Generation Technology     Hybrid Journal   (Followers: 2)
Journal of Ocean Engineering and Marine Energy     Hybrid Journal   (Followers: 2)
Journal of Physical Chemistry C     Full-text available via subscription   (Followers: 28)
Journal of Power Electronics & Power Systems     Full-text available via subscription   (Followers: 8)
Journal of Radiological Protection     Full-text available via subscription   (Followers: 4)
Journal of Renewable Energy     Open Access   (Followers: 6)
Journal of Semiconductors     Full-text available via subscription   (Followers: 3)
Journal of Solar Energy     Open Access   (Followers: 8)
Journal of Solar Energy Engineering     Full-text available via subscription   (Followers: 18)
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: 8)
Natural Resources     Open Access   (Followers: 2)
Nature Energy     Hybrid Journal   (Followers: 5)
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: 12)
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   (Followers: 1)
Radiochimica Acta     Hybrid Journal   (Followers: 5)
Radioprotection     Hybrid Journal   (Followers: 1)
Science and Technology of Nuclear Installations     Open Access   (Followers: 2)
Smart Grid and Renewable Energy     Open Access   (Followers: 9)
Solar Energy     Hybrid Journal   (Followers: 20)
Solar Energy Materials and Solar Cells     Hybrid Journal   (Followers: 32)
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: 7)
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  
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: 14)
Wiley Interdisciplinary Reviews : Energy and Environment     Hybrid Journal   (Followers: 5)
Wind Energy     Hybrid Journal   (Followers: 4)
Wind Engineering     Hybrid Journal   (Followers: 3)

       | Last

Journal Cover Structural Control and Health Monitoring
  [SJR: 1.549]   [H-I: 35]   [7 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  [1616 journals]
  • Pixel-wise structural motion tracking from rectified repurposed videos
    • Authors: Ali Khaloo; David Lattanzi
      Abstract: After any disaster, there is an immediate need to assess the integrity of local structures. When available, the displacement time history of a structure during the event can provide an invaluable source of triage assessment information. Although conventional sensors such as accelerometers readily provide this information, many structures are not instrumented and in these cases an alternative is needed. This paper presents such an alternative: a flexible, low-cost, and target-free approach to extracting motion time histories from video recordings of structures during an event. The approach is designed for scenarios where video recordings have inadvertently captured a dynamic event, with the goal of repurposing them for structural triage assessment through a combination of computer vision and signal processing techniques. A combination of parametric video stabilization, 3D denoising, and outlier robust camera motion estimation are employed to mitigate of the effects of camera motion and video encoding artifacts. The approach leverages the computer vision concept of optical flow to provide motion estimates, and 4 canonical optical flow algorithms are assessed as part of this study. The developed approach was validated on the records of the Network for Earthquake Simulation database. The overall findings indicate that the developed method is effective at reconstructing dynamic structural time histories, though the choice of optical flow algorithm plays a significant role in the overall performance. In particular, any employed optical flow algorithm must not overpenalize the high motion gradients that occur at the boundary of in-motion buildings and the image background.
      PubDate: 2017-03-17T04:15:55.65563-05:0
      DOI: 10.1002/stc.2009
       
  • A control framework for uniaxial shaking tables considering tracking
           performance and system robustness
    • Authors: Pei-Ching Chen; Chin-Ta Lai, Keh-Chyuan Tsai
      Abstract: Shaking table testing has been regarded as one of the most straightforward experimental approaches to evaluate the seismic response of structures subjected to earthquake ground motions. Therefore, reproducing an acceleration time history accurately becomes crucial for shaking table testing. In this study, a control framework for uniaxial shaking tables is proposed which incorporates a feedback controller into a weighted command shaping controller. It implements through outer-loop control in addition to the conventional existing proportional-integral inner-loop control. The model-based command shaping controller which considers the control-structure interaction can be designed to shape either displacement or acceleration references. The weightings for the shaped displacement and acceleration can be calculated by a linear interpolation algorithm which considers the dominant frequency of the desired acceleration time history as well as the correlation between the displacement and acceleration responses of the shaking table. Accordingly, the weighted combination of the shaped displacement and acceleration generates the control command to the shaking table. On the other hand, the feedback controller deals with the system uncertainty and modeling error. Loop-shaping design method is adopted to synthesize the feedback controller. Finally, the control framework is verified by several shaking table tests with and without a flexible specimen. Experimental results demonstrate the performance and robustness of the proposed control framework for shaking table test systems.
      PubDate: 2017-03-17T04:15:40.846885-05:
      DOI: 10.1002/stc.2015
       
  • Guided waves for damage identification in pipeline structures: A review
    • Authors: Ruiqi Guan; Ye Lu, Wenhui Duan, Xiaoming Wang
      Abstract: Guided waves find their niche in cost-effective damage identification in comparison with conventional nondestructive evaluation. Comprehensive research has been conducted since the 1980s, focusing on the detection of a wide variety of types of damage in metallic and composite structures. The main scope of this paper is to present a review of state-of-the-art guided wave-based approaches for damage identification in pipeline structures. Theoretical analyses of the interaction between linear and nonlinear guided waves and damage are addressed in detail. Numerical simulations and experimental studies of damage identification in pipeline structures using both linear and nonlinear guided waves are elaborated. Other issues including bends in pipes, effects of environmental and operational conditions on the performance of guided waves are another focus of this review. Future challenge in this field is summarised at the end of this review.
      PubDate: 2017-03-17T03:45:54.770713-05:
      DOI: 10.1002/stc.2007
       
  • Source location using an optimized microfiber coupler sensor based on
           modal acoustic emission method
    • Authors: Linjie Wang; Yiying Liu, Wencheng Fu, Fengmei Li, Zhenyu Zhao, Ke Yu
      Abstract: This paper demonstrates the application of an optimized microfiber coupler sensor (MFCS) to the source location with modal acoustic emission (MAE) method. First, based on analyzing the key influence factors of MAE method application, the package optimization of MFCS has been investigated. It is found that the best packaging length is from the groove end to the place where the 2 fibers just begin to fuse, which could achieve both, good completeness of acoustic emission signal wavelet transform and relative high sensitivity. Then, the linear source localization has been performed using the optimized MFCS. The arrival time of the acoustic emission signal is decided by the contour threshold of the wavelet transform to avoid the wave reflection from edge and mode conversion. The locating accuracy with different thresholds is analyzed. It indicates that the result agrees with the actual source position better when higher threshold is set. Furthermore, considering noise contamination and the frequency components completeness, the appropriate range of threshold is suggested to the location calculation. Finally, the favorable localization result proves that applying this optimized MFCS to the MAE source location strategy is quite feasible.
      PubDate: 2017-03-15T22:56:24.290647-05:
      DOI: 10.1002/stc.2011
       
  • Fuzzy pattern recognition technique for crack propagation on earplate
           connection of guyed mast under wind load
    • Authors: Xueliang Wang; Weilian Qu, Hui Liu, Juan M. Caicedo, Xiaoli Wang, Xinxue Wang
      Abstract: A 2-stage damage identification technique is presented for identifying crack lengths on cable-tower connections of guyed masts. It is based on fuzzy pattern recognition theory and uses the cable force and the strain at the key locations of the earplate connection as input parameters. The methodology is developed with a numerical model under stochastic wind excitation and verified by numerical simulation and experiment. First, the relationships of cable force, strain on the connection, and crack length are explored. The wind-induced responses of guyed mast are analyzed under different wind speed and directions to form a database of cable forces. The responses of a typical connection with different crack lengths are simulated to investigate the strain sensitivity to crack propagation. Its results are used to form a second-stage strain database. The first stage of the fuzzy identification consists in identifying the interval of cable forces on the basis of cable force measurements. Then, a subjection degree function is formed between the measured strain and the developed strain database to judge the damage state of the connection by identifying the existence of a crack and estimating its length. The results of a numerical case study and further experiment are presented and show the potential and practicability of the technique to estimate the right range of crack length on earplates. Therefore, the proposed technique is practical and feasible to predict the damage state of earplate and can provide valuable prewarning information for structural safety.
      PubDate: 2017-03-13T02:20:44.103097-05:
      DOI: 10.1002/stc.2010
       
  • Multi-objective optimal design of tuned mass dampers
    • Authors: Oren Lavan
      Abstract: This paper first presents a multi-objective optimization problem formulation for the design of a tuned mass damper (TMD) for either a base excitation or an external load. The optimization seeks to simultaneously minimize structural responses, the TMD mass and the TMD stroke. A white noise input is adopted to represent the base acceleration or the external load. Alternatively, a filtered white noise could be used. Furthermore, the TMD is assumed to be tuned to dampen one of the modes of the structure, typically the first mode. Two approaches for the solution of the problem are then presented. The first approach directly solves the problem while considering the full multi-degree-of-freedom system and the TMD equations. Using the second approach, the multimodal response of the structure is first approximately decomposed to its modal contributions. The modal contribution of the damped mode could thus be analyzed as a single-degree-of-freedom system with a TMD. An intensive parametric study, where the response of a single-degree-of-freedom system equipped with a TMD is optimized in a multi-objective sense, is then performed. This parametric study enables gaining insight to the behavior of the problem. Furthermore, its results assist in executing the second optimization approach without having to actually run the optimization algorithm. The second approach is also implemented in an Excel spreadsheet that is attached as “Supporting Information.”
      PubDate: 2017-03-10T10:31:02.086771-05:
      DOI: 10.1002/stc.2008
       
