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    - ENERGY (180 journals)
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ENERGY (180 journals)                  1 2 | Last

Advances in Building Energy Research     Hybrid Journal   (Followers: 14)
Advances in Energy and Power     Open Access   (Followers: 4)
Advances in High Energy Physics     Open Access   (Followers: 14)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 17)
AIMS Energy     Open Access  
American Journal of Energy Research     Open Access   (Followers: 8)
Annals of Nuclear Energy     Hybrid Journal   (Followers: 8)
Annual Reports on NMR Spectroscopy     Full-text available via subscription   (Followers: 1)
Annual Review of Resource Economics     Full-text available via subscription   (Followers: 11)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Solar Energy     Hybrid Journal   (Followers: 13)
Archives of Thermodynamics     Open Access   (Followers: 6)
Artificial Photosynthesis     Open Access  
Atomic Energy     Hybrid Journal   (Followers: 5)
Atoms for Peace: an International Journal     Hybrid Journal   (Followers: 3)
Batteries     Open Access   (Followers: 1)
Biofuel Research Journal     Open Access   (Followers: 3)
Biofuels     Hybrid Journal   (Followers: 11)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 7)
Bulletin de droit nucleaire     Full-text available via subscription   (Followers: 1)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 13)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbon Management     Hybrid Journal   (Followers: 8)
Catalysis for Sustainable Energy     Open Access   (Followers: 4)
CERN courier. International journal of high energy physics     Free   (Followers: 2)
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: 3)
Dams and Reservoirs     Hybrid Journal   (Followers: 4)
Development of Energy Science     Open Access   (Followers: 5)
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: 5)
Electrical and Power Engineering Frontier     Open Access   (Followers: 11)
Energy     Partially Free   (Followers: 27)
Energy & Fuels     Full-text available via subscription   (Followers: 26)
Energy and Buildings     Hybrid Journal   (Followers: 10)
Energy and Emission Control Technologies     Open Access   (Followers: 2)
Energy and Environment Focus     Free   (Followers: 1)
Energy and Environment Research     Open Access   (Followers: 12)
Energy and Environmental Engineering     Open Access   (Followers: 2)
Energy and Power     Open Access   (Followers: 4)
Energy and Power Engineering     Open Access   (Followers: 11)
Energy Conversion and Management     Hybrid Journal   (Followers: 11)
Energy Efficiency     Hybrid Journal   (Followers: 14)
Energy Harvesting and Systems : Materials, Mechanisms, Circuits and Storage     Hybrid Journal   (Followers: 3)
Energy Journal The     Full-text available via subscription   (Followers: 2)
Energy Law Journal     Full-text available via subscription   (Followers: 3)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 17)
Energy Policy     Partially Free   (Followers: 49)
Energy Prices and Taxes     Full-text available via subscription   (Followers: 6)
Energy Procedia     Open Access   (Followers: 4)
Energy Reports     Open Access   (Followers: 2)
Energy Research & Social Science     Full-text available via subscription   (Followers: 2)
Energy Science & Engineering     Open Access   (Followers: 5)
Energy Science and Technology     Open Access   (Followers: 13)
Energy Strategy Reviews     Partially Free   (Followers: 8)
Energy Studies Review     Open Access   (Followers: 5)
Energy Systems     Hybrid Journal   (Followers: 12)
Energy Technology     Partially Free   (Followers: 4)
Energy Technology & Policy     Open Access   (Followers: 1)
Energy, Sustainability and Society     Open Access   (Followers: 19)
Environmental Progress & Sustainable Energy     Hybrid Journal   (Followers: 6)
EPJ Photovoltaics     Open Access   (Followers: 2)
Facta Universitatis, Series : Electronics and Energetics     Open Access  
Frontiers in Energy     Hybrid Journal   (Followers: 4)
Frontiers in Energy Research     Open Access   (Followers: 2)
Fuel and Energy Abstracts     Full-text available via subscription   (Followers: 5)
Functional Materials Letters     Hybrid Journal   (Followers: 1)
Gcb Bioenergy     Hybrid Journal   (Followers: 2)
Geothermal Energy     Open Access   (Followers: 1)
GeoWorld     Full-text available via subscription   (Followers: 2)
Green     Hybrid Journal   (Followers: 2)
IEA Electricity Information     Full-text available via subscription   (Followers: 6)
IEA Natural Gas Information     Full-text available via subscription   (Followers: 4)
IEEE Power and Energy     Full-text available via subscription   (Followers: 12)
IEEE Transactions on Energy Conversion     Hybrid Journal   (Followers: 7)
IEEE Transactions on Nuclear Science     Hybrid Journal   (Followers: 7)
IEEE Transactions on Power Systems     Hybrid Journal   (Followers: 12)
IET Power Electronics     Hybrid Journal   (Followers: 14)
IngenierĂ­a EnergĂ©tica     Open Access  
Innovations : Technology, Governance, Globalization     Hybrid Journal   (Followers: 6)
International Journal of Alternative Propulsion     Hybrid Journal   (Followers: 1)
International Journal of Ambient Energy     Hybrid Journal   (Followers: 1)
International Journal of Applied Power Engineering     Open Access   (Followers: 2)
International Journal of Clean Coal and Energy     Open Access   (Followers: 6)
International Journal of Coal Science & Technology     Open Access   (Followers: 2)
International Journal of Critical Infrastructure Protection     Hybrid Journal   (Followers: 6)
International Journal of Electric and Hybrid Vehicles     Hybrid Journal   (Followers: 7)
International Journal of Emerging Electric Power Systems     Hybrid Journal   (Followers: 5)
International Journal of Emerging Multidisciplinary Fluid Sciences     Full-text available via subscription  
International Journal of Energy and Environmental Engineering     Open Access   (Followers: 2)
International Journal of Energy and Power     Open Access   (Followers: 7)
International Journal of Energy and Statistics     Hybrid Journal  
International Journal of Energy Engineering     Open Access   (Followers: 11)
International Journal of Energy Research     Hybrid Journal   (Followers: 10)
International Journal of Energy Science     Open Access   (Followers: 1)
International Journal of Flow Control     Full-text available via subscription   (Followers: 4)
International Journal of Global Energy Issues     Hybrid Journal   (Followers: 7)
International Journal of Green Energy     Hybrid Journal   (Followers: 7)

        1 2 | Last

Journal Cover   Structural Control and Health Monitoring
  [SJR: 1.351]   [H-I: 26]   [5 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1545-2255 - ISSN (Online) 1545-2263
   Published by John Wiley and Sons Homepage  [1597 journals]
  • Full‐scale bridge damage identification using time series analysis
           of a dense array of geophones excited by drop weight
    • Authors: Reza V. Farahani; Dayakar Penumadu
      Abstract: This paper presents a simple and inexpensive technique for damage identification of bridges using drop weight vibration data of bridges recorded by an array of geophones, highly sensitive sensors to record vibration, and time series analysis. The dynamic response of bridges obtained using drop weight as an excitation source is convolved with white noise to create suitable input for autoregressive (AR) models. A two‐stage prediction model, combined AR and autoregressive with exogenous input (ARX), is employed to obtain a damage‐sensitive feature. An outlier analysis method is developed based on the Monte Carlo simulation to identify the existence of damage. The proposed technique is verified using unique vibration data of two full‐scale steel‐girder bridges located on I‐40 through downtown Knoxville, Tennessee, and subjected to progressive damage scenarios induced to steel girders. The results of the analysis for the vertical vibration data of the test bridges indicate that the proposed technique is able to detect the damage induced on the real bridge girders consistently even when the damage level is small and damage is located near a support; however, damage is not well localized or quantified in these two highly redundant bridges. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-25T03:21:41.951305-05:
      DOI: 10.1002/stc.1820
  • Modeling and experimental validation of a
           multiple‐mass‐particle impact damper for controlling
           stay‐cable oscillations
    • Authors: Philipp Egger; Luca Caracoglia, Johann Kollegger
      Abstract: Impact dampers are often used in the field of civil, mechanical, and aerospace engineering for reducing structural vibrations. This research is motivated by a practical problem, that is, the reduction of wind‐induced and rain–wind‐induced vibrations in long, flexible and low‐damping stay‐cables. A new concept of distributed‐mass impact damper has been proposed, designed, fabricated, and tested experimentally at Vienna University of Technology by using a 31.2‐m actual stay. The results of the full‐scale experiments (free‐decay tests) are illustrated in this study. Because the performance of the new device was very promising, with total damping ratio three to 10 times larger than the original damping in the stay, modeling of the damper device was needed to ensure adequate practical application in the future. This study examines three different reduced‐order models, derived in an attempt to characterize the complex behavior of the new device. Verification and validation of the models are carried out by comparison with the experimental results. Finally, selection of an adequate model, based on both experiments and simulations, is described and discussed. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-12T20:39:32.554385-05:
      DOI: 10.1002/stc.1812
  • Multiple‐crack identification in a channel section steel beam using
           a combined response surface methodology and genetic algorithm
    • Authors: Palash Dey; S. Talukdar, D. J. Bordoloi
      Abstract: The present study outlines a sequentially integrated finite‐element method (FEM)–response surface method (RSM)–genetic algorithm (GA) framework and implements this to predict the crack parameters, namely, crack location and crack depth ratio. A central composite face centered response surface design of the RSM technique is used to establish the direct relationships between the input parameters (crack location and crack depth ratio) and responses (natural frequencies) to build the response surface function (RSF). Multiple edge cracks are considered, which exist on the top flange of a thin‐walled channel section cantilever beam and modeled as line spring elements. In order to obtain RSFs of the first five natural frequencies in terms of process factors such as crack position and crack depth ratio, a number of numerical experiments based on FEM are conducted by using the design‐of‐experiment approach. An objective function obtained as the square of the difference between RSF and experimentally measured natural frequency has been minimized using GA to find out the optimum crack parameters. Twenty‐four steel channel beam specimens have been tested in the laboratory to extract the crack parameters from measured natural frequencies using the proposed approach. The results of the study indicate that the proposed approach performs remarkably, yielding crack parameters with great precision. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-10T22:11:47.025626-05:
      DOI: 10.1002/stc.1818
  • Automatic mapping of moisture affectation in exposed concrete structures
           by fusing different wavelength remote sensors
