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ENERGY (183 journals)                 | Last

Showing 1 - 200 of 406 Journals sorted alphabetically
ActaEnergetica     Open Access  
Advances in Building Energy Research     Hybrid Journal   (Followers: 9)
Advances in Energy and Power     Open Access   (Followers: 8)
Advances in High Energy Physics     Open Access   (Followers: 20)
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: 7)
Applied Solar Energy     Hybrid Journal   (Followers: 15)
Archives of Thermodynamics     Open Access   (Followers: 7)
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  
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: 23)
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: 25)
Energy & Environment     Hybrid Journal   (Followers: 18)
Energy & Fuels     Full-text available via subscription   (Followers: 27)
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: 19)
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: 5)
Energy Science & Engineering     Open Access   (Followers: 3)
Energy Science and Technology     Open Access   (Followers: 11)
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: 5)
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: 3)
IEA Natural Gas Information     Full-text available via subscription   (Followers: 3)
IEEE Power and Energy     Full-text available via subscription   (Followers: 25)
IEEE Transactions on Energy Conversion     Hybrid Journal   (Followers: 12)
IEEE Transactions on Nuclear Science     Hybrid Journal   (Followers: 9)
IEEE Transactions on Power Systems     Hybrid Journal   (Followers: 27)
IET Power Electronics     Hybrid Journal   (Followers: 29)
Ingeniería Energética     Open Access  
Innovations : Technology, Governance, Globalization     Hybrid Journal   (Followers: 12)
International Journal of Alternative Propulsion     Hybrid Journal   (Followers: 5)
International Journal of Ambient Energy     Hybrid Journal   (Followers: 1)
International Journal of Applied Power Engineering     Open Access   (Followers: 4)
International Journal of Clean Coal and Energy     Open Access   (Followers: 5)
International Journal of Coal Science & Technology     Open Access   (Followers: 1)
International Journal of Electric and Hybrid Vehicles     Hybrid Journal   (Followers: 9)
International Journal of Emerging Electric Power Systems     Hybrid Journal   (Followers: 6)
International Journal of Energy and Environmental Engineering     Open Access   (Followers: 3)
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: 8)
Journal of Alternate Energy Sources & Technologies     Full-text available via subscription  
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 6)
Journal of China Coal Society     Open Access  
Journal of 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: 3)
Journal of Ocean Engineering and Marine Energy     Hybrid Journal   (Followers: 2)
Journal of Physical Chemistry C     Full-text available via subscription   (Followers: 30)
Journal of Power Electronics & Power Systems     Full-text available via subscription   (Followers: 9)
Journal of Radiological Protection     Full-text available via subscription   (Followers: 4)
Journal of Renewable Energy     Open Access   (Followers: 7)
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: 6)
Nigerian Journal of Technological Research     Full-text available via subscription   (Followers: 1)
Nuclear Data Sheets     Full-text available via subscription  
Nuclear Engineering and Design     Hybrid Journal   (Followers: 13)
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: 12)
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)
Protection and Control of Modern Power Systems     Open Access  
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: 8)
Solar Energy     Hybrid Journal   (Followers: 21)
Solar Energy Materials and Solar Cells     Hybrid Journal   (Followers: 34)
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: 8)
Surface Science Reports     Full-text available via subscription   (Followers: 13)
Sustainable Energy     Open Access   (Followers: 2)
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]   [8 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  [1583 journals]
  • Frequency-selective surface-based chipless passive RFID sensor for
           detecting damage location
    • Authors: MD Imdul Reza Shishir; Seongcheol Mun, Hyun-Chan Kim, Jeong Woong Kim, Jaehwan Kim
      Abstract: Various types of wireless sensor systems are used for structural health monitoring. Especially, chipless wireless sensors are useful in harsh environmental conditions of high temperature and toxic chemicals. This paper reports a chipless passive structural health monitoring sensor made with frequency-selective surface (FSS) array for detecting damage location. FSS is a kind of microwave meta-material antenna that is selective by its electromagnetic characteristics associated with geometrical shape and electrical impedance. An FSS-array-based wireless sensor was made on a flexible substrate that can be easily attached to arbitrary structures. When microwaves are applied to the FSS via a single horn antenna, the sensor senses its reflection changes, and by scanning the horn antenna, the location of damage is detected. Design, fabrication, and characterization of cross-type FSS array are carried out, and a computer simulation is performed for comparison.