  • Structural damage identification by extended Kalman filter with l1-norm
           regularization scheme
    • Authors: Chun Zhang; Jie-Zhong Huang, Gu-Quan Song, Lin Chen
      Abstract: The extended Kalman filter (EKF) is a powerful tool used to assess structural damage in the time domain. A method combining EKF and l2-norm regularization, such as Tikhonov regularization, is found to improve the solution of ill-posed inverse problems. However, the l2-norm regularization process may lead to an over-smooth damage identification solution, which is contradictory to the sparse and concentrated distribution of local damages. This paper presents a new damage identification algorithm based on EKF with l1-norm regularization via free vibration responses. The l1-norm regularization item is used to enhance the identification accuracy of local damages while restraining the interference of measurement noise. Afterward, the constrained minimization problem is solved by EKF endowed with a pseudomeasurement equation. The numerical and experimental examples confirm that the proposed algorithm shows good robustness and excellent accuracy of damage identification with the unknown initial structural state.
      PubDate: 2017-03-07T02:45:42.681378-05:
      DOI: 10.1002/stc.1999
       
  • Automated modal tracking in a football stadium suspension roof for
           detection of structural changes
    • Authors: Sandro Diord; Filipe Magalhães, Álvaro Cunha, Elsa Caetano, Nuno Martins
      Abstract: Considerable efforts have been made towards the development of robust and fully automated vibration-based monitoring systems with the goal of extracting relevant information regarding the dynamic behaviour and health condition of the monitored structure. Satisfactory results have been obtained in this scientific domain by combining accurate measurement systems and fully automated output-only modal identification techniques.In this context, the main objective of this contribution is to demonstrate in a full-scale case study that with the application of sophisticated algorithms for the automatic tracking of modal parameters, it is possible to detect very small structural changes. Apart from describing the main features and capabilities of the autonomous monitoring system implemented to assess the structural condition of a peculiar football stadium suspension roof, this paper also outlines the main results obtained over the course of 4 years of monitoring carried out to assess the dynamic behaviour and the health condition of the roof structure. The routines developed for the online processing of the continuously collected acceleration time series include state-of-the-art processing techniques, such as automated modal identification based on cluster analysis and principal components analyses combined with control charts for removal of environmental or operational effects and detection of structural changes, together with some innovative features in the context of continuous dynamic monitoring, such as the quantification of the uncertainties associated with each modal estimate and the estimation of the contribution of each mode to the measured structural response.
      PubDate: 2017-03-07T02:40:48.428272-05:
      DOI: 10.1002/stc.2006
       
  • Issue Information
    • Abstract: No abstract is available for this article.
      PubDate: 2017-03-03T00:48:06.980903-05:
      DOI: 10.1002/stc.1941
       
  • Color and depth data fusion using an RGB-D sensor for inexpensive and
           contactless dynamic displacement-field measurement
    • Authors: Yulu Luke Chen; Mohamed Abdelbarr, Mohammad R. Jahanshahi, Sami F. Masri
      Abstract: There are numerous applications in the field of structural dynamics that require the accurate measurement of evolving deformation fields. Although there are several sensors for direct displacement measurements at a specific point in a uniaxial direction or multicomponent deformations, there are only very limited, and relatively quite expensive, methodologies for obtaining the 3-dimensional components of a displacement of a dynamically evolving (i.e., not pseudostatically) deformation field. This paper reports the results of a comprehensive experimental study to assess the accuracy and performance of a class of inexpensive vision-based sensors (i.e., RGB-D sensors) to acquire dynamic measurements of the displacement field of a test structure. The sensor was subjected to a broad variety of different dynamic motions of varying amplitude and spectral characteristics and with varying configurations of the position and orientation of the sensor with respect to the target structure. Particular attention was devoted to quantifying the influence of various test conditions, such as amplitude, frequency, sampling rate, spatial distortion, and relationships between the RGB pixel-based measurements and the depth measurements. It is shown that the class of sensors under discussion, when operated under the performance envelope discussed in this paper, can provide, with acceptable accuracy, a very convenient and simple means of quantifying 3-dimensional displacement fields that are dynamically changing at relatively low-frequency rates typically encountered in the structural dynamics field.
      PubDate: 2017-03-02T22:25:41.375428-05:
      DOI: 10.1002/stc.2000
       
  • Bayesian estimation of acoustic emissions source in plate structures using
           particle-based stochastic filtering
    • Authors: Debarshi Sen; Kalil Erazo, Satish Nagarajaiah
      Abstract: The application of particle-based stochastic filters to acoustic emission source localization in plate structures is presented. The approach employs time-of-flight measurements of guided waves using triangulation to estimate the acoustic emission source coordinates in a probabilistic framework using Bayesian inference, incorporating uncertainties related to material properties, measurement noise, and geometry of the system of interest. The estimate of the source location is given by a probability density function conditional on the guided wave measurements, found using particle-based stochastic simulation algorithms; in this setting, a set of particles is used to explore the space of possible source locations and efficiently estimate the posterior. The use of 2 filters is explored: the ensemble Kalman filter and the particle filter. The former filter assumes that the posterior distribution can be approximated by a Gaussian distribution, although the latter provides a nonparametric estimate of the posterior in the form of a weighted set of samples, overcoming the challenges related to the evaluation of high-dimensional integrals in an efficient way. Results of an experimental validation study conducted in a laboratory environment demonstrate the accuracy and efficiency of the particle filter-based approach. In particular, it is shown that the proposed particle filter-based approach has the capability to locate the emission source under minimal instrumentation, providing confidence intervals as a quantitative measure of the uncertainty in the estimates.
      PubDate: 2017-03-01T00:15:40.321169-05:
      DOI: 10.1002/stc.2005
       
  • Evaluation of the masonry and timber structures of San Francisco Church in
           Santiago de Cuba through nondestructive diagnostic methods
    • Authors: Riccardo D. De Ponti; Lorenzo Cantini, Laura Bolondi
      Abstract: Recently, due to a renewed interest in the religious architectural heritage of the Caribbean island of Cuba, some important interventions for the restoration and reinforcement of the colonial churches of the island were carried out. The authors, collaborating with the Archdiocese of Santiago de Cuba in a project concerning the protection of Cuban churches, applied some nondestructive and noninvasive destructive tests for an in-depth study of the main characteristics of those structures. The diagnostic method, developed mainly for the historical buildings or monuments of Europe and North America, was used to study some peculiarities of the building construction traditions of this area. The proposed techniques revealed the existence of several original solutions, for example, defenses for seismic mitigation, developed to resist the earthquakes that frequently affect the area.
      PubDate: 2017-02-21T00:16:50.849083-05:
      DOI: 10.1002/stc.2001
       
  • Implementation of a long-term monitoring approach for the operational
           safety of highway tunnel structures in a severely seismic area of China
    • Authors: Bo Wang; Zhe Zhang, Chuan He, Hao-long Zheng
      Abstract: With the rapid development of highway and railway transportation in China, many tunnels are constructed at the same time within the same region. It has become a challenge how to control dynamically such a large number of tunnel structures in long-term operation and ensure their safety. In this work, we focus on the construction of common characteristics of these tunnels built during the same period in the same region. In particular, we propose a concept and a systematic component of long-term health monitoring and develop a representative system of tunnel structure for such regional tunnels. Aiming at the engineering background, we consider the soft-rock tunnels in the Guang-Gan Expressway (GGE), which are located at the core of the Wenchuan earthquake zone, taking the Dujiashan Tunnel as a representative project. Based on the loading data of the secondary lining from long-term monitoring, the fuzzy model is employed to evaluate the structure conditions for its safety. On the basis of such theoretical analysis, we therefore establish the relationships between the representative project and other soft-rock tunnels, and then the structural safety status of the nonrepresentative project is deduced and achieved. The present study shows that the vast majority of segments of the soft-rock tunnels on the GGE are safe. At the same time, the network transmission hardware platform and security evaluation with the alerting software system are installed successfully for those tunnels. Using the long-term health monitoring and representative system of tunnel structure for soft-rock tunnels at the core of the Wenchuan earthquake zone, real-time monitoring and management of the safe status of all the soft-rock tunnels on the GGE across the entire life cycle can be realized.
      PubDate: 2017-02-16T01:25:55.616278-05:
      DOI: 10.1002/stc.1993
       