    • Abstract: Water content is a critical parameter for the early detection of moisture degradation in exposed concrete structures. Traditionally, visual inspection is the most extended procedure to detect superficial pathologies caused by moisture in concrete constructions, principally when access is limited. For such cases, remote sensing is a valuable tool to recover radiometric information useful for detecting and quantifying different degrees of affectation caused by water. This paper presents an approach to identifying and evaluating the water content in a real concrete structure by fusing several sensors recording data in different wavelengths. In particular, a procedure to integrate three‐dimensional intensity data collected by two terrestrial laser scanners (Riegl‐Z390i and FARO Focus 3D) with two‐dimensional radiometric data provided by a six‐band multispectral camera and a commercial digital camera (MCA6 Tetracam and Canon EOS 5D) is developed. After data fusion in a two‐dimensional space, a multiband image was created for further spectral analysis. Finally, an unsupervised classification using clustering algorithms was performed to identify the degrees of affectation and the most suitable remote sensor for moisture mapping. Comparisons between the sensors used in this survey reveal that intensity imagery from both laser scanners has high potential for the recognition and characterisation of the degree of moisture in this type of structure. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-08T23:02:05.198576-05:
      DOI: 10.1002/stc.1814
  • Novel hexapod‐based unidirectional testing and FEM analysis of the
           RNC isolator
    • Authors: Mohammed Ismail
      Abstract: An innovative Stewart platform (hexapod)‐based testing rig is designed, constructed, and used herein to experimentally characterize a seismic isolation device named roll‐in‐cage (RNC) isolator. The testing rig is a result of integrating a mechanical extension, or upgrade, to the hexapod. This allows for performing up to 15 standard mechanical tests using cylinder, block, prism, beam, plate, or bar specimens, besides reduced‐scale prototypes of seismic isolation bearings. Several one‐tenth reduced‐scale prototypes of the RNC isolator are experimentally examined in this paper using this testing rig. Cyclic horizontal displacement tests are performed considering different test parameters including shear displacement amplitude, axial load, and loading frequency. The RNC isolator's force–displacement relationships, shear stiffness, and damping properties are investigated. Vertical cyclic displacements are also applied to examine the RNC isolator's capability to withstand vertical axial tension. Furthermore, tests at the ultimate level consisting of an increasing‐amplitude shear loading, beyond the bearing's design displacement limit, are also carried out to investigate the bearing's behavior after activating its inherent self‐stopping, or buffer, mechanism. The obtained experimental outputs are then related to analytical and thorough FEM simulation outputs. This relation is intended to validate those previously developed mathematical and numerical models of the RNC isolator based on the real experimental measurements in this paper. A comparative study of the results is then performed, and the main observations are highlighted. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-05T01:03:05.176122-05:
      DOI: 10.1002/stc.1817
  • Vision‐based multipoint displacement measurement for structural
           health monitoring
    • Authors: Dongming Feng; Maria Q. Feng
      Abstract: A novel noncontact vision sensor for simultaneous measurement of structural displacements at multiple points using one camera is developed based on two advanced template matching techniques: the upsampled cross correlation (UCC) and the orientation code matching (OCM). While existing studies on vision sensors are mostly focused on the time‐domain performance evaluation, this study investigates the performance in both time and frequency domains through a shaking table test of a three‐story frame structure, in which the displacements at all the floors are measured by using one camera to track either high‐contrast artificial targets or low‐contrast natural targets on the structural surface such as bolts and nuts. Excellent agreements are observed between the displacements measured by the single camera and those measured by high‐performance laser displacement sensors. The results of structural modal analysis based on the measurements by the vision sensor and reference accelerometers also agree well. Moreover, the identified modal parameters are used to update the finite element model of the structure, demonstrating the potential of the vision sensor for structural health monitoring applications. This study further examines the robustness of the proposed vision sensor against ill environmental conditions such as dim light, background image disturbance, and partial template occlusion, which is important for future implementation in the field. Significant advantages of the proposed vision sensor include its low cost (a single camera to remotely measure structural displacements at multiple points without installing artificial targets) and flexibility to extract structural displacements at any point from a single measurement. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-05T00:45:34.260543-05:
      DOI: 10.1002/stc.1819
  • Using a phase difference detection technique for monitoring the structural
           health of bridge piers
    • Abstract: In this study, a new technique for monitoring the structural health of bridge piers, from the point of view of earthquake‐induced damage, is introduced and then simulated and evaluated using a scaled model of a typical bridge. This system uses the detection of phase difference between two synchronous receiver nodes, connected through a wireless sensor network, and utilizes an array of inexpensive, high‐frequency oscillator circuits (4 GHz) as wireless transmitters, placing them at the important structural positions of the bridge piers, and then receiving and analyzing the signals sent by these transmitters to the two receiver nodes. The proposed monitoring system measures the changes in phase difference between two synchronous receiver nodes before and after damage (displacement or deformation); it shows an accuracy of a tenth of a millimeter in the simulations, and it also has high reliability in monitoring the structural heath of the bridge because it provides a real‐time report of the status of each transmitter (activated, deactivated, and damaged). The proposed system is low in price compared to other structural health monitoring (SHM) methods and also entails a much lower volume and complexity of data processing than similar techniques. This study did not carry out any field trials, but a complete simulation using an array of six transmitters (TX) and two receivers (RX) was conducted for a scaled model with six piers, and mathematical and geometrical principles and signal processing and simulation details were thoroughly examined. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-05T00:26:16.908969-05:
      DOI: 10.1002/stc.1813
  • Issue Information
    • Abstract: No abstract is available for this article.
      PubDate: 2015-11-03T04:35:20.970732-05:
      DOI: 10.1002/stc.1701
  • Field dynamic test and Bayesian modal identification of a special
           structure – the Palms Together Dagoba
    • Abstract: The Palms Together Dagoba at Famen Temple is a 12‐story steel‐reinforced concrete building, which comprises a vertical inversion and setback tubes with two inflection points formed along its height. It contains two towers with the first two and the top two floors connected, while the remaining floors are separated forming an irregular configuration. During its construction, an earthquake of 8.0 magnitude struck about 500 km away. The seismic intensity at the site is reported to be 6, which may result in some cracks for the local structures. This paper presents the work on field test 1 month after the earthquake and modal identification of the Dagoba. To determine the dynamic characteristics of this structure, ambient vibration tests were performed. Four setups were designed to cover all the degrees of freedom of interest involving the floors from the ground to the roof. A recently developed Bayesian method incorporating multi‐setups was employed to identify the modal properties by using the data in all the setups simultaneously. In addition to the most probable values, the associated posterior uncertainties were also obtained, providing an estimation tool to assess the accuracy of the modal parameters. These results were utilized to investigate the modal properties of this structure. The influence due to the earthquake was also studied based on the observation in the field. Before the full‐scale field tests, shaking table tests were also implemented. The dynamic properties from the two different tests, as well as their posterior uncertainties, were compared and discussed in the paper. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-03T02:41:06.979489-05:
      DOI: 10.1002/stc.1816
  • Impact energy level assessment of composite structures using
           MUSIC‐ANN approach
    • Authors: Yongteng Zhong; Jiawei Xiang, Haifeng Gao, Yuqing Zhou
      Abstract: Impact damage effects on the residual mechanical properties of the structure can be quite detrimental, and failure patterns depend strongly on the impact energy levels. This paper presents impact energy level assessment method using 2D multiple signal classification (MUSIC) and artificial neural network (ANN) approach for composite structures. Because uniform linear array has the shortcoming of the half‐plane mirror effect, 2D MUSIC algorithm using a plum blossom sensor array is firstly applied to locate the position of impact and extract impact energy feature. Secondly, the relation impact energy feature, impact position, and impact energy level at different measurement points are established using ANN approach. Through the trained ANN, the impact energy level can be predicted when the position and impact energy feature results of unknown impact are given as input. Finally, the proposed method is applied to a quasi‐isotropic epoxy laminate plate and a large stiffened carbon fiber composite structure showing its successful performance on composite structure. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-03T02:26:41.036773-05:
      DOI: 10.1002/stc.1815
  • Proof of concept of the structural health monitoring of framed structures
           by a novel combined experimental and theoretical approach
    • Authors: D. Isidori; E. Concettoni, C. Cristalli, L. Soria, S. Lenci
      Abstract: One of the most important issues in engineering is the detection of structural damages. During its life cycle, a building, besides the exposure to operational and environmental forces, can be subjected to earthquakes or to other non‐ordinary loads. These events may have a deep impact on the building safety, and thus, a continuous monitoring of the structure health conditions becomes desirable or even necessary in many cases. In this context, the usage of vibration‐based structural health monitoring (SHM) systems is spreading from big infrastructures applications, like bridges, dams or skyscrapers, to the historical heritage and to public or residential buildings. The aim of this work is to propose a combined experimental and numerical methodology to perform the SHM of structures of the civil engineering lying in seismic hazard zones. A relatively low cost SHM prototype system based on this approach is developed. The data acquired by the system are provided to a finite element method (FEM) numerical model to detect the appearing, the rise and the distribution of local damages and to estimate a global damage level. The system has been tested and calibrated on a three‐storey prototype model. The procedure for the estimation of the damage level is calibrated by comparing the experimental quantities measured during cyclic failure tests with the FEM model predictions. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-02T05:55:39.331486-05:
      DOI: 10.1002/stc.1811
  • Linear dynamic analysis and active control of space prestressed taut cable
           net structures using wave scattering method
    • Authors: Zuowei Wang; Tuanjie Li
      Abstract: In this paper, the linear dynamic analysis and active control of prestressed taut cable net structures are investigated by the wave scattering method. Wave motion equations of cables are firstly derived to obtain the wave dispersion characteristics, which are the combinations of the longitudinal tensile wave equations of bars and transverse wave equations of taut strings. The waveguide and scattering matrices of cables are then formed by the force balance and displacement boundary conditions. The derivation of the traveling wave model of cable net structures is accomplished by combining systematic scattering matrix with transmission matrix. Finally, the wave active control method is proposed based on the established traveling wave model. The comparison of results obtained by the wave scattering method with the finite element method shows an excellent agreement. But more importantly, it demonstrates that the computational efficiency of the wave scattering method is higher for dynamic analysis of large‐scale cable net structures. The effectiveness of the proposed wave active control method is verified by a planar cable net structure. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-10-22T03:07:49.747522-05:
      DOI: 10.1002/stc.1810
  • Modeling and control performance of a negative stiffness damper for
           suppressing stay cable vibrations
    • Authors: Peng Zhou; Hui Li
      Abstract: A negative stiffness damper (NSD) is proposed, and its performance on suppressing stay cable vibrations is investigated by numerical simulations and experimental tests. First, the NSD consists of two pressed springs and an oil damper. The two pressed springs are attached perpendicularly to the piston rod of the oil damper in symmetrical configuration. Mechanical model of this damper is derived according to the geometrical configuration and validated experimentally. Considering the simplified model of single‐mode vibration of a cable, the cable frequency with the NSD is investigated theoretically by average method, and the lower limit on the pressed degree of two springs is proposed. Numerical examples of cable with NSD and oil damper under sinusoidal excitations are conducted. The NSD shows the superior reduction performance of both amplitudes in time history and peak values of frequency response. A series of single‐mode and multi‐mode cable vibration control experiments are carried out to evaluate mitigation performance achieved by the NSD. The results indicate that this NSD can provide larger additional modal damping ratio to the cable regardless of single‐mode and multiple‐mode vibration. Thus, this NSD achieves further reduction of the cable than the oil damper through negative stiffness behavior, instead of complex active or semi‐active devices with real‐time feedback. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-10-12T23:38:49.516717-05:
      DOI: 10.1002/stc.1809
  • Structural monitoring for the cyclic behaviour of concrete tunnel lining
           sections using FBG sensors
    • Authors: Oreste S. Bursi; Nicola Tondini, Manuel Fassin, Alessio Bonelli
      Abstract: To demonstrate the viability of using fibre Bragg grating (FBG) sensors capable of detecting the inelastic cyclic response of reinforced concrete sections that are part of tunnel linings, an experimental research programme carried out on different packaging configurations of FBG sensors is presented in this paper. The programme illustrated here was part of a wider research project funded by the European Commission whose objective was the development of a decision support system for monitoring tunnel linings in seismic‐prone regions. In particular, a typical metro tunnel located in Rome area, Italy, was considered as a case study. In order to provide useful information for designing an effective sensor packaging to be applied to a final full‐scale test representing a whole lining circular section of a tunnel, pure bending tests were designed and performed on five substructure specimens endowed with different sets of fibre packaging. The outcomes of the substructure tests showed that the optimal FBG packaging solutions were unbonded sensors either embedded in concrete or mounted externally. Moreover, the designed fibre sensor system reliably performed at large deformations. In fact, the external FBG fibres applied to the full‐scale tunnel test approached maximum values of about 0.63%, whilst the internal fibres reached about 1.2%. The results obtained by FBG sensors were in good agreement with those of traditional transducers. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-10-12T23:37:03.532476-05:
      DOI: 10.1002/stc.1807
  • Real‐time hybrid testing with equivalent force control method
           incorporating Kalman filter
    • Abstract: The equivalent force control (EFC) method has been developed for real‐time hybrid testing to replace the numerical iteration of implicit integration with a force‐feedback control loop. With this control loop, the EFC method can also compensate for the time delay in real‐time hybrid testing. However, the delay compensation effect of the EFC can be influenced by factors such as noises in the measured displacement. This paper discusses the influence of the measurement noises on real‐time hybrid testing with the EFC. The Kalman filter is proposed to filter the noises in the measured actuator displacement for improved performance. A higher proportional gain in the PID controller, which improves the effect of time delay compensation of the EFC method, can be allowed without losing stability when incorporating the Kalman filter. A series of real‐time hybrid tests were conducted, and the results validated that the EFC method with Kalman filter can effectively compensate for the time delay. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-10-08T23:57:44.958064-05:
      DOI: 10.1002/stc.1808
  • Multiaxial sensor placement optimization in structural health monitoring
           using distributed wolf algorithm
    • Abstract: Optimal sensor placement technique plays a key role in the design of an effective structural health monitoring system. Recent advances in sensing technologies have also promoted using multiaxial sensors to perform efficiently and economically monitoring for civil engineering structures. However, the available evaluation criteria for the optimal sensor placement can only guarantee that the optimization is conducted in a single structural direction but not in multi‐dimension space, which may result in the non‐optimal placement of multiaxial sensors. To tackle this issue thoroughly, a new multiaxial optimal criterion termed as the triaxial modal assurance criterion is developed by taking account into three translational degrees of freedom as a single unit in the Fisher information matrix. Afterwards, a novel distributed wolf algorithm is proposed to improve the optimization performance in identifying the best sensor locations. The dual‐structure coding method is improved and adopted to represent the solution. The shuffling strategy is proposed to enhance the searching capability and convergence performance. The attacking process is also modified to prevent the algorithm from being trapped in a local minimum. The effectiveness of the proposed scheme is investigated by the benchmark structure developed by the University of Central Florida, USA. The results clearly demonstrate that the proposed distributed wolf algorithm outperforms the existing algorithm in its global optimization capability. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-10-01T01:01:40.870475-05:
      DOI: 10.1002/stc.1806
  • Designing the control law on reduced‐order models of large
           structural systems
    • Authors: Fabio Casciati; Sara Casciati
      Abstract: The design of a control law requires two preliminary actions: to introduce a numerical model of the system to be controlled, together with its reduced‐order approximation, and to fix the number and positions of the actuators, together with those of the sensors providing the feedback. The link between measured acceleration quantities and model variables was successfully demanded to the Kalman filter in seismic applications. When moving to wind excitation, the standard approach is no longer viable, and one meets several options, which are discussed in the paper. A timber footbridge is studied to provide a numerical example. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-10-01T00:16:33.421819-05:
      DOI: 10.1002/stc.1805
  • Blind identification of the Millikan Library from earthquake data
           considering soil–structure interaction
    • Abstract: The Robert A. Millikan Library is a reinforced concrete building with a basement level and nine stories above the ground. Located on the campus of California Institute of Technology (Caltech) in Pasadena California, it is among the most densely instrumented buildings in the U.S. From the early dates of its construction, it has been the subject of many investigations, especially regarding soil–structure interaction effects. It is well accepted that the structure is significantly interacting with the surrounding soil, which implies that the true foundation input motions cannot be directly recorded during earthquakes because of inertial effects. Based on this limitation, input–output modal identification methods are not applicable to this soil–structure system. On the other hand, conventional output‐only methods are typically based on the unknown input signals to be stationary whitenoise, which is not the case for earthquake excitations. Through the use of recently developed blind identification (i.e. output‐only) methods, it has become possible to extract such information from only the response signals because of earthquake excitations. In the present study, we employ such a blind identification method to extract the modal properties of the Millikan Library. We present some modes that have not been identified from force vibration tests in several studies to date. Then, to quantify the contribution of soil–structure interaction effects, we first create a detailed Finite Element (FE) model using available information about the superstructure; and subsequently update the soil–foundation system's dynamic stiffnesses at each mode such that the modal properties of the entire soil–structure system agree well with those obtained via output‐only modal identification. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-09-29T22:33:28.538984-05:
      DOI: 10.1002/stc.1803
  • Design and performance tests of a LED‐based two‐dimensional
           wireless crack propagation sensor
    • Authors: S. H. Man; C. C. Chang
      Abstract: In this study, a wireless light‐emitting diode (LED)‐based crack sensor is proposed for monitoring two‐dimensional crack propagation on concrete structures. This sensor is developed by incorporating a LED optical navigation sensor board (ADNS‐2620) into a smart wireless platform (Arduino Pro Mini + XBee). To measure crack propagation, the Arduino Pro Mini sends a signal to the ADNS‐2620 to collect a sequence of images reflected from a grid pattern attached on a concrete surface. The normalized cross‐correlation method is used to compute the two‐dimensional crack propagation using the image sequence. Three different computational approaches were proposed and studied: the moving reference, the absolute reference, and the hybrid reference. The computed crack movements can then be transmitted wirelessly through the XBee modulus to a base station. The design of this sensor is reported herein followed by a series of calibration and performance tests. Results of the performance test on a shake table show that the accuracy of sensor is in the order of 13 µm. A bending test on a concrete beam is further used to illustrate the applicability of the sensor. Results show that the proposed sensor has a potential for monitoring crack propagation of concrete structures. Comparing to a previously developed laser‐based crack sensor, the proposed LED‐based crack sensor offers a better accuracy but with one third less of power consumption. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-09-29T21:46:35.533556-05:
      DOI: 10.1002/stc.1802
  • A study on the structural stability of the Asinelli Tower in Bologna
    • Authors: Alberto Carpinteri; Giuseppe Lacidogna, Amedeo Manuello, Gianni Niccolini
      Abstract: This study concerns the structural stability of the Asinelli Tower in Bologna. This building is the tallest and, with the Garisenda Tower, the most undisputed symbol of the City of Bologna. The stability conditions of the tower were analyzed by means of the Acoustic Emission technique. Specifically, this approach was used to analyze the influence of repetitive and impulsive events of natural or anthropic origin, such as earthquakes, wind, or vehicle traffic on the damage evolution of the tower. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-09-28T00:55:11.551851-05:
      DOI: 10.1002/stc.1804
  • A state space‐based explicit integration method for real‐time
           hybrid simulation