      PubDate: 2017-04-27T12:13:20.033389-05:
      DOI: 10.1002/stc.2028
  • Wireless structural control using multi-step TDMA communication patterning
           bandwidth allocation
    • Authors: Benjamin D. Winter; R. Andrew Swartz
      Abstract: As the number of sensors in a control network grows, it becomes increasingly difficult to transmit all sensor data during a single control step over the fixed wireless bandwidth. Because control force calculations rely on accurate state measurements or estimates, the use of staggered data communication may become necessary. It is not uncommon that a single sensor may be the only measurement source for an important section of a structure. This paper presents a means of selecting and evaluating different communication group sizes and wireless unit combinations for staggered communication that still provide information for highly accurate state estimates. Within each wireless unit, multiple estimator gains are stored on-board to perform state-estimation calculations using staggered data that may be received from different combinations of units. It is found that, in staggered communication schemes, state estimation and control performance are affected by the network topology used at each time step with some sensor combinations providing more useful information than others. Sensor placement theory is used to form sensor groups that provide consistently high-quality output information to the network over multiple time steps, so as to strategically report data from all sensors.
      PubDate: 2017-04-27T12:03:33.227784-05:
      DOI: 10.1002/stc.2025
  • Pipeline internal corrosion monitoring based on distributed strain
           measurement technique
    • Authors: Tao Jiang; Liang Ren, Zi-guang Jia, Dong-sheng Li, Hong-nan Li
      Abstract: Pipeline corrosion is an important issue that threatens the pipeline safety operation; therefore, the corrosion monitoring is essential. Based on the optical frequency domain reflectometry technology, which features distributed strain measurement with high resolution and high precision, a new method of pipeline internal corrosion monitoring is proposed to simultaneously locate corrosion and to evaluate corrosion severity. To verify the effectiveness and accuracy of this method, a series of tests were conducted including uniform corrosion test and local corrosion tests. These test results demonstrate that the corrosion location and corrosion severity evaluation can be achieved via the proposed distributed strain measurement, providing a valuable approach for pipeline corrosion monitoring.
      PubDate: 2017-04-26T02:51:22.994458-05:
      DOI: 10.1002/stc.2016
  • Fiber optic health monitoring and temperature behavior of bridge in cold
    • Authors: Feng Xiao; J. Leroy Hulsey, Radhakrishnan Balasubramanian
      Abstract: The objectives of this research are (a) to establish a structural health monitoring system for bridge safety evaluation that is suitable for cold, remote regions and (b) to identify the bridge responses under variations in temperature. To achieve this, fiber optic sensors with temperature compensation were selected that were suitable for cold regions. This technique allows monitoring equipment to operate far from the sensor installation site, which avoids exposing much of the equipment to extremely cold temperatures and makes a power supply more accessible. The bridge temperature behavior is studied based on the real-time field measurement data, and the relationship between the thermal loading and the bridge response is presented.
      PubDate: 2017-04-17T02:27:16.265387-05:
      DOI: 10.1002/stc.2020
  • Issue Information
    • Abstract: No abstract is available for this article.
      PubDate: 2017-04-17T01:09:30.235595-05:
      DOI: 10.1002/stc.1942
  • Obituary
    • PubDate: 2017-04-17T01:09:26.48057-05:0
      DOI: 10.1002/stc.2034
  • Seismic vibration and damage control of high-rise structures with the
           implementation of a pendulum-type nontraditional tuned mass damper
    • Authors: Ping Xiang; Akira Nishitani, Minger Wu
      Abstract: To improve seismic resilience and sustainability of structures, a pendulum-type nontraditional tuned mass damper (PNTTMD) system with re-centering mechanism is proposed for high-rise structures with nonnegligible bending deformation involved. This proposal is motivated by the self-centering behavior of structural components in ancient structures, for example, Greek tower or pagodas, with the assistance of gravity. Analytic formulae employing the stability maximization criterion for optimum design of the PNTTMD are derived, where the rotational angle of the roof is considered. Satisfactory vibration and damage control effects of the PNTTMD system are verified through experimental and numerical investigations.