  • Damage detection under varying temperature using artificial neural
           networks
    • Authors: Jianfeng Gu; Mustafa Gul, Xiaoguang Wu
      Abstract: To avoid false alarms for vibration-based structural damage detection methods, temperature effects on damage-sensitive features should be eliminated. In this paper, a novel two-step damage identification method combining a multilayer neural network and novelty detection is developed to differentiate the changes in natural frequencies (one of the most commonly used damage features that can be obtained reliably and relatively easily) due to damage from those induced by temperature variations. In the first step, a multilayer artificial neural network, which resembles an auto-associative neural network but uses temperature variables in addition to the frequencies as the inputs, is explored to identify patterns in frequencies of undamaged structures under varying temperatures. Euclidean distance is then utilized as a novelty index to quantify the discordancy between patterns in undamaged cases and candidate cases. Numerical studies using a simply supported beam and finite element models based on an experimental grid structure, which simulate different levels of stiffness reductions under varying temperature conditions, are used to verify the detectability and robustness of the proposed approach. It is shown that the incorporation of the proposed artificial neural network with novelty detection enables one to robustly distinguish damage occurrence and severity regardless of temperature variations and noise perturbations. Using an unsupervised learning scheme, the proposed approach transforms a multivariate analysis using modal frequencies and temperature data into a straightforward univariate discordancy test using the novelty index. Given these competitive advantages, this approach is very attractive for the development of an automated continuous monitoring system in practical applications.
      PubDate: 2017-02-16T01:25:43.613289-05:
      DOI: 10.1002/stc.1998
       
  • Low-force magneto-rheological damper design for small-scale structural
           control
    • Authors: Benjamin D. Winter; R. Andrew Swartz
      Abstract: Small-scale experimental testbeds fulfill an important role in the validation of multi-degree-of-freedom systems with distributed semi-active control, by providing a necessary platform for laboratory validation of key elements of control algorithms. Development of such small-scale testbeds is hampered by difficulties in actuator construction. In order to be a useful analog to full-scale structures, actuators for small-scale test beds should exhibit similar features and limitations as their full-scale counterparts. In particular, semi-active devices, such as magneto-rheological (MR)–fluid dampers, with limited authority (compared to alternatives such as active mass dampers) and nonlinear behavior are difficult to mimic over small force scales because of issues related to fluid containment and friction. In this study, a novel extraction-type small-force MR damper, which exhibits nonlinear hysteresis similar to a full-scale MR device, is proposed, and its behavior is characterized. This actuator is a necessary development to enable the function of small-scale structural control testbeds intended for experimental structural control validation studies. Experimental validation of this prototype as a structural control device is conducted using a three-story small-scale structure subjected to simulated seismic excitation. The actuator is commanded by a wired control computer that executes a linear-quadratic-Gaussian state feedback control law augmented by a modified Bouc–Wen lookup table, both previously developed for full-scale MR applications.
      PubDate: 2017-02-16T01:16:06.362645-05:
      DOI: 10.1002/stc.1990
       
  • A particle filter-based model selection algorithm for fatigue damage
           identification on aeronautical structures
    • Authors: Francesco Cadini; Claudio Sbarufatti, Matteo Corbetta, Marco Giglio
      Abstract: The early diagnosis of cracks in aeronautical structures is a fundamental task for the safe system operation and the optimization of maintenance policies, in view of the increasing interest in life extension programs of several high-investment industries. In principle, these tasks could be fulfilled within a condition-based framework, where direct or indirect observations of the degradation evolution are processed, possibly in real time, by proper diagnostic computational tools. In the past, several attempts have been made to build real-time monitoring systems collecting strain signals acquired from sensor networks. However, in real applications, some issues remain unresolved, for example, the large number of observations available to be handled within a unique diagnostic framework, their relationship with the underlying crack size, and their typical large uncertainties. In this paper, we provide a practical solution by innovatively combining a particle filtering-based model identification algorithm with a measurement system exploiting real-time observations of the crack length reconstructed by a committee of artificial neural networks. The artificial neural networks are trained by simulated strain fields generated by a finite element model. The resulting tool allows to perform an automatic, simultaneous, and real-time (a) selection of the model more properly describing the system state evolution, so as to detect the crack propagation onset time, (b) estimation of the model parameters, and (c) estimation of the crack length, within a unique probabilistic framework based on particle filtering. The methodology is demonstrated with reference to a real helicopter panel subject to fatigue and equipped with a fiber Bragg grating sensor network.
      PubDate: 2017-02-16T01:15:56.61959-05:0
      DOI: 10.1002/stc.2002
       
  • Bayesian model updating of a full-scale finite element model with
           sensitivity-based clustering
    • Authors: Jinwoo Jang; Andrew Smyth
      Abstract: Model updating based on vibration response measurements is a technique for reducing inherent modeling errors in finite element (FE) models that arise from simplifications, idealized connections, and uncertainties with regard to material properties. Updated FE models, which have relatively fewer discrepancies with their real structural counterparts, provide more in-depth predictions of the dynamic behaviors of those structures for future analysis. In this study, we develop a full-scale FE model of a major long-span bridge and update the model to improve an agreement between the identified modal properties of the real measured data and those from the FE model using a Bayesian model updating scheme. Sensitivity-based cluster analysis is performed to determine robust and efficient updating parameters, which include physical parameters having similar effects on targeted natural frequencies. The hybrid Monte Carlo method, one of the Markov chain Monte Carlo sampling methods, is used to obtain the posterior probability distributions of the updating parameters. Finally, the uncertainties of the updated parameters and the variability of the FE model's modal properties are evaluated.
      PubDate: 2017-02-16T01:10:53.545867-05:
      DOI: 10.1002/stc.2004
       
  • New approach for monitoring historic and heritage buildings: Using
           terrestrial laser scanning and generalised Procrustes analysis
    • Authors: Hasan Abdulhussein Jaafar; Xiaolin Meng, Andrew Sowter, Paul Bryan
      Abstract: Numerous different techniques and instruments can be used for structural monitoring with different requirements producing different results. For instance, some techniques need to use embedded sensors inside the building, such as geotechnical sensors. However, this method cannot be used for historic and heritage buildings. Other methods can offer high quality, but with a low point density and require fixed stations and targets, such as total stations. In such a case, the location of deformation tends to be known, such as dams, bridges, high-rise buildings, and so forth. Nevertheless, this is not the case for historic and heritage buildings where each block could be subject to deformation. The challenge in such a case is to detect the deformation without any previous knowledge. The aim of this research is to develop a new approach to detect and localise unpredictable deformation. It is based on terrestrial laser scanner measurements and generalised Procrustes analysis techniques to determine deformation vectors, although boxing structure and F-tests are used to detect and localise deformation. In summary, after applying this approach, the whole concerned building is represented as parts, for each of them, the displacement vector and deformation probability are estimated. Validation experiments have shown the capability of the proposed method to detect and localise deformation with magnitude less than noise level in simulated data and of subcentimetre level for ranges up to 10 m in real scan data. Finally, the new approach has been applied to an English Historic site, Bellmanpark Limeklins.
      PubDate: 2017-02-09T23:11:46.093351-05:
      DOI: 10.1002/stc.1987
       
  • Seismic FDD modal identification and monitoring of building properties
           from real strong-motion structural response signals
    • Authors: Fabio Pioldi; Rosalba Ferrari, Egidio Rizzi
      Abstract: In the present study, output-only modal dynamic identification and monitoring of building properties is attempted successfully by processing real earthquake-induced structural response signals. This is achieved through an enhanced version of a recently-developed refined Frequency Domain Decomposition (rFDD) approach, which in the earlier implementation was adopted to analyse synthetic seismic response signals only. Despite that short duration, nonstationary seismic response data and heavy structural damping shall not fulfil traditional Operational Modal Analysis assumptions, the present rFDD response-only algorithm allows for the effective estimation of strong-motion natural frequencies, mode shapes, and modal damping ratios, with real seismic response signals. The present rFDD enhancement derives from a preprocessing time-frequency analysis and from an integrated approach for Power Spectral Density matrix computation, which constitute crucial innovative issues for the treatment of real earthquake response data. A monitoring case study is analysed by taking the real strong-motion response records from a seven-storey reinforced concrete building in Van Nuys, California, from 1987 to the latest 2014 events (Center of Engineering Strong Motion Data database), as recorded before, during and after the 1994 Northridge earthquake, which severely damaged the building (then retrofitted). This paper proves the effectiveness of the proposed enhanced rFDD algorithm as a robust method for monitoring current structural modal properties under real earthquake excitations. This shall allow for identifying possible variations of structural features along experienced seismic histories, providing then a fundamental tool towards Earthquake Engineering and Structural Health Monitoring purposes.
      PubDate: 2017-02-09T22:50:53.539356-05:
      DOI: 10.1002/stc.1982
       
