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  Subjects -> ENERGY (Total: 295 journals)
    - ENERGY (182 journals)
    - ENERGY: GENERAL (8 journals)
    - NUCLEAR ENERGY (26 journals)
    - PETROLEUM AND GAS (52 journals)
    - RENEWABLE ENERGY (27 journals)

ENERGY (182 journals)                  1 2 | Last

ActaEnergetica     Open Access  
Advances in Building Energy Research     Hybrid Journal   (Followers: 14)
Advances in Energy and Power     Open Access   (Followers: 5)
Advances in High Energy Physics     Open Access   (Followers: 16)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 17)
American Journal of Energy Research     Open Access   (Followers: 9)
Annals of Nuclear Energy     Hybrid Journal   (Followers: 8)
Annual Reports on NMR Spectroscopy     Full-text available via subscription   (Followers: 1)
Annual Review of Resource Economics     Full-text available via subscription   (Followers: 10)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Solar Energy     Hybrid Journal   (Followers: 14)
Archives of Thermodynamics     Open Access   (Followers: 6)
Artificial Photosynthesis     Open Access  
Asian Bulletin of Energy Economics and Technology     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: 8)
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: 18)
Carbon Management     Hybrid Journal   (Followers: 7)
Catalysis for Sustainable Energy     Open Access   (Followers: 4)
CERN courier. International journal of high energy physics     Free   (Followers: 4)
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: 16)
Electricity Journal     Partially Free   (Followers: 3)
Energy     Partially Free   (Followers: 27)
Energy & Fuels     Full-text available via subscription   (Followers: 25)
Energy and Buildings     Hybrid Journal   (Followers: 10)
Energy and Emission Control Technologies     Open Access   (Followers: 2)
Energy and Environment Focus     Free   (Followers: 3)
Energy and Environment Research     Open Access   (Followers: 12)
Energy and Environmental Engineering     Open Access   (Followers: 4)
Energy and Power     Open Access   (Followers: 8)
Energy and Power Engineering     Open Access   (Followers: 14)
Energy Conversion and Management     Hybrid Journal   (Followers: 10)
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: 4)
Energy Law Journal     Full-text available via subscription   (Followers: 4)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 17)
Energy Policy     Partially Free   (Followers: 52)
Energy Prices and Taxes     Full-text available via subscription   (Followers: 6)
Energy Procedia     Open Access   (Followers: 4)
Energy Reports     Open Access   (Followers: 3)
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: 14)
Energy Strategy Reviews     Partially Free   (Followers: 9)
Energy Studies Review     Open Access   (Followers: 5)
Energy Systems     Hybrid Journal   (Followers: 14)
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     Open Access   (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: 3)
IEEE Power and Energy     Full-text available via subscription   (Followers: 18)
IEEE Transactions on Energy Conversion     Hybrid Journal   (Followers: 11)
IEEE Transactions on Nuclear Science     Hybrid Journal   (Followers: 8)
IEEE Transactions on Power Systems     Hybrid Journal   (Followers: 19)
IET Power Electronics     Hybrid Journal   (Followers: 16)
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: 3)
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: 5)
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: 8)
International Journal of Energy and Statistics     Hybrid Journal  
International Journal of Energy Engineering     Open Access   (Followers: 13)
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)