      PubDate: 2017-04-12T04:37:08.409864-05:
      DOI: 10.1002/stc.2022
  • Thermally modulated shape memory alloy friction pendulum (tmSMA-FP) for
           substantial near-fault earthquake structure protection
    • Authors: Sourav Gur; George N. Frantziskonis, Sudib K. Mishra
      Abstract: Vibration control of structures under near-fault earthquakes by employing a friction pendulum supplemented with thermally modulated shape memory alloy (SMA) springs as damper system is studied. Temperature modulation of the SMA spring during the earthquake effectively alters its hysteretic energy dissipation capacity and thereby the control efficiency of the isolation system. The response of a structure with the isolation system is evaluated through nonlinear dynamic time-history analysis under a set of recorded near-fault ground motions. Through temperature modulation that effectively yields a large SMA hysteretic energy dissipation, the hybrid friction pendulum system with SMA temperature modulation shows enormous control efficiency. A parametric study reveals that under a wide range of conditions, the thermally modulated SMA friction pendulum isolation system shows improved control efficiency over conventional friction pendulum and SMA friction pendulum isolation systems. Further, the temperature-tuned SMA hysteresis loops substantially suppress the high frequency components of earthquake motions, thus reducing the possibility of damage to the structure.
      PubDate: 2017-04-12T04:36:46.79472-05:0
      DOI: 10.1002/stc.2021
  • Equivalent force control combined with adaptive polynomial-based forward
           prediction for real-time hybrid simulation
    • Authors: Huimeng Zhou; David J. Wagg, Mengning Li
      Abstract: The equivalent force control method uses feedback control to replace numerical iteration and solve the nonlinear equation in a real-time hybrid simulation via the implicit integration method. During the real-time hybrid simulation, a time delay typically reduces the accuracy of the test results and can even make the system unstable. The outer-loop controller of the equivalent force control method can eliminate the effect of a small time delay. However, when the actuator has a large delay, the accuracy of the test results is reduced. The adaptive forward prediction method offers a solution to this problem. Thus, in this paper, the adaptive polynomial-based forward prediction algorithm is combined with equivalent force control to improve the test accuracy and stability. The new method is shown to give good stability properties for a specimen with nonlinear stiffness by analyzing the location of the poles of the discrete transfer system. Simulations with linear and nonlinear specimens are then presented to demonstrate the effectiveness of this method. Finally, experimental results with a linear stiffness specimen and a magneto-rheological damper are used to demonstrate that this method has better accuracy than the equivalent force control method with nonadaptive delay compensation.
      PubDate: 2017-04-10T01:37:12.070689-05:
      DOI: 10.1002/stc.2018
  • Early detection of anomalies in dam performance: A methodology based on
           boosted regression trees
    • Authors: Fernando Salazar; Miguel Ángel Toledo, José Manuel González, Eugenio Oñate
      Abstract: The advances in information and communication technologies led to a general trend towards the availability of more detailed information on dam behaviour. This allows applying advanced data-based algorithms in its analysis, which has been reflected in an increasing interest in the field. However, most of the related literature is limited to the evaluation of model prediction accuracy, whereas the ulterior objective of data analysis is dam safety assessment. In this work, a machine-learning algorithm (boosted regression trees) is the core of a methodology for early detection of anomalies. It also includes a criterion to determine whether certain discrepancy between predictions and observations is normal, a procedure to compute a realistic estimate of the model accuracy, and an original approach to identify extraordinary load combinations. The performance of causal and noncausal models is assessed in terms of their ability to detect different types of anomalies, which were artificially introduced on reference time series generated with a numerical model of a 100-m-high arch dam. The final approach was implemented in an online application to visualise the results in an intuitive way to support decision making.
      PubDate: 2017-04-07T03:57:06.418752-05:
      DOI: 10.1002/stc.2012
  • Quasi-OCVT technique for response-only experimental modal analysis of
           beam-like structures
    • Authors: Jianfeng Zhong; Shuncong Zhong, Qiukun Zhang
      Abstract: An optical measurement system, which is capable of vibration measurement and response-only experimental modal analysis for beam-like structures, is reported by taking the concept of 2-dimensional optical coherence vibration tomography technique. In the proposed approach, it requires only quasi-interferogram fringe patterns as sensors and a high-speed camera as a detector. Experimental results of beam-like structures subjected to swept and harmonic excitations are demonstrated. The key advantage of the proposed method is the high spatial and temporal resolution with simultaneously measuring the absolute displacement of multiple points along the beam-like structures without point-by-point optical scanning. Without any vibration excitation information, the quasi-optical coherence vibration tomography technique system can capture structural modal parameters. Therefore, it is a response-only experimental modal analysis method, making it attractive for the structural health monitoring applications in the multiple-point measurement of real engineering structures with the absence of vibration input information.