  • Improved semi-active control algorithm for hydraulic damper-based braced
           buildings
    • Authors: Mohsen Azimi; Akbar Rasoulnia, Zhibin Lin, Hong Pan
      Abstract: Much research has been conducted on structural control systems to improve the seismic performance of structures under earthquakes and, ultimately, offer high performance-resilient buildings beyond life risk mitigation. Among various structural control algorithms, semi-active control strategies have been widely accepted for overcoming some limitations existed in either passive or active control systems, thereby leading to better structural performance over their counterparts. In this study, a new semi-active control algorithm with minimum control parameters is developed to drive the hydraulic damper for effective control of the dynamic deformation of low- and high-rise building structures under earthquake loadings. The new controller allows less input and computation for determining the damping coefficient of the hydraulic dampers while maintaining a higher performance. V-braced buildings with three varying heights are used as prototypes to demonstrate the effectiveness of the proposed semi-active damper. Two critical parameters, maximum drift and acceleration of stories, are defined for the performance criteria. The simulation results show that the developed semi-active damper can significantly improve the seismic performance of the buildings in terms of controlled story drift and acceleration. By use of less input and reduced time delay effects, the proposed control system is comparable with those of existing semi-active controllers. The findings in this study will help engineers to design control systems for seismic risk mitigation and effectively facilitate the performance-based seismic design.
      PubDate: 2017-02-08T03:02:08.230309-05:
      DOI: 10.1002/stc.1991
       
  • Numerical simulation of acoustic emission during crack growth in 3-point
           bending test
    • Authors: A. Berezovski; M. Berezovski
      Abstract: Numerical simulation of acoustic emission by crack propagation in 3-point bending tests is performed to investigate how the interaction of elastic waves generates a detectable signal. It is shown that the use of a kinetic relation for the crack tip velocity combined with a simple crack growth criterion provides the formation of waveforms similar to those observed in experiments.
      PubDate: 2017-02-07T01:50:44.453997-05:
      DOI: 10.1002/stc.1996
       
  • Spectral characteristics of asynchronous data in operational modal
           analysis
    • Authors: Yi-Chen Zhu; Siu-Kui Au
      Abstract: Operational modal analysis (OMA) has gained popularity for identifying the modal properties of a structure for its high economy and feasibility. Conventionally, time synchronisation among data channels is required to determine mode shape. OMA can be conducted more flexibly if synchronisation is not required. The power spectral density (PSD) matrix of data and its spectral properties are often used for analysing potential modes. Conventionally known properties assume synchronous data and do not carry over to asynchronous data. This paper investigates the spectral properties of asynchronous OMA data. A stationary process with imperfect coherence is proposed that is conducive to OMA while capturing the key asynchronous characteristics. The theoretical properties of PSD matrix are derived and validated using synthetic and experimental data. Although conventional methods do not allow mode shape to be determined from asynchronous data, the present work reveals the possibility by noting that the data are measured under the same excitation and hence share a common PSD in the modal force. On this basis, a simple method is proposed for determining the mode shape. For perfectly incoherent data channels, it is not possible to determine the relative sense of their mode shape values, which is a fundamental limitation of such data. In implementation, the sense can be determined from intuition or estimated from the residual coherence between channels. Experimental application reveals practical issues in OMA with asynchronous data. This work aspires to provide the pathway for more flexible implementation of OMA, for example, using asynchronous data from multiple smart phones.
      PubDate: 2017-02-06T02:32:14.291209-05:
      DOI: 10.1002/stc.1981
       
  • Development and implementation of horizontal-plane settlement indication
           system for freeway health monitoring during underpass construction
    • Authors: Chih-Chung Chung; Chih-Ping Lin, Chi-Hsien Chin, Kun-Hsien Chou
      Abstract: This study introduced two major contributions for freeway health monitoring during the pipe roof construction and subsequent excavation to enlarge an existing underpass. First, a horizontal-plane settlement indication system (HSIS) was developed to monitor inevitable settlement due to shallow overburden above the steel pipes. Second, the experience gained from the field monitoring program was detailed with emphasis on encountered problems and countermeasures for freeway safety decision-making. On the basis of two microelectromechanical systems tilt sensors embedded as a differential pair, HSIS effectively minimizes the effect of ambient temperature whose fluctuation was expected at shallow depth. The measurement accuracy (≤4 mm) and repeatability (≤0.05 mm) were verified experimentally. Thereby, three HSIS arrays were positioned in the freeway pavement to continuously detect local settlement and based on which to issue possible alarm. The RS485 data acquisition protocol, which is characterized by fast synchronized communication, was applied for HSIS to reduce the dynamic error due to heavy traffics. The observed settlement was close to the alarm threshold, which is considered as the combination effects of the simulated settlement and the penetrating deviation during the pipe roof construction. Furthermore, an approach to account for false vertical drift due to instability of the fixed point of HSIS was proposed such that the settlement behavior during excavation phase could be effectively described. The unique implementation is a benefit to further HSIS application in practice.
      PubDate: 2017-02-06T02:31:54.767161-05:
      DOI: 10.1002/stc.1995
       
  • Low-cost simulation using model order reduction in structural health
           monitoring: Application of balanced proper orthogonal decomposition
    • Authors: N. Sepehry; M. Shamshirsaz, F. Bakhtiari Nejad
      Abstract: In this paper, both two powerful methods in structural health monitoring, Lamb wave propagation and electromechanical impedance method, are modeled, implemented, and tested to inspect the plate-like structure using piezoelectric wafer active sensor (PWAS). In order to detect damage in structure, introducing a model for advanced signal processing algorithm is essential. A three-dimensional spectral finite element method has been applied to model Lamb wave propagation and electromechanical impedance in plate with attached PWAS. In reality, Lamb wave generation and electromechanical impedance in high frequencies lead to a high degree of freedom in modeling and consequently to a low speed simulation in frequency and time domains calculation. For us to overcome this problem, balanced proper orthogonal decomposition (BPOD) has been developed and used as model order reduction for these methods in structural health monitoring. The experimental tests are carried out on aluminum plate with two attached PWAS. The simulation results obtained by BPOD and full-order method are validated by comparison with experimental ones. The results show that the proposed and implemented model order reduction method (BPOD) leads to increase significantly simulation speed without any distortion in accuracy. For Lamb wave method, CPU time consuming using BPOD is reduced 5.8 times (frequencies 40 and 150 kHz) comparing to full-order model application without any alteration of accuracy (less than 0.03 normalized voltage). For impedance method, the simulation time has been decreased 10 times less than using full-order model in frequency range 90–100 kHz while the error of impedance real part remains less than 0.025.
      PubDate: 2017-02-06T02:31:18.978718-05:
      DOI: 10.1002/stc.1994
       
  • New results concerning structural health monitoring technology
           qualification for transfer to space vehicles
    • Authors: Daniela Enciu; Ioan Ursu, Adrian Toader
      Abstract: This article reports the results of recent complex tests on the survival, in view of space applications, of structural health monitoring (SHM) methodology that uses piezo wafer active sensors (PWAS) and the electromechanical impedance spectroscopy (EMIS) method. Successive and then concomitant actions of the harsh conditions of outer space, including extreme temperatures and radiation, were simulated in a laboratory. The basis of the method consists in the fact that the real part of the bonded PWAS impedance spectrum, the so-called EMIS structure signature, follows the resonance behaviour of the structure vibrating under the PWAS excitation and, consequently, the onset and progress of structural damage with fidelity. The tests were conducted on the PWAS separately and aluminium discs with PWAS bonded on them as structural specimens. The conclusion of the tests is that the cumulative impact of severe conditions of temperature and radiation did not result in the decommissioning of the sensors or adhesive, which would have meant that the methodology was compromised. This conclusion occurs as a result of applying two new analysis methods to EMIS signatures. The first method, based on systematic observation of EMIS signatures during tests, makes it possible to distinguish between real damage with a mechanical origin and false damage, which is reversible and caused by the harsh environmental factors. A second method, based on the concept of entropy, shows how to identify mechanical damage at a certain distance from the PWAS. Moreover, an offline analysis of the EMIS “entropy” signatures supports the conclusion that the SHM technology survived the harsh environmental conditions.
      PubDate: 2017-02-03T00:25:42.83407-05:0
      DOI: 10.1002/stc.1992
       
  • Concrete dam deformation prediction model for health monitoring based on
           extreme learning machine
    • Authors: Fei Kang; Jia Liu, Junjie Li, Shouju Li
      Abstract: Structural health monitoring via quantities that can reflect behaviors of concrete dams, like horizontal and vertical displacements, rotations, stresses and strains, seepage, and so forth, is an important method to evaluate operational states of concrete dams correctly and predict the future structural behaviors accurately. Traditionally, statistical model is widely applied in practical engineering for structural health monitoring. In this paper, an extreme learning machine (ELM)-based health monitoring model is proposed for displacement prediction of gravity dams. ELM is one type of feedforward neural networks with a single layer of hidden nodes, where the weights connecting inputs to hidden nodes are randomly assigned. The model can produce good generalization performance and learns faster than networks trained using the back propagation algorithm. The advantages such as easy operating, high prediction accuracy, and fast training speed of the ELM health monitoring model are verified by monitoring data of a real concrete dam. Results are also compared with that of the back propagation neural networks, multiple linear regression, and stepwise regression models for dam health monitoring.
      PubDate: 2017-02-03T00:21:30.603982-05:
      DOI: 10.1002/stc.1997
       