    • Abstract: Real‐time hybrid simulation (RTHS) combines experimental testing with numerical simulation. It provides an alternative method to evaluate the performance of structures subjected to dynamic loading such as earthquake or wind. During RTHS, a numerical integration algorithm is employed to directly solve the equation of motion and generate command displacements for the experimental test structure online. This paper presents an improved explicit numerical integration method for RTHS based on discrete state space formulation. The improved integration method utilizes an extrapolation‐based prediction procedure for command displacement by applying a zero‐order hold. The predicted command displacement is then used to compute the final command displacement by applying a first‐order hold. Both the stability and the accuracy of the proposed integration method are investigated using control theory and numerical and experimental simulations. The proposed method demonstrates improved performance compared with other integration methods. The robustness and feasibility of the proposed method were verified through experimental RTHS on two different computational platforms including a National Instruments system and a dSPACE embedded controller. The proposed method may also be implemented on other platforms containing an xPC target and MATLAB environment. By placing the algorithm on the dSPACE system, any dynamically rated actuator with a controller that can receive analog signal may be used for RTHS. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-09-15T01:26:55.732517-05:
      DOI: 10.1002/stc.1798
  • A bidirectional tuned liquid column damper for reducing the seismic
           response of buildings
    • Abstract: In this article, a new bidirectional tuned liquid column damper (BTLCD) is proposed for controlling the seismic response of structures. The device acts as two independent and orthogonal tuned liquid column dampers (TLCDs), but due to its configuration, it requires less liquid than two equivalent independent TLCDs. The equations of motion of the system formed by the BTLCD and the primary structure to be controlled are obtained by means of Lagrangian dynamics explicitly considering the non‐symetrical action of the damping forces. First, the primary structure was assumed to have two degrees of freedom (DOFs). Assuming that the system is excited by a base acceleration that can be considered to be a white noise random process, the optimum design parameters of the device were obtained to minimise the response of the primary structure. The optimum design parameters are presented as expressions covering a wide range of possible configurations for the device in a controlled structure. The use of a BTLCD to control the seismic response of several DOF structures was also studied, showing that if the structural response occurs mainly in two perpendicular modes, then the optimum design parameters for two DOF structures can be used. Experimental analyses of the BTLCD are developed in order to verify its dynamical properties. Finally, the device is designed for controlling the seismic response of a six DOF scale model. Numerical analyses are developed in order to verify the effectiveness and accuracy of the equations and design procedures proposed herein. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-09-14T01:01:52.426057-05:
      DOI: 10.1002/stc.1784
  • Updating of an instrumented building model considering amplitude
           dependence of dynamic resonant properties extracted from seismic response
    • Authors: Piotr Omenzetter; Faheem Butt
      Abstract: This paper presents system identification and numerical analyses of a three‐story RC building. System identification was performed using 50 earthquake response records to obtain the frequencies and damping ratios, taking into account soil–structure interaction. Trends in the resonant parameters were correlated with the peak response accelerations at the roof level. A general trend of decreasing resonant frequencies with increasing level of response was observed and quantified, whereas for the damping ratios, no clear trends were discernible. A series of finite element models (FEMs) of the building were updated using a sensitivity‐based method with a Bayesian parameter estimation technique to follow the changes in the resonant frequencies with response amplitude. The FEMs were calibrated by tuning the stiffness of structural and non‐structural components and soil. The updated FEMs were used in time history analyses to predict and assess the building seismic performance at the serviceability limit state. It was concluded that the resonant frequencies depend strongly on the response magnitude, even for low‐to‐moderate levels of shaking. The structural and non‐structural components and soil make contributions to the overall building stiffness that depends on the level of shaking. The FEM calibrated to the largest responses was the least conservative in predicting the serviceability limit state inter‐story drifts, but the building performed satisfactorily. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-09-14T00:58:35.385372-05:
      DOI: 10.1002/stc.1801
  • Monitoring leaning towers by geodetic approaches: effects of subsidence
           and earthquake to the Ghirlandina Tower
    • Authors: Cristina Castagnetti; Eleonora Bertacchini, Alessandro Capra
      Abstract: The research focuses on structural monitoring and movements identification applied to cultural heritage protection. The final purpose is the integration among different and independent technologies for analyzing and investigating the geometry changing over time of ancient leaning towers. The paper deals with a novel strategy implemented to compute differential vertical displacements starting from results obtained by repeated high‐precision leveling network adjustments. These results usually aim at monitoring the subsidence phenomenon, while their use in engineering applications is more or less absent in literature. Moreover, the multidisciplinary approach is also able to analyze subsidence gradients in order to extrapolate the trend of the vertical axis and compute structure's rotations. The approach is applied to the Ghirlandina Tower, Modena (Italy), in order to identify the leaning and the subsidence trend. About 30 years of leveling campaigns provide a useful dataset to test the methodology, which is finally validated by the independent observations collected by a pendulum. The approach allows to compute the mean total displacement since 1984 of about 4.7 cm with 30% occurring over the last 6 years. In the same period, the total overhang of the tower (1.30 m in 2007) increased by about 19.1 and 10.4 mm towards southwest. The approach is also able to identify anomalous behavior of the tower such as the reversal tilting trend due to the scaffolding in the years of restoration and the permanent deformation suffered after the 2012 Emilia Romagna earthquake (failure of 4 mm in 6 months). Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-09-10T00:08:31.535017-05:
      DOI: 10.1002/stc.1799
  • Ultrasonic health monitoring in structural engineering: buildings and
    • Abstract: Ultrasonic monitoring is one of the most important tools in the field of structural health monitoring (SHM). The main goal of this paper is to provide a comprehensive review of the recent advances and achievements in ultrasonic wave SHM of buildings and bridges built with concrete and steel materials and the types of sensors used in these structures. In this paper, the parameters affecting the monitoring process, including the type of damage, the type of ultrasonic wave, and the type of sensor, are reviewed. The sensor devices used to transmit and receive ultrasonic waves, like lead zirconate titanate, electromagnetic acoustic transducer, and others and their applications in building and bridges, are discussed. The limitations of each type of theses sensors are highlighted. Finally, conclusions are drawn and recommendations for an improved sensor overcoming the shortcomings of the current sensors are given. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-09-09T04:41:29.0468-05:00
      DOI: 10.1002/stc.1800
  • Comparative studies on damage identification with Tikhonov regularization
           and sparse regularization
    • Authors: C. D. Zhang; Y. L. Xu
      Abstract: Structural damage identification is essentially an inverse problem. Ill‐posedness is a common obstacle encountered in solving such an inverse problem, especially in the context of a sensitivity‐based model updating for damage identification. Tikhonov regularization, also termed as ℓ2‐norm regularization, is a common approach to handle the ill‐posedness problem and yields an acceptable and smooth solution. Tikhonov regularization enjoys a more popular application as its explicit solution, computational efficiency, and convenience for implementation. However, as the ℓ2‐norm term promotes smoothness, the solution is sometimes over smoothed, especially in the case that the sensor number is limited. On the other side, the solution of the inverse problem bears sparse properties because typically, only a small number of components of the structure are damaged in comparison with the whole structure. In this regard, this paper proposes an alternative way, sparse regularization, or specifically ℓ1‐norm regularization, to handle the ill‐posedness problem in response sensitivity‐based damage identification. The motivation and implementation of sparse regularization are firstly introduced, and the differences with Tikhonov regularization are highlighted. Reweighting sparse regularization is adopted to enhance the sparsity in the solution. Simulation studies on a planar frame and a simply supported overhanging beam show that the sparse regularization exhibits certain superiority over Tikhonov regularization as less false‐positive errors exist in damage identification results. The experimental result of the overhanging beam further demonstrates the effectiveness and superiorities of the sparse regularization in response sensitivity‐based damage identification. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-09-03T02:43:50.076041-05:
      DOI: 10.1002/stc.1785
  • System identification of a full‐scale five‐story reinforced
           concrete building tested on the NEES‐UCSD shake table
    • Abstract: This paper presents the identification of modal properties of a full‐scale five‐story reinforced concrete building fully outfitted with nonstructural components and systems (NCSs) tested on the NEES‐UCSD shake table. The fixed base building is subjected to a sequence of earthquake motions selected to progressively damage the structure and NCSs. Between seismic tests, ambient vibration response is recorded. Additionally, low‐amplitude white noise (WN) base excitation tests are conducted during the test protocol. Using the vibration data recorded, five state‐of‐the‐art system identification (SID) methods are employed, including three output‐only and two input‐output. These methods are used to estimate the modal properties of an equivalent viscously‐damped linear elastic time‐invariant model of the building at different levels of damage and their results compared. The results show that modal properties identified from different methods are in good agreement and that the estimated modal parameters are affected by the amplitude of excitation and structural/nonstructural damage. Detailed visual inspections of damage performed between the seismic tests permit correlation of the identified modal parameters with the actual damage. The identified natural frequencies are used to determine the progressive loss of apparent global stiffness of the building, and the state‐space models identified using WN test data are employed to investigate the relative modal contributions to the measured building response at different damage states. This research provides a unique opportunity to investigate the performance of different SID methods when applied to vibration data recorded in a real building subjected to progressive damage induced by a realistic source of dynamic excitation. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-28T01:52:05.397971-05:
      DOI: 10.1002/stc.1778
  • Identification of spatio‐temporal distribution of vehicle loads on
           long‐span bridges using computer vision technology
    • Authors: Zhicheng Chen; Hui Li, Yuequan Bao, Na Li, Yao Jin