      PubDate: 2017-03-30T04:25:57.321399-05:
      DOI: 10.1002/stc.2017
  • Method for assessing beam column joints in RC structures using
           photogrammetric computer vision
    • Authors: J. Valença; R.N.F. Carmo
      Abstract: The response of beam column joints is fundamental for structural analysis of reinforcement concrete frames, particularly, when subjected to dynamic actions. Monitoring the key parameters of those joints is essential to perform a detailed analysis of the structure. These are often difficult to obtain, and only a few sections in critical regions are assessed. High-end technologies can bring huge advantages in such measurements. Methods based on computer vision have been applied to monitoring reinforced concrete structures with excellent results, considering the accuracy achieved and the large quantity of information recorded.In this paper, a new method, named “Photo-Node,” based on photogrammetry and image processing is presented. Photo-Node is a noncontact method used to directly monitoring concrete surfaces, developed to measure the relevant physical parameters of reinforcement concrete beam column joints during experimental tests. The method addresses several postprocessing features to evaluate joint rotation, joint distortion, principal directions and stresses, cracks pattern, and load path. Additionally, the critical sections of the beam, that is, the region adjacent to the joint where the formation of the plastic hinge is expected, can be also evaluated. Photo-Node provides a large amount of data, which can be processed to properly assess the joints behaviour. The degree of discretisation achieved enables to identify behaviours impossible to detect using traditional and less discretised approaches. The application of the method showed promising and accurate results, proving to be an efficient and a wide-ranging tool to be used in experimental programs.
      PubDate: 2017-03-30T03:51:10.628308-05:
      DOI: 10.1002/stc.2013
  • Negative stiffness device for seismic protection of smart base isolated
           benchmark building
    • Authors: Tong Sun; Zhilu Lai, Satish Nagarajaiah, Hong-Nan Li
      Abstract: This paper presents a novel negative stiffness device (NSD) for the seismic protection of the base isolated benchmark building in near fault earthquake. The benchmark structure has eight stories and irregular plan, and the superstructure is considered to be a linear elastic system with lateral torsional behavior. Furthermore, it is equipped with low damping elastomeric rubber bearings and viscous dampers for seismic protection. The proposed NSD can change the stiffness of composite structure-device assembly, emulate “apparent yielding” of the structure system without permanent deformations. It consists of a highly compressed spring, a wheel and a curved template that the wheel can roll on. The device can achieve any force-displacement behavior within its designed range. Experimental results are presented to verify the analytical model of the NSD. Numerical simulation results under seven earthquake inputs show that the proposed device is effective in reducing the response of the base and superstructure in comparison with a sample clipped optimal controller and an H2/LQG sample controller.
      PubDate: 2017-03-30T03:45:48.340498-05:
      DOI: 10.1002/stc.1968
  • Tuned liquid column damper for suppressing pitching motion of a floating
           rectangular box structure
    • Authors: Shih-Hsun Yin
      Abstract: This paper aims to investigate the possibility and effectiveness of applying a tuned liquid column damper (TLCD) to suppress pitching motion of a floating box structure. A mathematical model of the TLCD-floating structure interaction system is developed, and the associated equations of motion are derived using a Lagrangian approach. Then, the procedures for numerically obtaining the optimum parameters of the TLCD for the undamped system under harmonic excitation are proposed using Den Hartog's method. The presented examples demonstrate that the TLCD can efficiently suppress the pitching motion of the floating box structure and has potential for applying to the development of floating housing.