  • A passive electromagnetic eddy current friction damper (PEMECFD):
           Theoretical and analytical modeling
    • Authors: Mohsen Amjadian; Anil K. Agrawal
      Abstract: The focus of this paper is on analytical modeling of a novel type of passive friction damper for seismic hazard mitigation of structures. The proposed seismic damping device, which is termed as passive electromagnetic eddy current friction damper, utilizes a solid-friction mechanism in parallel with an eddy current damping mechanism to maximize the dissipation of input seismic energy through a smooth sliding in the damper. In this passive damper, friction force is produced through magnetic repulsive action between two permanent magnetic sources magnetized in the direction normal to the friction surface, and the eddy current damping force is generated because of the motion of the permanent magnetic sources in the vicinity of a conductor. The friction and eddy current damping parts are able to individually produce ideal rectangular and elliptical hysteresis loops, respectively; which, when combined in the proposed device, are able to accomplish a higher input seismic energy dissipation than that only by the friction mechanism. This damper is implemented on a two-degree-of-freedom system to demonstrate its capability in reducing seismic responses of frame building structures. The numerical results show that the seismic performance of the proposed damper is comparable with that of passive magnetorheological damper of the same force capacity. However, the cost of the device is likely to be quite lesser than that of a magnetorheological damper.
      PubDate: 2017-02-03T00:16:40.968509-05:
      DOI: 10.1002/stc.1978
       
  • Monitoring of masonry historical constructions: 10 years of static
           monitoring of the world's largest oval dome
    • Authors: Rosario Ceravolo; Annunziata De Marinis, Marica L. Pecorelli, Luca Zanotti Fragonara
      Abstract: This paper presents the analyses conducted on the data acquired by the monitoring system of the “Regina Montis Regalis” Basilica of Vicoforte (Italy) in the decade 2004–2014. The Basilica is a building of great historical, architectural, and structural significance, owing its fame to its impressive masonry oval dome, the world's largest of this shape (internal axes of 37.23 by 24.89 m).The dome-drum system of the Basilica has suffered over the years of significant structural problems, partly due to the settlements of the building induced progressively by newly built masses and also to the sliding of the underground. In 1983, concerns over the severe settlements and cracking phenomena affecting the structure prompted the decision to undertake strengthening interventions. A special hooping system, consisting of 56 tie bars, placed around the oval perimeter of the dome, was thus conceived to limit the crack opening.The monitoring system of the Basilica installed in the early 1980s underwent several renovations, and in 2004, its acquisition procedure was automatized. One hundred twelve instruments, consisting of temperature sensors, crackmeters, load cells, pressure cells, wire gauges, hygrometer, piezometers, and hydrometer, are currently installed on the Basilica.This study is primarily focused on data acquired by the crackmeters, the extensometers along the main axes of dome, and the load cells placed at the ends of the tie bars. The main aim of the reported analysis is to evaluate the possible progression of the cracks on the Basilica, and the structural performance of the strengthening interventions put in place in 1985–1987.
      PubDate: 2017-02-03T00:11:21.013083-05:
      DOI: 10.1002/stc.1988
       
  • Structural damage diagnosis with uncertainties quantified using interval
           analysis
    • Authors: Gang Liu; Zhu Mao
      Abstract: The in situ structural assessment by means of structural health monitoring (SHM) has received a great attention in all sorts of civil engineering applications. However, SHM implementations especially damage detections for real-world infrastructures are always overwhelmed with uncertainties of high dimensionality. A nonprobabilistic uncertainty-quantification-enhanced damage diagnosis method is proposed in this study with respect to interval analysis on SHM features. The diagonal elements of the vector auto-regressive model, constructed from the data measurements, are firstly extracted to form a vector, and this vector's Mahalanobis distance between pristine and unknown conditions is used as a damage-sensitive feature. Subsequently, the uncertainty sources, such as measurement inaccuracy and physical variability, are considered as influencing variables. A differential evolution algorithm is thereby introduced to convert the fluctuating interval of those variables into the uncertainty interval of Mahalanobis distance estimation. Finally, inspired by the idea of receiver operating characteristics when probability of detection is available, a modified mathematic metric is defined suited for interval analysis, and area under the modified receiver operating characteristics curve is employed to detect and localize damages. A contrived numerical mass-spring system and a laboratory-scale frame structure are used to validate the proposed framework; and in addition, the damage severity is able to be quantified via a proposed interval distance between pristine and inspection conditions.
      PubDate: 2017-02-03T00:05:41.287762-05:
      DOI: 10.1002/stc.1989
       
  • Radial basis function neural network algorithm for semi-active control of
           base-isolated structures
    • Authors: Agrahara Krishnamoorthy; Shubha Bhat, Dattatreya Bhasari
      Abstract: Curved surface slider (CSS) is considered as an effective isolation device for structures subjected to earthquake ground motions. Due to constant frequency, CSS may encounter a resonance problem when subjected to near-fault earthquake ground motions. To overcome this problem, we propose CSS combined with a control device in this study. The control device consists of variable orifice fluid damper, and its damping coefficient is controlled by a radial basis function-based neural network algorithm. Numerical simulations are performed to evaluate the effectiveness of the proposed technique for only one-directional horizontal seismic excitations without any evaluation concerning the durability of CSSs. The results of the investigation demonstrate that the proposed technique is effective to reduce both the base shear and the sliding displacement of the isolated structure. In addition, the response predicted by the proposed technique is almost similar to the response of isolated structure with passive damper at optimum damping ratio.
      PubDate: 2017-02-03T00:05:30.587509-05:
      DOI: 10.1002/stc.1984
       
  • Seismic resilience timber connection—adoption of shape memory alloy
           tubes as dowels
    • Authors: Haoyu Huang; Wen-Shao Chang
      Abstract: This study investigates a novel timber dowel-type connection system using superelastic shape memory alloy (SMA) bar and tubes as dowels, in order to provide self-centering effect. Double-shear connections with SMA and mild steel dowels were tested under dynamic loadings at different displacement levels. The results showed that SMA dowel-type connections have good self-centering behaviours and can mitigate the residual deformation effectively compared with steel dowel-type connections after excessive deformation; although the steel dowel-type connections present higher strength. These tests reveal that the connection with tube dowels show higher equivalent viscous damping ratio than those use solid bar as tube would allow larger deformation to dissipate energy. To demonstrate application of the benefit of this system, an analytical model of a 3-storey timber framed structure was built for parametric study. The results showed that the structures with conventional dowel-type type connections exhibit large unrecoverable deformation after timber framed structures experience an earthquake. In comparison, those with the connections developed in this project show limited unrecoverable deformation due to the self-centering capacity of the connections.
      PubDate: 2017-02-03T00:00:55.603377-05:
      DOI: 10.1002/stc.1980
       
  • Inertial mass damper for mitigating cable vibration
    • Authors: Lei Lu; Yuan-Feng Duan, Billie F. Spencer, Xilin Lu, Ying Zhou
      Abstract: Stay cables used in cable-stayed bridges are prone to vibration due to their low-inherent damping characteristics. Many methods have been implemented in practice to mitigate such vibration. Recently, negative stiffness dampers have gained attention because of their promising energy dissipation ability. The viscous inertial mass damper (VIMD) has been shown to have properties similar to negative stiffness dampers. This paper examines the potential of the VIMD to enhance the damping, and mitigate the vibration, of stay cables. First, a control-oriented model of the cable is employed to formulate a system level model of the cable–VIMD system for small in-plane motion. After carefully classifying and labeling the mode order, the modal characteristics of the system are analyzed, and the optimal damper parameters for the several lower frequency modes are determined numerically. The results show that the achievable modal damping ratio can be up to nearly an order of magnitude larger than that of the traditional linear viscous damper; note that the optimal parameters of the VIMD are distinct for each mode of interest. These results are further validated through analysis of the cable responses due to the distributed sinusoidal excitation. Finally, a case study is conducted for a cable with a length of 307 m, including the design of practical damper parameters, modal-damping enhancement, and vibration mitigation under wind loads. The results show that the VIMD is a promising practical passive damper that possesses greater energy dissipation capacity than the traditional viscous damper for such cable–damper systems.
      PubDate: 2017-02-02T23:59:51.473176-05:
      DOI: 10.1002/stc.1986
       