      Abstract: Identification of spatio‐temporal distribution of vehicle loads is very important for understanding the exact loading conditions and behaviors of long‐span bridges. Using computer vision technology combining the monitoring information of the weigh‐in‐motion system (WIM) at one cross‐section and the camera along the bridge, a method to identify the spatio‐temporal distribution of vehicle loads for long‐span bridges is proposed. For moving vehicles, template images were sampled from the camera video at the location of the WIM, and the weight information of the captured vehicle was extracted from the output data sheet of the WIM based on the relationship of the pass time. Template matching and particle filter techniques were used to track the moving vehicle loads on the bridge. The images were processed using the computer vision technology. The video images obtained from cameras and the weight information measured by the WIM on the Hangzhou Bay Bridge were employed in this study. The effectiveness and accuracy of the proposed algorithm were validated through the in situ field test results on the Hangzhou Bay Bridge. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-25T00:18:05.729872-05:
      DOI: 10.1002/stc.1780
  • Assessment of mechanical properties of full‐scale masonry panels
           through sonic methods. Comparison with mechanical destructive tests
    • Abstract: Sonic tests are a valid and useful non‐destructive method for qualitative characterization of masonry elements. If sonic tests are applied with the right configuration, the results can identify discontinuities in masonry sections and provide the morphology of a construction typology, contributing to the assessment of built heritage as demanded by the international recommendations on this domain. The elaboration of data from sonic tests applied to masonry structures has been essentially based on the evaluation of the P waves' propagation through the masonry thickness, that is, by using the direct sonic method, a procedure that has been calibrated for many years by different authors. However, recent studies have shown that indirect configurations through the indirect sonic impact method may be used to estimate the mechanical properties of stones masonry samples. This procedure allows assessing not only P but also R wave propagation, permitting to estimate the deformability characteristics of masonry panels. Under this research, a set of stone masonry specimens was tested using both direct and indirect sonic impact methods and later assessed through laboratory mechanical compression tests, a procedure's sequence that allow validating the sonic tests capabilities. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-25T00:09:09.99442-05:0
      DOI: 10.1002/stc.1783
  • A local excitation and measurement approach for decentralized damage
           detection using transmissibility functions
    • Authors: Dapeng Zhu; Xiaohua Yi, Yang Wang
      Abstract: In order to assess structural safety conditions, many vibration‐based damage detection methods have been developed in recent years. Among these methods, transmissibility function analysis can offer advantages in easy and low‐cost implementation, as well as independency to the magnitude and waveform of an excitation record. Harnessing these features, a decentralized structural damage detection procedure is proposed in this paper. The proposed procedure only requires measurements in one small area at a time, and thus, is ideal for using limited number of sensors upon a large‐scale structure. This study also investigates the nature of transmissibility functions for damage detection in an analytical manner, based on a chain‐like spring–mass–damper system with multiple degrees‐of‐freedom. The analytical derivation is validated through numerical simulation and laboratory experiments using mobile sensors. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-20T00:01:04.28997-05:0
      DOI: 10.1002/stc.1781
  • Efficient time synchronization for structural health monitoring using
           wireless smart sensor networks
    • Authors: Jian Li; Kirill A. Mechitov, Robin E. Kim, Billie F. Spencer
      Abstract: Wireless smart sensor networks (WSSNs) have shown great promise in structural health monitoring (SHM), because of their advantages of low cost, higher flexibility, robust data management, and ability to provide better understanding of structural behavior through dense deployment of sensors. However, implementation of wireless SHM systems poses many challenges, one of which is ensuring adequate synchronization of the collected data. This issue arises in WSSNs because each smart sensor in the network having an independent processor with its own local clock, and this clock is not necessarily synchronized with the clocks of other sensors. Moreover, even though the clocks can be accurately synchronized by exchanging time information through beacon messages, the measured data may still be poorly synchronized because of random delays from both software and hardware sources; that is, synchronized clocks do not necessarily yield synchronized sensing. Various algorithms have been proposed to achieve both synchronized clocks and sensing. However, these protocols still lack the desired performance for SHM applications for reasons of extended data collection time, temperature variations resulting in nonlinear clock drift, requirement for prompt response, and so on. In this paper, the unique features and challenges of synchronized sensing for SHM applications are discussed, followed by a numerical investigation of the effect of nonlinear clock drift on data synchronization accuracy. A new synchronized sensing strategy considering nonlinear clock drift compensation is proposed with two different implementations to meet various application requirements. Experimental results show that the proposed time synchronization approach can compensate for temperature effects on clock drift and provide efficient and accurately synchronized sensing (
      PubDate: 2015-08-19T01:24:14.864217-05:
      DOI: 10.1002/stc.1782
  • Assessment of wood structural members degradation by means of infrared
           spectroscopy: an overview
    • Authors: Anna Sandak; Jakub Sandak, Mariapaola Riggio
      Abstract: Timber structures can undergo alteration during their service life, which can be caused by mechanical, environmental or biological agents (bacteria, fungi and insects), because of the biological nature of the material. On site characterization of timber members is a very challenging task, especially assuming that both, the structure itself and material used for construction have to be evaluated. Current assessment procedures are limited to visual inspection, occasionally supported by a few instrumental analyses (such as wood moisture content measurement and drilling resistance tests). However, a clear tendency for the application of various non‐destructive techniques is observed nowadays. The paper presents an overview on the current applications of infrared spectroscopy for the characterization of various alteration phenomena in wooden artefacts. A literature review is complemented by a series of results, reported from experimental campaigns carried out by the authors. The aim of the paper is to demonstrate the applicability of the proposed method for the analysis of different degradation processes occurring in timber members, with a special attention on wood aging, weathering, biotic decay by fungi and waterlogging. Examples of spectra evaluation as well as limitation of proposed methods are presented. Case studies including classification of decay type, analysis of the weathering dynamic and characterization of waterlogged wooden samples are briefly illustrated. Practical application of spectroscopy within timber structure assessment is considered as a very important supplement to the typical information collected during ordinary tests. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-17T23:16:57.79287-05:0
      DOI: 10.1002/stc.1777
  • Optimal viscous dampers gains for structures subjected to earthquakes
    • Authors: Ido Halperin; Yuri Ribakov, Grigoriy Agranovich
      Abstract: Passive control is a known method for vibrations damping in civil structures. The simplicity and reliability of passive damping devices makes them a worthy candidate in many practical applications. However, despite of its practical simplicity, the optimal design of passive controller is quite a hard computational problem. In this work, an enhanced optimal viscous passive dampers design method is proposed for seismically excited structures. The optimization is carried out with relation to performance index that consists of an H2 norm of the system and a quadratic gains norm. An algorithm is suggested for the look after a candidate optimum. It is based on Newton's optimization method with recently developed effective calculation method for the Hessian matrix. Numerical evaluation of the suggested method demonstrates a very fast convergence rate of the design algorithm and proves a performance effective dampers distribution. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-17T22:52:49.1871-05:00
      DOI: 10.1002/stc.1779
  • Damage identification in aluminum beams using support vector machine:
           Numerical and experimental studies
    • Authors: Satish B. Satpal; Anirban Guha, Sauvik Banerjee
      Abstract: Support vector machine (SVM) has been established as a promising tool for classification and regression in many research fields recently. In the current research work, SVM is explored to find damage locations in aluminum beams using simulation data and experimental data. Displacement values corresponding to the first mode shape of the beam are used to predict the damage locations. Two boundary conditions namely fixed‐free and fixed‐fixed are considered for this study. Damages are introduced in the form of rectangular notches along the width of the beam at different locations. Numerical simulations using commercially available finite element (FE) package, Abaqus® are first carried out on beam and mode shape data is extracted to train and test SVM with and without noise in data. To validate the predictions of damage locations based on simulation data, actual experimentations are conducted on aluminum beams of identical dimensions and boundary conditions. In the experimental study, a Laser Doppler Vibrometer (LDV) is used to extract the mode shape data. It is shown that SVM is capable to predict damage locations with a good accuracy and can be used as a promising tool in the field of structural health monitoring (SHM). Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-08-06T12:17:51.190114-05:
      DOI: 10.1002/stc.1773
  • Semi‐active vibration control of structural systems based on a
           reference active control law: output emulation approach
    • Authors: Kazuhiko Hiramoto; Taichi Matsuoka, Katsuaki Sunakoda
      Abstract: A new semi‐active control strategy that approximates a predicted control output of a reference active control is proposed. A variable parameter of a semi‐active control device is selected at every time instant so that the predicted control output of the semi‐active control system becomes close to the corresponding predicted control output of the reference active control as much as possible. Parameters of the reference active control law are optimized in the premise of the aforementioned ‘output emulation’ strategy so that the control performance of the semi‐active control becomes good and the ‘error’ in the sense of achieved control performance between the reference active control and semi‐active control systems becomes small. A pole placement method based on a linear matrix inequality (LMI) framework is adopted as the reference active control law. Parameters to determine the domain in the complex plane where the closed‐loop poles are placed are searched so that control performance of the semi‐active control system based on the output emulation approach is optimized. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-31T02:28:19.16465-05:0
      DOI: 10.1002/stc.1770
  • Sparse representation of ultrasonic guided‐waves for robust damage
           detection in pipelines under varying environmental and operational
    • Authors: Matineh Eybpoosh; Mario Berges, Hae Young Noh