        1 2 | Last

Journal Cover Structural Control and Health Monitoring
  [SJR: 1.351]   [H-I: 26]   [6 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1545-2255 - ISSN (Online) 1545-2263
   Published by John Wiley and Sons Homepage  [1597 journals]
  • A mode shape‐based damage detection approach using laser measurement
           from a vehicle crossing a simply supported bridge
    • Authors: Eugene J. OBrien; Abdollah Malekjafarian
      Abstract: This paper presents a novel algorithm for bridge damage detection based on the mode shapes estimated from a passing vehicle. The bridge response at the moving coordinate is measured from an instrumented vehicle with laser vibrometers and accelerometers. A modified version of the Short Time Frequency Domain Decomposition method is applied to the measured responses. The bridge mode shape is estimated with high resolution, which is appropriate for damage detection. A damage index based on mode shape squares is used to detect the presence and location of the damage. A numerical case study of a half‐car model passing over a bridge is described in this paper, which validates the performance of the proposed approach. Several damage scenarios are considered including different locations and severities. It is shown that the presence and location of the damage can be detected with acceptable accuracy when the vehicle is moving very slowly. In addition, the performance of the method using higher vehicle speeds is investigated and shows that the approach works well for speeds up to 8 m/s. The sensitivity of the algorithm to measurement noise is also studied by adding several levels of noise to the responses measured on the vehicle. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-02T03:40:11.514044-05:
      DOI: 10.1002/stc.1841
       
  • Extended discrete‐time transfer matrix approach to modeling and
           decentralized control of lattice‐based structures
    • Abstract: This paper presents the modeling and control of an aircraft wing structure constructed by lattice‐based cellular materials/components. A novel model reduction process is proposed that utilizes the extended discrete‐time transfer matrix method (E‐DT‐TMM). Through recursive application of the E‐DT‐TMM, an effective reduced‐order model can be obtained in which a decentralized discrete‐time linear quadratic regulator (LQR) controller can be designed. To demonstrate the efficiency of the proposed concept, a prototype wing structure is studied. The analysis and simulation results show that the performance of the proposed E‐DT‐TMM based decentralized LQR controller is comparable with that of the full‐state continuous LQR controller. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-01T03:03:07.159144-05:
      DOI: 10.1002/stc.1837
       
  • An analysis of pounding mitigation and stress waves in highway bridges
           
    • Authors: Suchao Li; Anxin Guo, Hui Li, Chenxi Mao
      Abstract: Seismic‐induced pounding between adjacent structures that are insufficiently separated can cause significant structural damage, even collapse, during severe earthquakes. This paper presents an experimental and numerical investigation into mitigating pounding on highway bridges using novel shape memory alloy pseudo‐rubber shock‐absorbing devices (SMAPR‐SADs). The mechanical properties and a theoretical model of SMAPR‐SADs are briefly introduced and investigated. Next, a series of shaking table tests on a 1:30 model of a steel highway bridge are conducted to investigate the effectiveness of the SMAPR‐SADs in mitigating the pounding of the structures. Based on the experimental results, the pounding‐induced stress waves are analyzed using wave theory and the cross‐wavelet transform method. Subsequently, numerical models of highway bridges with and without SMAPR‐SADs are proposed. The pounding mitigation mechanism of SMAPR‐SADs is analyzed using the momentum theorem, their ability to dissipate energy, and stress wave absorption theory. Two indexes representing the energy absorption and dissipation abilities of SMAPR‐SADs are proposed and investigated. Finally, the effect of the axial stiffness of SMAPR‐SADs on pounding mitigation is analyzed. The experimental and theoretical results demonstrate that SMAPR‐SADs are able to absorb energy stably and can significantly reduce the pounding response of highway bridges under seismic excitations. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-01T02:49:27.51003-05:0
      DOI: 10.1002/stc.1835
       
  • Suspension‐type tuned mass dampers with varying pendulum length to
           dissipate energy
    • Abstract: In this paper, an optimal energy dissipation control algorithm is applied into a semi‐active suspension‐type tuned mass damper (SA‐STMD) to suppress excessive vibration by means of variable pendulum length. The SA‐STMD mechanism consists of a mass block, a suspension rope, and a movable fulcrum that can be a short tube driven by a linear motor to vertically move along the suspension rope. As the fulcrum goes up, the pendulum length is extended, resulting in a smaller stiffness of the SA‐STMD, and vice versa. Accordingly, the restoring force in the SA‐STMD can be adjusted by varying the fulcrum positions. In the case where the energy dissipation ability by the original STMDs is insufficient, the movable fulcrum in the SA‐STMD system can compensate the STMDs for stiffness according to the proposed optimal energy dissipation control algorithm to provide controllable restoring forces. The controllable restoring forces are designed to act as viscous dampers that can make up for the lack of energy dissipation capacity. The numerical results from the time domain and frequency domain analyses show that the proposed approach utilizing the optimal energy dissipation control algorithm to adjust the pendulum length can induce controllable restoring forces with a butterfly‐shaped hysteresis loop, supplying a sufficient energy dissipation capacity to reduce responses to the unexpectedly large external vibration. Another potential benefit is cost reduction because of use of a less number of conventional viscous dampers in the STMD system. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-01T02:40:46.144104-05:
      DOI: 10.1002/stc.1834
       