  • Detecting structural damage to bridge girders using radar interferometry
           and computational modelling
    • Authors: Maizuar Maizuar; Lihai Zhang, Saeed Miramini, Priyan Mendis, Russell G. Thompson
      Abstract: The process for assessing the condition of a bridge involves continuously monitoring changes to the material properties, support conditions, and system connectivity throughout its life cycle. It is known that the structural integrity of bridges can be monitored by measuring their vibration responses. However, the relationship between frequency changes and structural damage is still not fully understood. This study presents a bridge condition assessment framework which integrates computational modelling and noncontact radar sensor techniques (i.e., IBIS-S) to predict changes in the natural frequencies of a bridge girder as a result of a range of parameters that govern its structural performance (e.g., elastomeric bearing stiffness, concrete compressive stiffness, and crack propagation). Using a prestressed concrete bridge in Australia as a case study, the research outcomes suggest that vibration monitoring using IBIS-S is an efficient way for detecting the degradation of elastomeric bearing stiffness and shear crack propagation in the support areas that can significantly affect the overall structural integrity of a bridge structure. However, frequency measurements have limited capability for detecting the decrease in the material properties of a bridge girder.
      PubDate: 2017-02-02T23:25:29.031281-05:
      DOI: 10.1002/stc.1985
       
  • Control of underground blast induced building vibration by
           shape-memory-alloy rubber bearing (SMARB)
    • Authors: Papiya D. Mondal; Aparna D. Ghosh, Subrata Chakraborty
      Abstract: This paper focuses on the performance of shape-memory-alloy rubber bearings (SMARBs) compared to conventional lead-plug or New-Zealand (N-Z) bearings in control of building vibration due to underground blast induced ground motion (BIGM). The performance is evaluated with regard to maximum acceleration and isolator displacement obtained by nonlinear time history analysis. In doing so the Bouc–Wen's model is used to represent the nonlinear behaviour of the N-Z bearing and the superelastic behaviour of nickel–titanium-based shape-memory alloy is represented by the Graesser–Cozzarelli model. The underground BIGM input is modelled by exponentially decaying function. It is observed that though the N-Z bearing is fairly effective in controlling the structural accelerations due to BIGM without excessive bearing displacements, there remains a problem with the residual bearing displacements. The latter, however, is found to be dealt with very effectively by the SMARB. Furthermore, the procedure to obtain the optimum design parameters of the base isolators under study is obtained by optimizing two mutually conflicting objective functions, that is, the minimization of peak acceleration as well as peak bearing displacement by converting the multiobjective optimization problem to a single composite objective function. The improved and robust control performance of SMARB compared to N-Z bearing is elucidated through numerical study by considering a five-storied shear building frame.
      PubDate: 2017-02-02T23:20:30.575149-05:
      DOI: 10.1002/stc.1983
       
  • Utilization of structural health monitoring in long-span bridges: Case
           studies
    • Authors: Zhen Sun; Zilong Zou, Yufeng Zhang
      Abstract: Structural health monitoring (SHM) of bridges has gained rapid development in the past few years. This paper describes application of SHM on long-span bridges in China, with the aim to illustrate its practical value. A short review of its development and practice is firstly introduced. Three case studies are subsequently presented on utilization of SHM data in engineering practice. In the first case study, a ship collision incident is analyzed using SHM data. An alarm is sent and confirmed when the collision occurred, and mode parameters are identified with GPS measurements to evaluate the bridge condition. In the second case study, damage of expansion joints in a suspension bridge is assessed with girder end displacement measurements. Malfunction of viscous damper is found to correlate with cumulative displacement. The results show that cumulative displacement can be used for condition assessment of expansion joints. In the third case study, the performance of tuned mass dampers is evaluated with wind and vibration measurements before and after tuned mass damper installation. Through explanation of these case studies, the paper illustrates how to distill useful insights from SHM data, which could be instructive for further research in this field.
      PubDate: 2017-01-06T05:36:01.302483-05:
      DOI: 10.1002/stc.1979
       
  • Eulerian-based virtual visual sensors to measure dynamic displacements of
           structures
    • Authors: Ali Shariati; Thomas Schumacher
      Abstract: Vibration measurements provide useful information about a structural system's dynamic characteristics and are used in many fields of science and engineering. Here, we present an alternative noncontact approach to measure dynamic displacements of structural systems using digital videos. The concept is that intensity measured at a pixel with a fixed (or Eulerian) coordinate in a digital video can be regarded as a virtual visual sensor. The pixels in the vicinity of the boundary of a vibrating structural element contain useful frequency information, which we have been able to demonstrate in earlier studies. Our ultimate goal, however, is to be able to compute dynamic displacements, i.e., actual displacement amplitudes in the time domain. In order to achieve that, we introduce the use of simple black-and-white targets that are mounted on locations of interest on the structure. By using these targets, intensity can be directly related to displacement, turning a video camera into a simple, computationally inexpensive, and accurate displacement sensor with notably low signal-to-noise ratio. We show that subpixel accuracy with levels comparable to computationally expensive block matching algorithms can be achieved using the proposed targets. Our methodology can be used for laboratory experiments, on real structures, and additionally, we see educational opportunities in K-12 classroom. In this paper, we introduce the concept and theory of the proposed methodology, present and discuss a laboratory experiment to evaluate the accuracy of the proposed black-and-white targets, and discuss the results from a field test of an in-service bridge.
      PubDate: 2016-12-23T01:26:16.847281-05:
      DOI: 10.1002/stc.1977
       
  • Performance of tuned tandem mass dampers for structures under the ground
           acceleration
    • Authors: Yunzhi Yang; Chunxiang Li
      Abstract: It is widely acknowledged that the tuned mass damper (TMD) is one of the most effective and simplest passive control devices, but its limited control performance is still a troubling problem. In order to surmount the shortage of TMD, the tuned tandem mass dampers (referred herein to as TTMD) have been proposed for mitigating the undesirable oscillation of structures under the ground acceleration. Based on the formulation of the mode-generalized system in the specific vibration mode being controlled, the analytical expression is then derived for the dynamic magnification factor of the structure furnished with a TTMD. The optimum criterion can thereby be defined as minimization of the minimum values of the maximum dynamic magnification factor with a set of optimization variables embedded so as to give full play to the control device potential. The optimization implementation of TTMD is carried out by the MATLAB-based coding and debugging. For the purpose of a mutual authentication to the optimization results, three metaheuristic algorithms, namely, genetic algorithm, particle swarm optimization, and simulated annealing, are concurrently taken into consideration. Results demonstrate that the proposed TTMD endows with the superior stroke performance with respect to TMD.
      PubDate: 2016-12-22T00:51:05.605001-05:
      DOI: 10.1002/stc.1974
       
  • Using water hammer to enhance the detection of stiffness changes on an
           out-of-round pipe with distributed optical-fibre sensing
    • Authors: Leslie Wong; Kenneth Lim, Wing Kong Chiu, Jayantha Kodikara, Nabil Chowdhury
      Abstract: Over the last few decades, distributed optical fibre sensor (DOFS) has been introduced to monitor the structural health of water pipelines. Most of the previous studies show that DOFS is very effective as a static measurement and monitoring platform. However, there is still a lack of research being done using DOFS to monitor the dynamic response of the pipeline. This paper will first demonstrate the dynamic capability of optical frequency domain reflectometry-based DOFS on a pipe. To be specific, the primary monitoring work is conducted on an out-of-round plastic pipe subjected to water hammer. It is important to monitor the dynamic response of the pipe as it is well known that water hammer can occur in any pressurised pipeline system due to changes in the operating conditions. The ability to detect local stiffness irregularity on the noncircular pipe subjected to water hammer is also demonstrated. The result shows that the presence of the local stiffness change is accentuated when the pipe is subjected to water hammer. The dynamic capability of DOFS facilitates the application of water hammer as a stimulus and hence shows the potential to enhance pipeline health monitoring.
      PubDate: 2016-12-21T23:41:07.817743-05:
      DOI: 10.1002/stc.1975
       
  • Shake table real-time hybrid simulation techniques for the performance
           evaluation of buildings with inter-story isolation
    • Authors: Ruiyang Zhang; Brian M. Phillips, Shun Taniguchi, Masahiro Ikenaga, Kohju Ikago
      Abstract: Interstory isolation systems have recently gained popularity as an alternative for seismic protection, especially in densely populated areas. In inter-story isolation, the isolation system is incorporated between stories instead of the base of the structure. Installing inter-story isolation is simple, inexpensive, and disruption free in retrofit applications. Benefits include nominally independent structural systems where the accelerations of the added floors are reduced when compared to a conventional structural system. Furthermore, the base shear demand on the total structure is not significantly increased. Practical applications of inter-story isolation have appeared in the United States, Japan, and China, and likewise new design validation techniques are needed to parallel growing interest. Real-time hybrid simulation (RTHS) offers an alternative to investigate the performance of buildings with inter-story isolation. Shake tables, standard equipment in many laboratories, are capable of providing the interface boundary conditions necessary for this application of RTHS. The substructure below the isolation layer can be simulated numerically while the superstructure above the isolation layer can be tested experimentally. This configuration provides a high-fidelity representation of the nonlinearities in the isolation layer, including any supplemental damping devices. This research investigates the seismic performance of a 14-story building with inter-story isolation. A model-based acceleration-tracking approach is adopted to control the shake table, exhibiting good offline and online acceleration tracking performance. The proposed methods demonstrate that RTHS is an accurate and reliable means to investigate buildings with inter-story isolation, including new configurations and supplemental control approaches.
      PubDate: 2016-12-21T03:25:37.460926-05:
      DOI: 10.1002/stc.1971
       