      PubDate: 2017-03-30T03:40:34.14903-05:0
      DOI: 10.1002/stc.2014
  • An output-only damage identification method based on H∞ theory and state
           projection estimation error (SP2E)
    • Authors: Armin Lenzen; Max Vollmering
      Abstract: In this article, a new advantageous approach for damage identification of mechanical structures based on state projection estimation error (SP2E) is proposed. The theoretical foundation relies on output-only identification, H∞ theory, estimation error, and state projections. Finally, the proposed damage identification approach is verified by discussing results of laboratory experiments. Therein, structural changes have been applied at a mechanical structure, and the capability to localize them by SP2E has been studied subsequently. By analyzing several different structural alteration positions and extents, an experimental sensitivity study has been conducted, which confirmed the applicability of SP2E for damage localization.
      PubDate: 2017-03-27T01:51:12.870463-05:
      DOI: 10.1002/stc.2003
  • 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
  • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
  • Acceleration-based fault-tolerant control design of offshore fixed wind
    • Authors: C. Tutivén; Y. Vidal, J. Rodellar, L. Acho
      Abstract: Wind turbines (WTs) are basically controlled by varying the generator load torque (with the so-called torque control) and the blade pitch angles (with the so-called pitch control) based on measurement of the generator shaft speed. These two controllers unitedly work to satisfy the control objectives, and it is crucial that they are tolerant to possible faults in the WT system. Passive fault-tolerant control comprises the design of robust controllers against disturbances and uncertainties. This enables the controller to counteract the effect of a fault without requiring reconfiguration or fault detection. In this regard, the main contribution of this paper is to propose new control techniques that not only provide fault tolerance capabilities to the WT system but also improve the overall performance of the system in both fault-free and faulty conditions. Coupling nonlinear aero-hydro-servo-elastic simulations of an offshore WT with jacket platform is carried out for several pitch actuator faults. The jacket platform motions and structural loads caused by fault events with the proposed controllers are compared with loads encountered during normal operation and with respect to a well-known baseline controller in the literature. The proposed controllers are based in the super-twisting algorithm by using feedback of the generator shaft speed as well as the fore-aft and side-to-side acceleration signals of the WT tower. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-02T01:57:27.07033-05:0
      DOI: 10.1002/stc.1920
  • Delamination detection in composite plates by synthesizing time-reversed
           Lamb waves and a modified damage imaging algorithm based on RAPID
    • Authors: Zenghua Liu; Xuwen Zhong, Tuocan Dong, Cunfu He, Bin Wu
      Abstract: Combined with the modified damage imaging algorithm based on Reconstruction Algorithm for the Probabilistic Inspection of Damage (RAPID), a baseline-free detection method of the Lamb waves based on time reversal method is developed to detect the delamination in the composite plate. Through the analysis of the focus position of time reversal signal, a new calculation method of Damage Index (DI) values is proposed. The modified damage imaging algorithm based on RAPID is integrated with two image fusion methods: full summation method and full multiplication method. According to the analysis of limitations of the modified damage imaging algorithm, the transducer array is adopted, and the problem of the uneven probability distribution caused by the uneven density of sensing network is discussed. Modified methods are proposed to eliminate the influence of the uneven probability distribution and improve the accuracy and reliability of the detection results. The parameter β significantly affects the effective detection range of each sensing path in the modified damage imaging algorithm. The value of parameter β was experimentally determined and reasonably applied to detect the delamination. Based on the calculation of the DI of individual sensing path and the imaging results of delamination, the identification and localization of delamination were experimentally achieved. The imaging results demonstrated the problem of the uneven probability distribution and the validity of modified methods. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-02T00:41:01.918994-05:
      DOI: 10.1002/stc.1919
  • Damage localization in a cable-stayed bridge via bio-inspired
           metaheuristic tools
    • Authors: Sara Casciati; Lorenzo Elia
      Abstract: Structural health monitoring is conceived to detect abnormal behaviors in structural systems. A highly non-linear objective function built on the discrepancies between true and generated modal features can be minimized for this purpose. After a finite element discretization is built, the design variables are chosen, and the optimization problem solved. Two bio-inspired metaheuristic tools, namely the artificial bee colony and the firefly algorithm, are employed to proceed toward the global minima. Comparing both identified and analytical stiffness matrices, the damage localization is performed. These methods are tested on a cable-stayed bridge placed in northern Italy. The efficiency of these tools is compared. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-02T00:36:39.772215-05:
      DOI: 10.1002/stc.1922
  • Rolling bearing fault diagnosis under fluctuant conditions based on
           compressed sensing
    • Authors: Hang Yuan; Chen Lu
      Abstract: Bearings are widely used in industries and construction for shaft supporting or seismic isolation. In recent years, their fault diagnosis, especially under variable, or fluctuant conditions, has received increasing attention. Sufficient monitoring data are usually required for bearing diagnosis. However, sufficient data cannot be guaranteed in some engineering cases with limitations of the transmission channel bandwidth or onboard/onsite computational capabilities. Fortunately, the emerging compressed sensing technique, which provides an effective solution to data compression and processing, has the ability to transform traditional monitoring data to the compressed information domain for a highly effective diagnosis under fluctuant conditions. This study proposes a bearing fault diagnosis method under fluctuant conditions based on compressed sensing theory. First, a random matrix is constructed as the measurement matrix and is employed to compress the original signal into the compressed information domain. Then, reconstruction-evaluation based fault diagnosis method is conducted with compressed signals. Moreover, the compressed signals used for fault diagnosis are reconstructed on the remote side. The experimental results provide evidence that the proposed method can effectively reduce the data volume required for bearing diagnosis and maintain an accuracy similar to current approaches, and the reconstructed signals can be used for other fault diagnosis methods. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-08-01T01:30:57.487242-05:
      DOI: 10.1002/stc.1918
  • Shake table investigation of a structure isolated by recycled rubber
           devices and magnetorheological dampers
    • Authors: Giuseppe Maddaloni; Nicola Caterino, Antonio Occhiuzzi
      Abstract: This paper describes the main results obtained from shaking table tests performed on a 1-storey steel frame isolated by innovative rubber bearings and magnetorheological dampers (hybrid isolation). The proposed base isolation technology is based on the use of bearings made of a low-cost recycled elastomer and reinforced with fibre sheets. Bounding the strain demand for such isolators because of severe earthquakes within acceptable values is a key point of this research, crucial for the effective application of this low-cost technology to real cases. A specific semi-active controller has been designed and adopted to achieve this goal. A set of natural earthquake records is applied to the base of the said structure using a shaking table system. The experimental results in terms of base displacement, roof acceleration and interstory drift are compared with the response of the same structure base isolated in the absence of magnetorheological dampers. It is found that when the semi-active control is suitably designed and implemented, the seismic performance of the structure can be significantly improved. Even if referred to the case study, the conclusions encourage further investigating the application of the proposed low-cost technology for seismic protection of buildings. © 2016 The
      Authors . Structural Control and Health Monitoring Published by John Wiley & Sons, Ltd.
      PubDate: 2016-07-26T23:55:35.761098-05:
      DOI: 10.1002/stc.1906
  • Relative vibration attenuation by means of self-active devices constituted
           by permanent magnets separated by silicone layers
    • Authors: Enrico Ricciardi; Giovanni Ausanio, Vincenzo Iannotti, Vittorio Pasquino, Brigida Silvestri, Luciano Lanotte
      Abstract: The relative vibrations of two small frames with different stiffness, subjected to the same oscillating excitation coming from their base platform, were investigated. The effects of the innovative coupling of standard passive attenuation and time variation of magnetic forces (self-produced by the vibration itself) were investigated. The first experimental tests demonstrate that the amplitude of relative vibration can be easily decreased up to 75% without requiring external energy. In perspective, by varying the attenuator shape and power, it is possible to use it in all the cases in which it is necessary to reduce the vibrations of a breakable or unstable structure inside a building accidentally exposed to vibration, such as a rotor inside a frame or a shelf in a museum room. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-26T03:50:37.736917-05:
      DOI: 10.1002/stc.1914
  • Guided wave propagation in H-beam and probability-based damage
    • Authors: Fucai Li; Hongguang Li, Jianxi Qiu, Guang Meng
      Abstract: H-beams are usually made of structural steel and are widely used in construction, civil, and mechanical engineering. Both the rolling process and complex working condition can yield some defects on the H-beam structures. Characteristics of guided wave propagation in H-beam are investigated in this study for damage identification by using guided wave-based structural health monitoring (SHM) technique. Wave structures are obtained for wave mode selection in H-beam SHM applications. Guided waves are excited by using piezoelectric actuators. Two excitation ways, that is, symmetric excitation and circle excitation, are studied to select appropriate wave mode for damage identification. Based on the wave propagation characteristics, probability-based diagnostic image method is proposed to estimate locations of simulated defects. In the image reconstruction process, arithmetic average-based and geometric average-based methods are investigated for damage localization with high precision. The results demonstrate that guided wave-based SHM technique is applicable to damage identification for H-beam structures. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-26T03:50:34.270892-05:
      DOI: 10.1002/stc.1916
  • Hybrid shake table testing method: Theory, implementation and application
           to midlevel isolation
    • Authors: Andreas H. Schellenberg; Tracy C. Becker, Stephen A. Mahin
      Abstract: A 2 m by 6 m unidirectional shake table was constructed at the University of California, Berkeley and combined with a real-time hybrid simulation system creating a hybrid shake table. A series of tests were carried out to examine the viability of real-time hybrid simulation techniques to perform experimental simulations of buildings with midlevel seismic isolation. The isolation system and superstructure were physically tested on the table while the portion of the building below the isolation plane was numerically modeled. OpenFresco was used to interface the numerical model with the control system. The isolated superstructure consisted of a two-story steel moment frame on six triple friction pendulum bearings, which exhibit significant nonlinear velocity-dependent behavior, necessitating real-time testing. Shear building models with a range of periods were used to represent the portion of the building below the isolation plane. Increasing the number of degrees of freedom increased the control difficulty as higher modes were excited in the numerical model because of experimental errors caused predominantly by feedback noise and table tracking. Nonetheless, the results illustrate that hybrid shake table tests are indeed an economical and reasonably accurate method to assess the seismic behavior of midlevel isolation systems installed in a range of building configurations. Results showed that midlevel isolation was beneficial for the superstructure and, to a smaller extent, the substructure. However, to achieve maximum benefits, it is recommended that the effective period of the isolation system be sufficiently longer than the period of the substructure. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-22T04:10:49.221926-05:
      DOI: 10.1002/stc.1915
  • A new filter-based pseudo-negative-stiffness control for base-isolated
    • Authors: Wei Gong; Shishu Xiong
      Abstract: A filter-based pseudo-negative-stiffness (FPNS) control is proposed for seismic control of base-isolated structures. The control algorithm is designed to produce a negative stiffness friction damping force with a gradual change at velocity switches, so that it is potential to prevent structures from experiencing significant jerks especially under earthquakes rich of high-frequency components. The control algorithm requires information only on device's displacement. The effect of the control parameters on structural performance is studied and the optimal combination of control parameters is obtained with the consideration of control efficiency and the economy of control force. The superior performance of an active control system employing the FPNS control algorithm over that employing the conventional PNS control algorithm is verified. A semi-active control design, MC-FPNS, is developed to produce the control force of the FPNS control algorithm by MR dampers. The effectiveness and robustness of the MC-FPNS control system are investigated through numerical analysis of the base-isolated benchmark problem under earthquakes scaled to different intensity levels. The proposed MC-FPNS control system is shown to be effective to not only prevent the isolator from failure but also improve the isolation functionality for a variety of earthquakes with different frequency contents and intensity levels. Moreover, the MC-FPNS control system is capable of suppressing transference of high-frequency components of ground motions to the superstructure. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-19T22:00:39.627815-05:
      DOI: 10.1002/stc.1912
  • Nonlinear imaging of damage in composite structures using sparse
           ultrasonic sensor arrays
    • Authors: F. Ciampa; Simon G. Pickering, Gennaro Scarselli, M. Meo
      Abstract: In different engineering fields, there is a strong demand for diagnostic methods able to provide detailed information on material defects. Low velocity impact damage can considerably degrade the integrity of structural components and, if not detected, can result in catastrophic failures. This paper presents a nonlinear structural health monitoring imaging method, based on nonlinear elastic wave spectroscopy, for the detection and localisation of nonlinear signatures on a damaged composite structure. The proposed technique relies on the bispectral analysis of ultrasonic waveforms originated by a harmonic excitation and it allows for the evaluation of second order material nonlinearities due to the presence of cracks and delaminations. This nonlinear imaging technique was combined with a radial basis function approach in order to achieve an effective visualisation of the damage over the panel using only a limited number of acquisition points. The robustness of bispectral analysis was experimentally demonstrated on a damaged carbon fibre reinforced plastic (CFRP) composite panel, and the nonlinear source's location was obtained with a high level of accuracy. Unlike other ultrasonic imaging methods for damage detection, this methodology does not require any baseline with the undamaged structure for the evaluation of the defect, nor a priori knowledge of the mechanical properties of the specimen. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-19T21:50:33.229032-05:
      DOI: 10.1002/stc.1911
  • Impact load identification for composite structures using Bayesian
           regularization and unscented Kalman filter
    • Authors: Gang Yan; Hao Sun, Oral Büyüköztürk
      Abstract: In structural health monitoring of composite structures, one important task is to detect and identify the low-velocity impact events, which may cause invisible internal damages. This paper presents a novel approach for simultaneously identifying the impact location and reconstructing the impact force time history acting on a composite structure using dynamic measurements recorded by a sensor network. The proposed approach consists of two parts: (1) an inner loop to reconstruct the impact force time history and (2) an outer loop to search for the impact location. In the inner loop, a newly developed inverse analysis method with Bayesian inference regularization is employed to solve the ill-posed impact force reconstruction problem using a state-space model. In the outer loop, a nonlinear unscented Kalman filter (UKF) method is used to recursively estimate the impact location by minimizing the error between the measurements and the predicted responses. The newly proposed impact load identification approach is illustrated by numerical examples performed on a composite plate. Results have demonstrated the effectiveness and applicability of the proposed approach to impact load identification. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-19T03:35:44.82534-05:0
      DOI: 10.1002/stc.1910
  • Semi-active control of flexible structures using closed-loop input shaping
    • Authors: Tarek Edrees Alqado; George Nikolakopoulos, Leonidas Dritsas
      Abstract: In this research effort, a novel approach on the control of structures with magnetorheological (MR) dampers is presented, based on an appropriately adapted closed-loop version of the generic input shaping control theory. The MR damper is a very promising kind of semi-active control system (actuator), mixing the advantages of the active and passive structural control systems, hence their increasing use as attenuators that reject the effects of dynamic loads on civil engineering structures. The main contribution of this article is the application and performance evaluation of the novel ‘Linear Matrix Inequality-based’ feedback version of the input shaping control theory for the first time in the area of structural control. The need for the use of a feedback version of input shaping control stems from the design trade-off between robustness and speed of response requirements. A simulation of a benchmark three-story building with one MR damper is employed to verify the efficiency of the proposed control approach. The nonlinear behaviour of the MR damper, rigidly connected between the first floor of the structure and the ground, is captured by the well-known Bouc–Wen model. The superiority and effectiveness of the proposed scheme in reducing the responses of the structure were proved using seven quantifiable evaluation criteria and by comparing these results with those achieved by classical and well-established alternative control schemes. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-11T02:58:18.261795-05:
      DOI: 10.1002/stc.1913
  • Polygonal damage shape reconstruction in plates using guided Lamb wave
    • Authors: Amir Ashkan Mokhtari; Abdolreza Ohadi, Hamidreza Amindavar
      Abstract: Tomographic reconstruction of the damaged region using guided Lamb waves provides important information about the health condition of structures. Two general types of shape reconstruction techniques are discussed before: transform based methods and algebraic iterative methods. There are some limitations associated with each method such as high sensitivity to noise and incomplete data sets, limitations for damage size and contrast, bulky setup for scanning the damaged region, or low speed of reconstruction. In this paper, the concepts of a novel method for reconstructing the contour of damage based on the Polygon Reconstruction Technique are introduced. First, the projections (Radon transform) of the damaged region are generated from a small number of angles with the aid of beamforming method. Then, the damaged region is modeled by a polygon, which its optimal number of vertices is estimated using the minimum description length (MDL) principle. Finally, using the polygon reconstruction technique, the coordinates of the vertices are determined. As the proposed method is at its preliminary stage, two finite element models of an aluminum plate with two different holes as the damage are designed in ABAQUS to examine the feasibility and performance of the method. Results show that the introduced technique based on polygonal damage shape reconstruction is fast and accurate. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-07-06T23:55:40.944939-05:
      DOI: 10.1002/stc.1907
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