  • Application of stochastic subspace identification for stay cables with an
           alternative stabilization diagram and hierarchical sifting process
    • Abstract: The modal parameters of numerous modes for a stay cable are usually required in engineering practice. The application of conventional stochastic subspace identification techniques without delicate cautions, however, has been found to be unsuccessful in this case. Aiming to attack such a difficulty, this study establishes a new methodology based on the covariance type of stochastic subspace identification for extensively identifying the modal parameters of a stay cable. Several details of choosing the parameters in performing stochastic subspace identification are first discussed. An important discovery is that the lower limit for setting the time lag parameter can be decided by the ratio of the fundamental period of cable to the sampling time increment for a valid identification with the conventional stabilization diagram. Inspired by the aforementioned criterion, an alternative stabilization diagram is further proposed to more conveniently distinguish stable modal parameters of cable. A hierarchical sifting process including three stages is then developed to systematically and automatically extract reliable modal parameters from the alternative stabilization diagram. Demonstrated by analyzing the ambient vibration measurements for three stay cables of Chi‐Lu Bridge, the feasibility of this new approach is verified with successfully obtaining the modal frequencies, damping ratios, and mode shape ratios for almost all the cable modes in the examined frequency range. Another interesting finding is that the modal frequencies and damping ratios of bridge deck can also be effectively identified from the ambient vibration signals of cable. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-28T02:30:18.749401-05:
      DOI: 10.1002/stc.1836
       
  • Mode shape‐based damage detection in plate structure without
           baseline data
    • Authors: Sandris Rucevskis; Rims Janeliukstis, Pavel Akishin, Andris Chate
      Abstract: In this paper, a mode shape curvature‐based method for detection and localization of damage in plate‐like structures is described. The proposed algorithm requires only the mode shape curvature data of the damaged structure. The damage index is defined as the absolute difference between the measured curvature of the damaged structure and the smoothed polynomial representing the curvature of the healthy structure. To examine the advantages and limitations of the proposed method, several sets of numerical simulations are carried out. Simulated test cases considering different levels of damage severity, measurement noise and sensor sparsity are studied to evaluate the robustness of the method under the noisy experimental data and limited sensor data. Applicability and effectiveness of the proposed damage detection method are further demonstrated experimentally on an aluminium plate containing mill‐cut damage. The modal frequencies and the corresponding mode shapes are obtained via finite element models for numerical simulations and by using a scanning laser vibrometer for the experimental study. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-20T03:34:01.608609-05:
      DOI: 10.1002/stc.1838
       
  • Bridge related damage quantification using unmanned aerial vehicle imagery
    • Authors: A. Ellenberg; A. Kontsos, F. Moon, I. Bartoli
      Abstract: Visual inspection procedures remain the primary method of infrastructure assessment throughout the USA, but their shortcomings are numerous. In addition to their widely acknowledged variability and subjectivity, the large scale of civil infrastructure systems presents expensive access and time requirements that constrain the frequency of visual inspections and result in poor temporal resolution, which hampers effective decision‐making. To overcome this challenge, the research reported herein aimed to assess the ability of computer algorithms together with imagery collected by unmanned aerial vehicles (UAV) to extract accurate and quantitative information to help inform infrastructure management decisions. Techniques such as homography and lens distortion correction are used in this article in a post‐processing framework that allows the use of color images obtained by UAVs for actual damage quantification measurements. The experiments described in this article utilize a UAV with a mounted camera and provide measurements from a representative infrastructure mockup with several simulated damage scenarios. Deformation measurements, change detection (related to structural features and the size of deterioration), and crack pattern identification were all analyzed. The results indicated that the developed post‐processing algorithms were able to extract quantitative information from UAV captured imagery. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-20T03:27:55.397696-05:
      DOI: 10.1002/stc.1831
       