  • Damage detection in elastic properties of masonry bridges using coda wave
           interferometry
    • Authors: Marcello Serra; Gaetano Festa, Maurizio Vassallo, Aldo Zollo, Antonino Quattrone, Rosario Ceravolo
      Abstract: Structures may be subjected to damage and deterioration over different timescales, and monitoring their health status may allow to perform maintenance actions before the functionality limit is reached. Masonry arch bridges, in particular, are sensitive to the bearings loss produced by scour of the streambed soil at the pier foundations. In this study, we measured the changes in the elastic properties of a 1:2 scaled model of a masonry arch bridge built in the laboratory to study the evolution of the damage mechanism related to the application of foundation movements. Specifically, the bridge is realized to model the effect of erosion of the ground underneath the central pier. We analysed the accelerometric records acquired along the structure generated by a sledgehammer hitting the bridge walls. We used the method of coda wave interferometry to detect the changes in the elastic properties of the medium. After selecting the specific frequency band exciting coda waves, we progressively measured the time lag between signals acquired in the intact and two damaged stages of the bridge for each source–receiver couple, and we fit the data to get the relative wave velocity changes. We found that the average relative velocity changes for the two damaged steps are Δv/v = −5.08 ± 0.08% and Δv/v = −8.2 ± 0.6%, consistently measured at all the analysed source–receiver couples. These values correspond to an average estimation of the velocity changes occurred within the structure, because the associated wavelengths are comparable with the bridge size and the damage is spread over a large portion of the structure.
      PubDate: 2016-12-20T03:55:48.31577-05:0
      DOI: 10.1002/stc.1976
       
  • Crack propagation monitoring using an image deformation approach
    • Authors: D. Dias-da-Costa; J. Valença, E. Júlio, H. Araújo
      Abstract: An image deformation method is herein proposed to monitor the crack propagation in structures. The proposed approach is based on a computational algorithm that uses displacements measured by photogrammetry or image correlation to generate a virtual image of the surface, from an initial input to any given stage of analysis. This virtual image is then compared with the real image of the specimen to identify any discontinuities that appeared or evolved during the monitored period. The procedure was experimentally validated in the characterisation of crack propagation in concrete specimens. When compared with other image processing techniques, for instance, based on edge detectors, the image deformation approach showed insensitiveness to any discontinuity previously existing on the surface, such as cracks, stains, voids, or shadows, and did not require any specific surface treatments or lighting conditions. With this approach, the global crack maps could be extracted from the surface of the structure and extremely small changes occurring within a given time interval could be characterised, such as the movement associated with the opening of cracks. It is highlighted that the proposed procedure is general and therefore applicable to detect and characterise surface discontinuities in different materials and test set-ups.
      PubDate: 2016-12-20T03:27:06.88695-05:0
      DOI: 10.1002/stc.1973
       
  • Damage detection in beam and truss structures by the inverse analysis of
           the static response due to moving loads
    • Authors: Nadir Boumechra
      Abstract: The detection and the localization of damages in a bridge have been always one of the major concerns of infrastructure managers, engineers, and researchers. In addition to the dynamic techniques that were well imposed in the diagnosis of bridges, several static methods have been developed. The idea of this work is to exploit the measurement results about a bridge deflection submitted to a moving load. By using the displacements response, important data about the displacement of a structural point could be gathered. When the structure's geometry and the material characteristics are known, a finite element model, supposed to be the most similar, could be developed. The numerical structural model and the static displacements data are used to develop an equilibrium equations system where unknowns are the possible stiffness changes in the finite element model. Thus, the global stiffness matrix of the studied structure is a polynomial matrix. The equilibrium equations system is a static inverse problem requiring resolution. To facilitate the mathematical development, the inverse of the global stiffness matrix is expressed by a Neumann series. Then, the resolution of the system is done by a code developed in Matlab. To confirm the good convergence of the developed mathematical method, numerical tests are carried out by considering beams and a 3D truss bridge subjected to a moving load. Thereafter, an analysis concerning the influence of the noise in the displacements data on the accuracy of the inverse analysis and the convergence of the results is made. It has been shown that the large number of data reduces the noises effect and the damages detection can be ensured.
      PubDate: 2016-12-16T02:25:49.402413-05:
      DOI: 10.1002/stc.1972
       
  • Structural time-dependent reliability assessment of the vibration active
           control system with unknown-but-bounded uncertainties
    • Authors: Lei Wang; Xiaojun Wang, Yunlong Li, Guiping Lin, Zhiping Qiu
      Abstract: The active control system for structural vibration is extremely sensitive to the parametric uncertainty so that more and more concerns of its reliability estimation have been given recently. In view of the insufficiency of the uncertainty information in practical engineering, a non-probabilistic time-dependent reliability method that combines the active vibration control theory with interval analysis is proposed in this paper to effectively estimate the dynamic safety of the controlled structures, in which circumstances the unknown-but-bounded uncertainties in structural parameters are considered. The uncertain structural responses based on the closed-loop control are firstly analyzed and embodied by the interval process model. By virtue of the first-passage theory, an integral procedure of non-probabilistic time-dependent reliability analysis of the active control system for structural vibration is then conducted. Two engineering examples and one experimental application are eventually presented to demonstrate the validity and applicability of the methodology developed.
      PubDate: 2016-12-02T01:47:24.385306-05:
      DOI: 10.1002/stc.1965
       
  • Experimental image and range scanner datasets fusion in SHM for
           displacement detection
    • Authors: Javier Rivera-Castillo; Wendy Flores-Fuentes, Moisés Rivas-López, Oleg Sergiyenko, Felix F. Gonzalez-Navarro, Julio C. Rodríguez-Quiñonez, Daniel Hernández-Balbuena, Lars Lindner, Luis C. Básaca-Preciado
      Abstract: Optical images and signals can be used to detect displacement in civil engineering structures. This paper presents a technical experimentation of a vision-based technology and artificial intelligence algorithms methodology for structural health monitoring of new and aging structures, by a noncontact and nondestructive system. The experimental study emphasis is on the outdoor urban environment, by the detection of spatial coordinate displacement on the structures, in order to perform a damage assessment. Also, the experimental study contains both theoretical and experimental aspects of the fusion of image and range scanner datasets created using intelligent algorithms. A camera and an optical scanning system were used to generate high resolution and quality images for 2D imaging, and 3D accuracy range data from optoelectronic sensor signals. Scans at a specific area of an engineering structure were performed to measure spatial coordinates displacements, successfully verifying the effectiveness and the robustness of the proposed non-contact and non-destructive monitoring approach.
      PubDate: 2016-12-02T01:12:21.63409-05:0
      DOI: 10.1002/stc.1967
       
  • Laboratory validation of buried piezoelectric scour sensing rods
    • Authors: Faezeh Azhari; Kenneth J. Loh
      Abstract: Scour, or the erosion of soil and sediments near bridge piers and abutments, accounts for the majority of overwater bridge failures. This study focuses on evaluating the use of a driven piezoelectric scour sensing rod, where the real-time dynamics of the voltage response of the sensing rod is used to determine scour depths using the inverse relation between natural frequency and the rod's exposed length. A poly (vinylidene fluoride) polymer strip forms the main sensing component of this prototype sensor. After confirming the viability of the sensing concept through various idealized tests, the response of the sensors was studied in scour conditions simulated in a laboratory flume. The sensors were driven into the soil surrounding a cylindrical pier. As the scour hole evolved, the exposed length of the sensors changed, causing the measured natural frequencies to also vary. Scour depth at each sensor location was determined using a simple cantilever beam eigenfrequency analysis where the soil support fixity was modeled with a rotational spring. The results were promising in that the sensors were capable of detecting scour depths and the scour hole topography with reasonable accuracy. As is the case with other rod-like scour sensors, vulnerability to debris and installation difficulties are some of the limitations that need to be addressed in future real-world implementations.
      PubDate: 2016-12-02T01:03:26.821367-05:
      DOI: 10.1002/stc.1969
       