      Abstract: The challenges of guided‐wave based structural health monitoring can be discussed under three headings: (a) multiple modes, (b) multi‐path reflections, and (c) sensitivity to environmental and operational conditions (EOCs). The objective of this paper is to develop damage detection methods that simplify guided‐wave signals while retaining damage information and have low sensitivity to EOC variations. A supervised method is proposed for damage detection. The detection performance is maximized, by imposing a sparsity constraint on the signals. This paper reports a diverse set of laboratory and field experiments validating the extent to which EOC variations, as well as damage characteristics can influence the discriminatory power of the damage‐sensitive features. The laboratory setup includes an aluminum pipe with temperature varying between 24 and 38 ° C. The method is further validated using an operational hot water supply piping system of different size and configuration than the one used in the laboratory, which operates under noisy environment, with constantly varying flow rate, temperature, and inner pressure. Moreover, the proposed method is used to detect occurrence of consecutive actual damages, namely, a crack and a mass loss as small as 10% and 8% of the wall thickness, respectively. The validation results suggest that a simple binary‐labeled training data (i.e., undamaged/damaged), obtained under a limited range of EOCs, are sufficient for the proposed method. That is, the detection method does not require prior knowledge about the characteristics of the damage (e.g., size, type, and location), and/or a training dataset that is obtained from a wide range of EOCs. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-29T04:02:15.939173-05:
      DOI: 10.1002/stc.1776
  • Discussion of system intrinsic parameters of tuned mass dampers used for
           seismic response reduction
    • Authors: Julio C. Miranda
      Abstract: Assimilating the structures incorporating tuned mass dampers to 2‐degrees‐of‐freedom mechanical systems, this paper discusses the salient parameters defining the efficiency of these devices when affixed to structures for the purpose of seismic response reduction. Focusing on parameters that are intrinsic to the mechanical systems and independent of ground motions, numerical and analytical expressions are first obtained for the modal damping of the systems. Subsequently, it is proposed that the highest efficiency in terms of modal damping allocation is achieved at tuning that results in modal damping that is in the same proportion as the participation factors for the modes. Further, some properties of the frequencies, tuning, and participation factors are analytically demonstrated. Finally, limited numerical calculations using a spectrum‐compatible accelerogram are offered to support the proposed method for modal damping allocation. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-28T04:24:24.891963-05:
      DOI: 10.1002/stc.1775
  • Damage detection with small data set using energy‐based nonlinear
    • Abstract: This study proposes a new algorithm for damage detection in structures. The algorithm employs an energy‐based method to capture linear and nonlinear effects of damage on structural response. For more accurate detection, the proposed algorithm combines multiple damage sensitive features through a distance‐based method by using Mahalanobis distance. Hypothesis testing is employed as the statistical data analysis technique for uncertainty quantification associated with damage detection. Both the distance‐based and the data analysis methods have been chosen to deal with small size data sets. Finally, the efficacy and robustness of the algorithm are experimentally validated by testing a steel laboratory prototype, and the results show that the proposed method can effectively detect and localize the defects. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-28T04:16:45.773728-05:
      DOI: 10.1002/stc.1774
  • Investigating the use of Targeted‐Energy‐Transfer devices for
           stay‐cable vibration mitigation
    • Abstract: Free vibrations of a taut cable with an attached passive Targeted‐Energy‐Transfer (TET) device are investigated using an analytical formulation of the complex generalized eigenvalue problem. This problem is of considerable practical interest in the context of stay‐cable vibration suppression in bridges, induced by wind, rain–wind and parametric excitation. The TET device is a nonlinear apparatus, which has been investigated and successfully applied to the vibration suppression in several structural or mechanical systems. This study proposes, for the first time, the use of the TET device as a simple passive apparatus for stay‐cable vibration mitigation. In this application, the device was modelled as a dashpot with a viscous damper in parallel with a power‐law nonlinear elastic spring element and a lumped mass restrained to one end. The ‘flexibility of the support’ (imperfect anchorage to the deck) was also simulated by placing an elastic support (linear elastic spring) in series between the dashpot and the deck. The study derives a new family of ‘universal design curves’ for the TET device, by accounting for the effects of nonlinear elastic stiffness, lumped mass and flexibility of the support. To verify the adequacy of the universal curves and to evaluate the effectiveness of the TET devices, parametric numerical simulations were performed on a reference stay cable. As an application example, analytical results were employed to design the dampers of one flexible stay, installed on an existing cable‐stayed bridge. In all the investigations, theoretical and numerical results were obtained and compared. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-24T02:31:06.864642-05:
      DOI: 10.1002/stc.1772
  • Distributed fiber optic sensors for monitoring pressure and stiffness
           changes in out‐of‐round pipes
    • Authors: Kenneth Lim; Leslie Wong, Wing Kong Chiu, Jayantha Kodikara
      Abstract: Distributed fiber optic sensors have been shown to be promising when used to monitor the structural health of pipes. The body of work thus far has only considered pipes whose cross sections are assumed to remain circular under load. In some applications, the cross section of the pipe has been known to deform when loaded. Subsequent loading on a deformed pipe then generates additional stresses that may have been unaccounted for when designing the pipe. This paper addresses the effects of the initial non‐circular cross section of a pipe under internal pressure and its detection with a distributed fiber optic sensor based on Brillouin Optical Time Domain Analysis. This ability of the Brillouin Optical Time Domain Analysis sensor to detect local stiffness irregularities on an out‐of‐round pipe subjected to internal pressures is also demonstrated. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-15T02:06:13.682052-05:
      DOI: 10.1002/stc.1771
  • A frequency response‐based structural damage identification using
           model updating method
    • Authors: Fariba Shadan; Faramarz Khoshnoudian, Akbar Esfandiari
      Abstract: Structural model updating by estimation of stiffness and mass parameters via monitoring of dynamic characteristics has attracted much attention in recent decades. In this study, frequency response functions (FRF) are utilized in order to identify unknown structural parameters using a sensitivity‐based model updating approach. A sensitivity equation that diminishes adverse effects of incompleteness of FRF data is proposed for model updating. Efficiency of the proposed method and impacts of measurement errors and incompleteness of measured data are examined numerically through a truss reference example. The stiffness and mass parameters of the intact model are updated using the damped FRFs of the simulated damaged model. The results demonstrate that the proposed method is capable of precisely identifying the location and the severity of damage in all studied cases. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-14T09:47:44.800343-05:
      DOI: 10.1002/stc.1768
  • Hybrid two‐step method of damage detection for plate‐like
    • Abstract: This paper develops a two‐step approach for structural damage detection. In the first step, the two‐dimensional generalized local entropy (2D‐GLE) is proposed to identify the damage location and number for plates. Based on the 2D‐GLE, singularities in plates are revealed with the aid of mode shapes; hence, damages are localized, and the number of which is estimated. Besides, the statistical analysis is applied in the analysis of 2D‐GLE damage maps to overcome the difficulty in damage detection methods without baseline data. In the second step, the damage severities at the identified locations are evaluated via the optimization using artificial bee colony (ABC) with the designed frequency object function. The advantages of the present method are as follows: (1) No‐baseline in the measurement of mode shapes. Damage localization via the 2D‐GLE avoids using healthy mode shapes serving as baselines in damage detection, and then only damaged mode shapes are required. (2) No down‐sampling. Compared with the wavelet‐based methods, no down‐sampling enhances the algorithmic robustness and accuracy. (3) Efficiency. This hybrid two‐step method shrinks the solving parameter domain sharply in optimization via the first step. Hence, only the severity parameters need to be investigated in ABC. (4) Robustness. ABC ensures the robustness of the proposed method. Different damage cases are investigated in simulations, single‐damage/multiple‐damage cases, and noise immunity tests demonstrate that the proposed method is effective and accurate in damage detection. At last, a simple experiment is given to verify the present algorithm. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-07-03T01:23:13.385038-05:
      DOI: 10.1002/stc.1769
  • Performance improvement method of support vector machine‐based model
           monitoring dam safety
    • Authors: Huaizhi Su; Zhexin Chen, Zhiping Wen
      Abstract: Under the comprehensive influence of material and loads, dam structural behavior presents the time‐varying nonlinear characteristics. To forecast the dam structural behavior (displacement, stress, seepage, etc.), the models monitoring dam safety are often built according to the prototype observations on dam safety. However, the modeling process is usually fulfilled with the offline and static pattern. As time goes on, the fitting and forecasting ability of built static model will decline gradually. The article is focused on the support vector machine (SVM)‐based model monitoring dam safety. The methods are studied to advance the adaptability of SVM model and reduce the modeling time. By implementing the impact analysis for SVM parameters and input vector, the optimization method of SVM parameters and input vector is presented to enhance the efficiency of building the SVM‐based static model monitoring dam safety. To describe dynamically the time‐varying mapping relationship between dam structural behavior (effect‐quantity) and its cause (influence‐quantity), the way is developed to update in real time above model by making the most use of new observations. The displacement of one actual dam is taken as an example to verify the modeling efficiency and forecasting ability. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-29T02:26:52.134791-05:
      DOI: 10.1002/stc.1767
  • Fatigue sensor for structural health monitoring: Design, fabrication and
           experimental testing of a prototype sensor
    • Authors: Subash Gokanakonda; Muralidhar K. Ghantasala, Daniel Kujawski
      Abstract: Fatigue damage monitoring of any structure is a prerequisite for reliable and effective structural health prognosis. A novel fatigue sensor for detecting and monitoring the fatigue damage and estimating the remaining life of machine components and structures subjected to cyclic loads is discussed. The fatigue sensor consists of alternate slots and strips having different strain magnification factors with respect to the nominal strain at the location where it is placed on the structure. The sensor experiences the strains which closely resemble the actual strain distribution in the critical area of the component. The sensor can be placed away from the notch‐root stress concentration region at a convenient location on the structure but would still experience the same fatigue damage as the notch‐root. The strips fail in a sequential manner from the strip experiencing the highest strain magnification to the lowest. Each strip failure corresponds to the particular fatigue damage accumulated by the structure being diagnosed. This information allows for predicting remaining component life. The design of the fatigue sensor is validated by the elastic and elastic‐plastic finite element analysis simulations. The finite element analysis (FEA) simulations were performed in 2D and 3D configurations. This paper describes different aspects of the fatigue sensor design, analytical modeling, FEA simulation, fabrication, and experimental testing along with the results. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-19T01:24:16.826451-05:
      DOI: 10.1002/stc.1765
  • An improved substructural damage detection approach of shear structure
           based on ARMAX model residual
    • Authors: Liu Mei; Akira Mita, Jin Zhou
      Abstract: In this paper, an improved substructure‐based damage detection approach is proposed to locate and quantify damages in a shear structure, which extends from a previously established substructure approach. This method requires only three sensors to locate and quantify the damage in any story of a shear structure building. Similarly, as in the previous approach, a substructure approach is adopted in the improved procedure to divide a complete structure into several substructures. To improve the noise immunity and damage detection robustness under different types of excitations and realistic conditions, this paper proposes an autoregressive‐moving average with exogenous inputs (ARMAX) model residual‐based technique to correct the former damage indicator. The correction coefficient is defined as the normalized Kolmogorov–Smirnov (KS) test statistical distance between the two distinguished data sets of ARMAX model residual generalized from input–output data process for undamaged and damaged states. To better assess the performance of the improved procedure, simulation and experimental verifications of the proposed approach have been conducted, and the results are compared with the previous method. It shows that the improved procedure works much better and more stable than the previous method especially when it is applied to realistic problems. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-16T02:55:29.803503-05:
      DOI: 10.1002/stc.1766
  • Impact damage identification in composite skin‐stiffener structures
           based on modal curvatures
    • Abstract: The feasibility of a vibration‐based damage identification approach for impact damage in two advanced composite skin‐stiffener structures is investigated in this paper. Mode shape curvatures combined with the modal strain energy damage index (MSE‐DI) algorithm are utilized to identify the damage. Special attention is paid to the effective application of this vibration‐based methodology by investigating the relation between the damage location, the structural design, and the dynamic behavior. The performance of a 1D and 2D formulation of the MSE‐DI algorithm is compared for several damage scenarios. Experiments demonstrated the capabilities of the MSE‐DI algorithm to detect, localize, and roughly quantify the size of barely visible impact damage in advanced composite structures. It is concluded that the method is particularly effective for health monitoring of skin‐stiffener connections. The most effective results were obtained by considering the 1D formulation in the direction of the stiffeners for the stiffener mid‐section and perpendicular to the stiffeners for the stiffener run‐out. The method remained inconclusive in the case of pure skin‐related damage. The results obtained in this study contribute to the development of guidelines for vibration‐based structural health monitoring of advanced composite skin‐stiffener structures. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-08T01:39:50.995135-05:
      DOI: 10.1002/stc.1754
  • A degree of dispersion‐based damage localization method
    • Abstract: We present an efficient and robust damage localization method. Its applications therefore include defect location in shear buildings and beam structures. The proposed method is based on the knowledge of the difference of curvatures, computed for a structure before and after damage occurs. However, instead of using modal shapes for this purpose, as is frequently performed, the present method computes the curvature directly from acceleration signals, without identifying modal shapes of the structure. Additionally, the accelerations are subjected to averaging, which reduces measurement noise, and logarithm extraction, which renders the method independent of the amplitude of the loading impulse used for damage location. Another important feature of the method is that it does not require any calibration of numerical models, because it is solely based on measurement data. The presented method of damage location is illustrated with two examples, which involve experimental tests on laboratory‐scale structures. The first example concerns defect location in a shear‐building structure, and the second one in a spatially excited simply supported steel beam. Both cases confirm the effectiveness of the method, and its robustness to measurement noise. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-04T21:52:20.000873-05:
      DOI: 10.1002/stc.1760
  • Unscented Kalman filter with unknown input and weighted global iteration
           for health assessment of large structural systems
    • Abstract: A novel concept denoted as unscented Kalman filter with unknown input and weighted global iterations (UKF‐UI‐WGI) to assess health of large structural systems is proposed. It incorporates the basic features of UKF to identify systems in the presence of severe nonlinearity but then added a few desirable features to increase its implementation potential. Because the information on excitation and unknown initial state vector is necessary to implement any UKF‐based approach, a substructure concept is introduced to generate them. The traditional UKF concept attempts to identify small structural systems using large duration of response histories in one global iteration. Because it fails to assess the defective states of large structures in most cases, a weighted multiple global iterations procedure with objective functions using short duration responses is introduced. The superiority of UKF‐UI‐WGI over the traditional UKF is demonstrated with the help of several illustrative examples using single and multiple substructures in identifying both defect‐free and defective states. With the help of the same examples, the superiority of the proposed method over the extended Kalman filter‐based method developed by the team earlier is conclusively documented. With the help of parametric studies, it is documented that the proposed method is robust, accurate, and stable. The study confirms that UKF‐UI‐WGI can identify large structural system using only limited response information measured at a small part of a structure without using any excitation information. The concept significantly advances the state‐of‐the‐art in UKF‐based nonlinear system identification and considerably improves its implementation potential. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-04T20:56:39.419163-05:
      DOI: 10.1002/stc.1764
  • Sparse l1 optimization‐based identification approach for the
           distribution of moving heavy vehicle loads on cable‐stayed bridges
    • Authors: Yuequan Bao; Hui Li, Zhicheng Chen, Fujian Zhang, Anxin Guo
      Abstract: A method for identifying the distribution of moving heavy vehicle loads is proposed for cable‐stayed bridges based on a sparse l1 optimization technique. This method is inspired by the recently developed compressive sensing (CS) theory, which is a technique for obtaining sparse signal representations for underdetermined linear measurement equations. In this study, sparse l1 optimization is employed to localize the moving heavy vehicle loads of cable‐stayed bridges through cable force measurements. First, a simplified equivalent load of vehicles on cable‐stayed bridges is presented. Then, the relationship between the cable forces and the moving heavy vehicle loads is established based on the influence lines. With the hypothesis of a sparse distribution of vehicle loads on the bridge deck (which is practical for long‐span bridges), moving heavy vehicle loads are identified by minimizing the ‘l2‐norm'of the difference between the observed and simulated cable forces caused by the moving vehicles penalized by the ‘l1‐norm’ of the moving heavy vehicle load vector. A numerical example of an actual cable‐stayed bridge is employed to verify the proposed method. The robustness and accuracy of this identification approach (with measurement noise for multi‐vehicle spatial localization) are validated. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-04T00:52:50.42359-05:0
      DOI: 10.1002/stc.1763
  • The hybrid multivariate analysis method for damage detection
    • Abstract: As the defects and superiorities of indices are mutualisms frequently, such as noise immunity and damage sensitivity, damage identification based on single damage index may hardly present the effective result all the time, so multiple indices fusion method is introduced in this paper to achieve some complementary improvements. In this paper, two kinds of no‐baseline mode shape‐based damage indices, namely, the generalized local entropy and the curvature waveform capacity fractural, are utilized to construct the basic index set for combination, and the fuzzy cluster method is introduced in order to establish fusion process. These two parts generate the hybrid multivariate analysis method finally. The multivariate analysis' superiority mainly displays on two aspects: (1) the use of no‐baseline mode shape‐based method ensures the damage detection efficiency with the absence of healthy mode shape serving as baseline and (2) the fusion conducted by cluster method provides the mutual support and complementation among indices, which can enhance the robustness of algorithm. The performances of the present method are verified via sufficient numerical examples, and then experiments are demonstrated on three typical engineering structures, namely, cantilever beam, blower wheel, and rotor, for further validations. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-02T00:57:11.055756-05:
      DOI: 10.1002/stc.1758
  • Friction estimation in wind turbine blade bearings
    • Abstract: The influence of friction on wind turbines (WTs) is often seen as undesirable as it has been proven to be the root cause of different severe damages, where the most vulnerable WT's components are bearings. Accurate modelling and identification of friction affects are thus required in order to characterise frictional behaviour and prevent severe damages. This paper addresses the problem on the real‐time estimation of friction levels that vary in time with different rates in the WT's blade bearings. Because of ageing or damage progression in bearings, friction parameters change in time. Knowing the material properties and a damage model, monitoring of the friction can be used for condition monitoring of WT's blade bearings. The considered nonlinear identification methods suitable for estimation of fast varying parameters are the extended Kalman filter (EKF), the unscented Kalman filter, the particle filter (PF) and the PF combined with the EKF. This paper also proposes a novel modification of a differential evolution algorithm for the identification of parameters that slowly vary in time. The main contribution of this paper is the algorithm, which combines the modified differential evolution algorithm with optimal nonlinear filters for the estimation of parameters which vary at different rates. A LuGre friction model and a realistic WT sensor setup are selected. The techniques are benchmarked against simulated WT data, and their performances are compared and discussed. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-06-01T02:26:07.202124-05:
      DOI: 10.1002/stc.1752
  • Modal identification of damaged frames
    • Authors: Mariella Diaferio; Vincenzo Sepe
      Abstract: The paper investigates the possibility of identifying localised damages for multi‐span and multi‐floor linear elastic frames using only natural frequencies measured in the undamaged and damaged configurations. Namely, frames of increasing complexity are studied by exploring one by one their significant substructures (i.e. multi‐span beams, floor by floor); the error function is defined and minimised on a database of finite element damaged models that only includes the natural frequencies of the local modes of the substructure, that is, the only modes significantly affected by the localised damage considered here. The performances and limits of the procedure are here discussed by means of numerical simulations on steel frames of increasing complexity; a particular attention is also devoted to the role of noise on the identification procedure. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-29T11:22:34.482893-05:
      DOI: 10.1002/stc.1762
  • Structural health monitoring of a damaged church: design of an integrated
           platform of electronic instrumentation, data acquisition and client/server
    • Abstract: A practical view is provided on the integration of electronic instrumentation, data acquisition, and software development systems applied to the analysis of pathological structural processes. This system will enable researchers to remotely monitor constructions; compile a register of historical data, creating files for postprocessing; and establish computer‐based protocols for evaluation of information, defining automatic alarms when the monitored data exceed preset limit values. This integration is based on the implementation of a remote terminal unit architecture in an industrial PC along with some other elements, namely, the following: suitable data acquisition cards for the type of sensors used, which continuously collect the data the sensors gather; the installation of an application server that periodically communicates with the system, extracting data while guaranteeing persistence; and finally, a web server, which provides remote access to both the data themselves and the system configuration, using a client application developed in JavaFX, a platform for developing rich Internet applications. As an example of the integration, the architecture of a system deployed in a Church in Comillas, Spain, is shown. The work carried out related to the register of existing damage is reported in order to explain the choice of the zones for deployment of the monitoring devices as well as the tasks involved in the installation of the sensors and other devices. Finally, the evolution is presented of the measurements taken during more than 1.5 years of monitoring, as well as their validation through comparison with those obtained by discrete in situ measurement. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-26T01:03:09.644758-05:
      DOI: 10.1002/stc.1759
  • Damage detection of SFRC concrete beams subjected to pure torsion by
           integrating acoustic emission and Weibull damage function
    • Authors: Arash Behnia; Hwa K. Chai, Navid Ranjbar, Mohd Z. Jumaat
      Abstract: In some cases, torsion is the dominant or critical factor contributing to the failure of a concrete member. This research proposes a novel damage detection method for fiber‐reinforced concrete beams subjected to pure torsion loading by statistical analysis of acoustic emission (AE) data. Concrete beams with varying water/cement ratios and different fiber volume fractions were subjected to pure torsion during AE monitoring. It was found that the cumulative AE event with respect to the twist angle correlated well to the mechanical loading. A Weibull rupture probability distribution is introduced to quantitatively predict the mechanical damage behavior under pure torsion. A bi‐logarithmic regression analysis is carried out to calibrate the Weibull damage distribution function with the detected AE data in order to characterize the torsion fracture process. Moreover, a quantitative approach by means of b‐value results is presented in this article to further analyze damage and fracture process. Torsion fracture properties were correlated to the AE parameters, and it was shown that the magnitudes of AE parameters were influenced significantly by mechanical properties of specimens. Therefore, AE would be suitable to describe the fracture of concrete specimens subjected to torsion. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-26T01:00:14.28364-05:0
      DOI: 10.1002/stc.1753
  • Vision‐based algorithms for damage detection and localization in
           structural health monitoring
    • Authors: Ziemowit Dworakowski; Piotr Kohut, Alberto Gallina, Krzysztof Holak, Tadeusz Uhl
      Abstract: Deflection curve can be used to detect and localize damage in civil engineering structures. In this paper, a vision‐based method applied for in‐plane displacement field measurement of cantilever beams is presented. The deflection curve of the analyzed structure is computed by means of the digital image correlation. Damage is introduced into the structure. Resulting deflection curves are used as an input to the novel damage detection algorithms: line segments method and voting method. The algorithms are then compared with the second derivative method and assessed through the probability of detection procedure. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-26T00:59:18.360237-05:
      DOI: 10.1002/stc.1755
  • Benchmark problem in active structural control with wireless sensor
    • Authors: Zhuoxiong Sun; Bo Li, Shirley J. Dyke, Chenyang Lu, Lauren Linderman
      Abstract: Structural control systems offer an attractive approach to protect civil infrastructures from natural hazards such as earthquakes. Wireless structural control systems that utilize wireless sensors for sensing, communication, and control have drawn increased attention because of the flexible installation, rapid deployment, and reduced cost. Although there are studies of wireless control systems for civil structures, a benchmark problem that captures not only the dynamics of the plant but also the realistic features of a wireless network has not been available. In this paper, a benchmark model for an active mass driver system with a wireless sensor network is presented. This wireless control benchmark model combines a seismically excited building benchmark model developed with Simulink (Matlab, MathWorks, Inc., Natick, MA, USA) and a wireless sensor network implemented in simulation using a state‐of‐the‐art wireless simulator TOSSIM (UC Berkeley, Berkeley, CA, USA). Wireless signal and noise traces collected from a real‐world multistory building are used as inputs to TOSSIM to realistically simulate the wireless sensor network. Wireless control design issues such as network‐induced delay, data loss, available sensor measurements, measurement noises, and control constraints can be studied with this benchmark model. A sample controller is provided to illustrate the wireless control design. Evaluation criteria have been provided to examine resources and control performances. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-23T09:01:27.256493-05:
      DOI: 10.1002/stc.1761
  • A lower bound for the variance of frequency and damping ratio identified
           from noisy vibration measurements
    • Abstract: This paper derives exact expressions to compute the lowest achievable variance by any unbiased estimator of modal frequency and damping ratio from free vibration and forced vibration signals contaminated by additive zero‐mean Gaussian white noise. These limits are found through the Cramer–Rao lower bound theory. The paper presents simulated system identification results that confirm the applicability of the derived expressions. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-23T09:00:18.6706-05:00
      DOI: 10.1002/stc.1757
  • An inverse parallel genetic algorithm for the identification of skin/core
           debonding in honeycomb aluminium panels
    • Authors: V. Meruane; V. Fierro
      Abstract: Honeycomb sandwich structures are used in a wide variety of applications. Nevertheless, because of manufacturing defects or impact loads, these structures can experience imperfect bonding or debonding between the skin and the honeycomb core. Instances of debonding reduce the bending stiffness of the composite panel, which causes detectable changes in its vibration characteristics. This article presents a new methodology to identify debonded regions in aluminium honeycomb panels that uses an inverse algorithm based on parallel genetic algorithms. The honeycomb panels are modelled with finite elements using a simplified three‐layer shell model. The adhesive layer between the skin and core is modelled using linear springs, with reduced rigidity for the debonded sectors. The algorithm is validated using experimental data from an aluminium honeycomb panel containing different damage scenarios. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-18T03:26:30.546239-05:
      DOI: 10.1002/stc.1756
  • Deflection monitoring and assessment for a suspension bridge using a
           connected pipe system: a case study in China
    • Authors: Yang Liu; Yang Deng, C. S. Cai
      Abstract: This paper discusses the application of a connected pipe system (CPS) to a suspension bridge in China for the purpose of vertical deflection monitoring and assessment. The CPS mainly consists of three main parts: the pressure transmitters to detect the height change of liquid, the pipes to connect the reference point and measurement points, and the liquid to fill the connected pipes. Multiple pressure transmitters, taken as the measurement point, were mounted inside of the girder. A reference transmitter was mounted inside of a tower, taken as a fixed point. To verify the performance and reliability of the CPS, a controlled load test after the completion of the bridge construction and an uncontrolled load test under the actual traffic loading were carried out. The results showed that the CPS exhibited excellent capability in real‐time measurement of vertical deflection of the suspension bridge. With the long‐term deflection data monitored by the CPS, the extreme deflections with respect to vehicle loads were predicted by extreme value analysis. The generalized extreme value distribution was adopted to establish the probability models of the daily maximum and minimum deflection sequences, and then the extreme deflections within the design reference period of 100 years were determined based on the probability models. Comparison of the extreme deflections and the deflection thresholds was carried out. The deflection monitoring and assessment method proposed in this paper have shown high potential of applicability in the practice of health monitoring for long‐span bridges. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-05-12T23:43:05.950906-05:
      DOI: 10.1002/stc.1751
  • Bridge damage detection using ambient traffic and moving force
    • Authors: Eugene OBrien; Ciaran Carey, Jennifer Keenahan
      Abstract: This paper investigates a novel method for damage detection using a moving force identification algorithm. The method aims to detect the changes in the predicted forces applied by vehicles crossing a bridge, which are shown to be sensitive to damage. A two‐dimensional vehicle–bridge interaction model is used in theoretical simulations to assess the effectiveness of the method in detecting changes in stiffness. Fleets of similar vehicles are simulated, and the force pattern of greatest frequency is used as the damage indicator. Results indicate that the method is more sensitive to damage than direct measurements of displacement and can detect a loss in stiffness due to a crack with a depth of as little as 6% of the beam depth. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-04-27T04:51:00.099933-05:
      DOI: 10.1002/stc.1749
  • Robust force tracking control scheme for MR dampers
    • Authors: Felix Weber
      Abstract: This paper describes a novel force tracking control scheme for magnetorheological (MR) dampers. The feed forward, which is derived by a control‐oriented mapping approach to reduce modelling effort of the inverse MR damper behaviour, compensates for the main steady‐state nonlinearity of the MR damper force and thereby linearizes the plant. The resulting force tracking error due to model imperfections and parameter uncertainties is reduced by parallel proportional and integral feedback gains that are formulated based on the absolute values of actual MR damper force and desired control force due to the semi‐active constraint of the MR damper force. The feedback is enriched by an anti‐reset windup to account for MR damper current constraints and the concept of current reversal to accelerate demagnetization. The experimental validations of the force tracking control scheme on a rotational and a long‐stroke MR damper demonstrate its robustness and efficacy. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-04-14T00:58:23.226712-05:
      DOI: 10.1002/stc.1750
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