  • Structural damage detection using wireless passive sensing platform based
           on RFID technology
    • Authors: Mateusz Lisowski; Przemyslaw Gonek, Jakub Korta, Tadeusz Uhl, Wieslaw J. Staszewski
      Abstract: A wireless and battery‐free passive sensing platform is proposed for structural damage detection. The platform is based on the radio‐frequency identification (RFID) technology, where a standard RFID transponder device serves as an interface between low‐power sensors – used for damage detection – and RFID reading devices. Sensor data are transmitted remotely from this sensing platform to a Personal Computer (PC) that controls the entire system. Energy harvesting is the major novelty of the proposed approach. The magnetic field produced by an antenna of the RFID reading device is used for energy harvesting. The platform supports different types of sensors that can be positioned in remote locations and used for structural damage detection. The sensing capability and the damage detection performance of the proposed system are demonstrated using two simple application examples, that is, vibration measurements in a beam‐like structure subjected to the force excitation and temperature measurements in a bearing that supports a rotating shaft. The results illustrate the great potential of the proposed sensing platform for structural health monitoring applications, particularly in remote, difficult‐access, or hazardous conditions. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-19T21:23:20.652087-05:
      DOI: 10.1002/stc.1826
       
  • Theoretical prediction of the dynamic behavior of rolling‐ball
           rubber‐layer isolation systems
    • Authors: Alessandra Fiore; Giuseppe Carlo Marano, Maria Gabriella Natale
      Abstract: This paper presents the results of a theoretical study carried out to characterize the dynamic behavior of a seismic isolation system consisting of steel‐rolling balls on rubber layers. This type of device reduces seismic hazard during earthquakes by decoupling the superstructure from the ground motion and by dissipating the energy in damping, thanks to the viscous‐elastic properties of the rubber. The behavior of the rolling balls on rubber layers isolation system is described by achieving suitable expressions for the resultant normal and shear forces acting in the device. In particular, it is shown how the resultant shear force is highly affected by the correct definition of the slip and stick regions, which develop at the steel‐rubber contact area. The analysis allows to identify the main parameters characterizing this type of device, furnishing a valid tool in order to correctly calculate some response quantities significantly influenced by the isolation system. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-19T21:23:04.823953-05:
      DOI: 10.1002/stc.1830
       
  • Posicast control of structures using MR dampers
    • Authors: Tarek Edrees Alqado; George Nikolakopoulos
      Abstract: In this article, a novel application of a semi active posicast control scheme for structures with magneto‐rheological (MR) dampers is presented. MR dampers are considered to be highly promising of semi‐active control systems, which are becoming increasingly popular for alleviating the effects of dynamic loads on civil engineering structures because they combine the merits of both passive and active control systems. The main contribution of this article relates to the design, application, tuning and performance evaluation of the novel posicast control scheme for structural control. The efficiency of the suggested control strategy was evaluated by performing numerical simulations of a benchmark three‐storey building with an MR damper, rigidly attached between the first floor and the ground. The damper's behaviour was simulated using the Bouc–Wen model. Seven evaluation criteria were used to assess the performance of the proposed posicast control scheme in reducing the excited structure's responses to dynamic loading. The simulation's results indicated that the posicast control scheme had significant advantages over conventional alternatives in terms of performance and efficiency. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-13T03:09:56.500907-05:
      DOI: 10.1002/stc.1832
       