  • Optimal sensor placement for damage detection of bridges subject to ship
           collision
    • Authors: Y.L. Guo; Y.Q. Ni, S.K. Chen
      Abstract: Ship collisions threaten the safety of bridges over navigable waterways in modern times. Postcollision damage and condition assessment is thus of significant importance for decision making on whether closure of bridge to traffic is necessary and for planning the consequent bridge strengthening or retrofitting. Online structural health monitoring systems provide a unique approach to monitor bridge responses during ship collisions and detect the structural damage. The damage information contained in the monitoring data, which is critical for damage detection, however, is largely dependent on the sensor layout. In this paper, an optimal sensor placement method targeting postcollision damage detection of bridges is proposed for selecting the optimal sensor set so that the measured data are most informative for damage detection. The sensor configuration is optimized by a multi-objective optimization algorithm, which simultaneously minimizes the information entropy index for each possible ship-bridge collision scenario. One advantage of the proposed method is that it can handle the uncertainty of ship collision position. It also guarantees a redundancy of sensors for the most informative regions and leaves a certain freedom to determine the critical elements for monitoring. The proposed method is applicable in practice to determine the sensor placement, prior to field testing, with the intention of identifying postcollision damage. The cable-stayed Ting Kau bridge in Hong Kong is employed to demonstrate the feasibility and effectiveness of the proposed method.
      PubDate: 2016-11-28T03:30:34.187252-05:
      DOI: 10.1002/stc.1963
       
  • 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
           detection
    • 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
           meta-method
    • 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
           excitation
    • 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
       
  • Structural displacement measurements using DC coupled radar with active
           transponder
    • Authors: Shanyue Guan; Jennifer A. Rice, Changzhi Li, Yiran Li, Guochao Wang
      Abstract: Continuous wave (CW) radar sensors are a promising technology for structural displacement measurement. However, the commonly employed passive backscattering measurement configuration has some limitations for low-power applications of CW radar. To improve displacement measurement performance using the low-power CW radar, an active transponder configuration is introduced. Compared with passive backscattering, the active transponder configuration is capable of increasing the radar's signal power, thereby increasing the signal to noise ratio for more accurate displacement measurement. A series of laboratory experiments to demonstrate the performance of the transponder configuration was conducted, and the experimental results were compared with the results of using the backscattering configuration. The investigation revealed that the signal improvement provided by the transponder is a function of the distance between the transponder and the radar. In addition, a full-scale bridge test with the active transponder configuration was conducted to verify the improved performance. An oblique angle test using the transponder was conducted in the laboratory to demonstrate the potential for flexible installation strategies when deploying the radar/transponder pair for bridge displacement measurements. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-06T02:46:07.386326-05:
      DOI: 10.1002/stc.1909
       
  • Estimation of wind loads on a tall building by an inverse method
    • 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 system
    • Authors: Byung Kwan Oh; Jin Woo Hwang, Se Woon Choi, Yousok Kim, Tongjun Cho, Hyo Seon Park
      Abstract: In this paper, a dynamic displacements-based model updating method using a motion capture system (MCS) is proposed. The dynamic characteristics from MCS are used to find the parameters that minimize the difference between updated model and direct measurement. Using a multi-objective optimization algorithm of non-dominated sorting genetic algorithm-II, the number of objective functions for model updating is set to the same number of modes under consideration, and all the objective function are simultaneously minimized. To consider the contribution of each mode on model updating and to avoid biased results, a rule for weighting of solutions associated to each mode based on modal participation factors is suggested and tested. Using a free vibration experimental test of a three-story shear model, the performance of model updating method is verified by the comparison of the dynamics characteristics between the updated model and direct measurement by MCS. In addition, time histories of displacements from the updated model are compared with the direct measurement. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-21T01:00:44.257955-05:
      DOI: 10.1002/stc.1904
       
  • A baseline-free and non-contact method for detection and imaging of
           structural damage using 3D laser vibrometry
    • Authors: P. Aryan; A. Kotousov, C. T. Ng, B. S. Cazzolato
      Abstract: Detection and characterisation of structural damage using guided waves is very promising technique in non-destructive testing and structural health monitoring systems. Because of their simplicity and low cost, current techniques normally utilise traditional piezo-electric or optical fibre sensors to capture a directional scattered field from a defect or damaged area. However, the practical implementation of these techniques usually requires an extensive preliminary study in order to identify a suitable location and polarisation of the sensors, as well as determine the optimal parameters for wave excitation, which vary depending on the size and type of damage and structure. Recent advances in 3D laser vibrometry provide an opportunity to avoid many of the restrictions and limitations associated with traditional (1D) sensing systems by capturing the transient 3D displacement/velocity fields rather than the displacement/strain along a single axis and limited to a small number of discrete locations. Using 3D laser vibrometry, this paper suggests a non-contact, baseline-free method for imaging structural defects such as corrosion spots, cracks and dents as well as delamination damage. It focuses on the mode conversion effects and investigates the sensitivity of the in-plane and out-of-plane scattered fields in relation to the presence of common defects. The experimental measurements are presented in terms of the root mean square (RMS) values of the velocity field. The outcomes of the present study can help in a number of ways, including selecting an appropriate strategy for defect detection using guided wave techniques. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-10T03:22:06.282057-05:
      DOI: 10.1002/stc.1894
       
  • Damage detection of multi-story shear buildings due to earthquakes by
           model updating method
    • Authors: J.Y. Zhang; T. Aoki
      Abstract: In this paper, we present a novel model updating method for damage detection of multi-story shear buildings during severe earthquakes. The story stiffnesses are explicitly presented in an incremental manner; this enables a simple and robust algorithm for the purpose of identification of the story stiffnesses. The estimated modal data, including natural frequencies and mode shapes of lower modes, are used in the proposed algorithm; moreover, sensitivity analysis of natural circular frequencies is incorporated to reduce possible errors. The story stiffnesses are identified by an iterative algorithm, and the window shift technique is adopted to present change of the story stiffness due to damages in the buildings during earthquakes. Numerical examples demonstrate that the proposed method is of high accuracy, even when the recorded responses are polluted by a relatively high level of (white) noises. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-10T03:15:36.476483-05:
      DOI: 10.1002/stc.1895
       
  • A leverage-type stiffness controllable mass damper for vibration
           mitigation of structures
    • 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
       
  • Compressive sensing based structural damage detection and localization
           using theoretical and metaheuristic statistics
    • Authors: Ruigen Yao; Shamim N. Pakzad, Parvathinathan Venkitasubramaniam
      Abstract: Accurate structural damage identification calls for dense sensor networks, which are becoming more feasible as the price of electronic sensing systems reduces. To transmit and process data from all nodes of a dense network is a computationally expensive BIG DATA problem; therefore scalable algorithms are needed so that inferences about the current state of the structure can be made efficiently. In this paper, an iterative spatial compressive sensing scheme for damage existence identification and localization is proposed and investigated. At each iteration, damage existence is identified from randomly collected sparse samples and damage localization is iteratively detected via sensing–processing cycles with metaheuristic sampling distribution updating. Specifically, simulated annealing and ant colony analogy are used for guidance in future selection of sensing locations. This framework is subsequently validated by numerical and experimental implementations for gusset plate crack identification. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-06T02:35:40.21143-05:0
      DOI: 10.1002/stc.1881
       
  • Simultaneous identification of stiffness, mass, and damping using an
           on-line model updating approach
    • Authors: Xing-Huai Huang; Shirley Dyke, Zhuoxiong Sun, Zhao-Dong Xu
      Abstract: The development of damage identification methods that enable rapid implementation holds great promise for assessing structural integrity to avoid further damage or catastrophic failure. Here, an on-line model updating approach is proposed to rapidly and simultaneously identify the mass, stiffness, and damping properties of a structural model. The proposed approach facilitates identification of these unknown parameters using two steps: first, energy equilibrium equations are used to establish a relationship between structural energy and unknown parameters; second, the Kalman filter is adopted to obtain the unknown parameters in a short period of time. Numerical verification is conducted on a 158-degree-of-freedom truss model with 324 unknown parameters based on a real-world structure. The results indicate that the proposed approach can simultaneously identify the model parameters for the mass, stiffness, and damping of both the damaged and undamaged structures online, and also can effectively identify the stiffness damage and mass change, even in an environment with noise. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-06-03T02:05:45.606515-05:
      DOI: 10.1002/stc.1892
       
  • Traffic volume estimation in a cable-stayed bridge using dynamic responses
           acquired in the structural health monitoring
    • Authors: Kaiwan Wattana; Mayuko Nishio
      Abstract: This paper presents the traffic volume estimation by constructing a statistical model using dynamic response data acquired by a structural health monitoring system installed on an in-service cable-stayed bridge. The structural health monitoring system consists of various sensors, including accelerometers, tilt sensors, temperature sensors, and the vehicle counting system. In this paper, the correlations between the response features from dynamic data, peak frequencies and amplitudes of responses, and the temperature and the traffic volume were firstly investigated. The results revealed that the traffic volume was a dominant factor that influenced on variances of the extracted features, while the temperature showed low effects on them in the target bridge. Some of the response features that showed high correlations were then selected for constructing a linear regression model to estimate the total traffic volume per 5 min. The constructed model then showed the accurate fitting performance to the data, and it was also capable of predicting the traffic volume on the bridge. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-05-31T23:50:44.522429-05:
      DOI: 10.1002/stc.1890
       
 
 
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