  • Enhanced nonlinear crack‐wave interactions for structural damage
           detection based on guided ultrasonic waves
    • Authors: Kajetan Dziedziech; Lukasz Pieczonka, Piotr Kijanka, Wieslaw J Staszewski
      Abstract: The paper presents a new damage‐detection method based on nonlinear crack‐wave interaction. Low‐frequency vibration excitation is introduced to perturb damage, and high‐frequency interrogating wave is used to detect damage‐related nonlinearities. However, in contrast to other crack‐wave interaction approaches, localised wave packets are used for high‐frequency excitation. The synchronisation of the low‐frequency vibration with the interrogating high‐frequency wave packets is a key element of the proposed method. Numerical simulations and simple experimental tests in cracked aluminium beams are performed to demonstrate the method. The results show that the proposed method can detect and localise damage‐related and intrinsic nonlinearities, allowing for reliable damage detection. The method does not require baseline measurements representing an undamaged condition, and it is not sensitive to temperature variations. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-10T22:08:34.190044-05:
      DOI: 10.1002/stc.1828
       
  • Output‐only damage detection using vehicle‐induced
           displacement response and mode shape curvature index
    • Authors: Dongming Feng; Maria Q. Feng
      Abstract: Most of the existing bridge superstructure damage detection methods are based on acceleration or strain response due to ambient excitation. This paper proposes a bridge damage detection procedure that utilizes vehicle‐induced displacement response without requiring prior knowledge about the traffic excitation and road surface roughness. This study is partially motivated by the recent advances in convenient measurement of structural displacements enabled by video‐based sensors. Vehicle–bridge interaction analysis shows that when subjected to moving vehicles, the bridge displacement response is dominated by the first‐order mode component. This justifies the proposed damage detection method that only requires the first‐order mode shape curvature. While conventionally the mode shapes are extracted based on operational modal analysis, the first‐order mode shape is extracted by directly analyzing the power spectral density functions of measured bridge displacement responses under vehicle excitations. Numerical simulations are carried out to investigate the feasibility and performance of the proposed damage detection method using three damage scenarios including damage at single, double, and multiple locations, each involving several extents of damage defined by the reduction in element stiffness. The results reveal that all the damage cases can be successfully identified. Furthermore, the damage detection performance is evaluated for cases involving different classes of road surface roughness and less measurement points. The study demonstrates the potential of the proposed model‐free and time‐efficient method for damage detection of bridge structures. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-06T00:06:16.780407-05:
      DOI: 10.1002/stc.1829
       
  • Localized genetically optimized wavelet neural network for
           semi‐active control of buildings subjected to earthquake
    • Authors: S. M. A. Hashemi; H. Haji Kazemi, A. Karamodin
      Abstract: Control algorithm is one of the most important aspects in successful control of buildings against earthquake. In recent years, because of their capabilities, soft computing methods, stemmed from human brain abilities, have become of particular interest to researchers. In this paper, a wavelet neural network‐based semi‐active control model is proposed in order to provide accurately computed input voltage to the magneto rheological dampers to generate the optimum control force of structures. This model is optimized by a localized genetic algorithm and then applied to a nine‐story benchmark structure subjected to 1.5× El Centro earthquake. The results show an average of 43% reduction of maximum drift in the controlled structure versus the uncontrolled one. The capability of the controller is also validated by applying other far‐field and near‐field earthquakes. The capability and efficiency of the proposed model are demonstrated in terms of drift, acceleration and base shear reduction. The proposed wavelet neural network is also compared with a tangent hyperbolic‐based feed forward neural network, linear quadratic Gaussian, clipped optimal controller, and genetic algorithm‐based fuzzy inference systems to show the superiority of the proposed controller. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-05T23:44:08.115232-05:
      DOI: 10.1002/stc.1823
       
  • Issue Information
    • Pages: 393 - 395
      Abstract: No abstract is available for this article.
      PubDate: 2016-02-02T03:58:40.584501-05:
      DOI: 10.1002/stc.1788
       
  • On‐line unsupervised detection of early damage
    • Abstract: Structural health monitoring (SHM) strategies should ideally consist of continuous on‐line damage detection processes, which do not need to rely on the comparison of newly acquired data with baseline references, previously defined assuming that structural systems are undamaged and unchanged during a given period of time. The present paper addresses the topic of SHM and describes an original strategy for detecting damage in an early stage without relying on the definition of data references. This strategy resorts to the combination of two statistical learning methods. Neural networks were used to estimate the structural response, and clustering methods were adopted for automatically classifying the neural networks' estimation errors. To ensure an on‐line continuous process, these methods were sequentially applied in a moving windows process. The proposed original strategy was tested and validated on numerical and experimental data obtained from a cable‐stayed bridge. It proved highly robust to false detections and sensitive to early damage by detecting small stiffness reductions in single stay cables as well as the detachment of neoprene pads in anchoring devices, resorting only to a small amount of inexpensive sensors. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-12-28T04:44:07.530761-05:
      DOI: 10.1002/stc.1825
       
  • Algorithm for the analysis of deformations and stresses due to torsion in
           a metal beam from LIDAR data
    • Abstract: An interesting field for application of LIDAR technology is structural health monitoring, especially in the study of deformation and stress in the beams. In the beams, it is not only the deformation due to bending that is an issue of control but it is also important to check the deformation due to torsion, particularly in open cross sections such as I, U, L, which have a very low torsional strength. This paper presents a new algorithm for obtaining, automatically and separately, the deformations in a beam subjected to torsional and bending loading, respectively, from LIDAR data. With the values of the deformation found by the new developed algorithm, the shear stresses are obtained. The methodology presented in this paper has been tested with a real beam in a laboratory under different load situations. The results obtained from the algorithm were compared not only with measurements by direct methods but also with results obtained by FEM simulation of the 3D model of the beam. The results found by the new algorithm compare with the other methods; therefore, this verifies the validity of the method for applications of structural health monitoring of metal structures. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-12-28T04:42:02.095205-05:
      DOI: 10.1002/stc.1824
       
  • Real‐time hybrid simulation of multi‐story structures
           installed with tuned liquid damper
    • Abstract: As a low cost and maintenance energy‐absorbing device, tuned liquid damper (TLD) is being widely used to suppress structural vibration. In this paper, the real‐time hybrid simulation (RTHS) is employed to investigate the performance of TLD for controlling seismic responses of actual multi‐story structures, where the TLD is experimentally modeled as physical substructure and the multi‐story structure is numerically simulated as numerical substructure. Taking advantage of RTHS technique, a methodology for achieving full‐scale TLD experiments is developed through suitable similarity design; a new interaction force measurement method and a new dual explicit algorithm are embedded into RTHS system to enhance simulation capability. First, the seismic response of a two‐story structure installed with TLD is analyzed by applying RTHS. Correspondingly, the pure shaking table test is performed to assess the accuracy of the RTHS. Then, the effectiveness of TLD for structures with various numbers of floors and different structural properties is tested through RTHS by varying the simulation model of the numerical substructure. Finally, the effects of mass ratio and structural damping ratio on a given TLD‐structure system are investigated. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-12-22T01:35:55.73777-05:0
      DOI: 10.1002/stc.1822
       
  • Monitoring crowd load effect on typical ancient Tibetan building
    • Abstract: Tibetan heritage building has attracted attention from many people who have interest in its historical and cultural value. Many of these buildings are opened to visitors in recent years, and the live load from tourist becomes a problem with increasing number of visitors. A monitoring system has been installed in a typical ancient Tibetan timber building to collect data on the material stresses and deformations of structural components. Based on the data collected, a strategy is proposed to evaluate the component of structural response induced by crowd load. A statistical relationship is obtained between the effective temperature change and the recorded strain increment. Results show that the measured strain is closely related to the number of visitors, and this may form the basis for a method to further evaluate the safety and integrity of the structure. An experiment was conducted on a corridor of the building with random pedestrian loading to validate the proposed strategy with encouraging results. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-12-22T01:19:03.910174-05:
      DOI: 10.1002/stc.1821
       
  • 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
       
  • 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
           records
    • 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
           bridges
    • 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
       
 
 
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