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ENERGY (180 journals)                  1 2 | Last

Advances in Building Energy Research     Hybrid Journal   (Followers: 11)
Advances in Energy and Power     Open Access   (Followers: 2)
Advances in High Energy Physics     Open Access   (Followers: 12)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 14)
American Journal of Energy Research     Open Access   (Followers: 6)
Annals of Nuclear Energy     Hybrid Journal   (Followers: 7)
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: 10)
Applied Solar Energy     Hybrid Journal   (Followers: 12)
Archives of Thermodynamics     Open Access   (Followers: 4)
Artificial Photosynthesis     Open Access  
Atomic Energy     Hybrid Journal   (Followers: 5)
Atoms for Peace: an International Journal     Hybrid Journal   (Followers: 3)
Biofuels     Hybrid Journal   (Followers: 8)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 5)
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: 6)
Catalysis for Sustainable Energy     Open Access   (Followers: 2)
CERN courier. International journal of high energy physics     Free  
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: 2)
Continental Journal of Renewable Energy     Open Access   (Followers: 11)
Current Sustainable/Renewable Energy Reports     Hybrid Journal   (Followers: 4)
Dams and Reservoirs     Hybrid Journal   (Followers: 3)
Development of Energy Science     Open Access   (Followers: 3)
Distributed Generation & Alternative Energy Journal     Hybrid Journal   (Followers: 1)
E3S Web of Conferences     Open Access  
Economics and Policy of Energy and the Environment     Full-text available via subscription   (Followers: 3)
Electrical and Power Engineering Frontier     Open Access   (Followers: 9)
Electronic Journal of Energy & Environment     Open Access   (Followers: 9)
Energy     Partially Free   (Followers: 26)
Energy & Fuels     Full-text available via subscription   (Followers: 25)
Energy and Buildings     Hybrid Journal   (Followers: 7)
Energy and Environment Research     Open Access   (Followers: 9)
Energy and Environmental Engineering     Open Access  
Energy and Power     Open Access   (Followers: 3)
Energy and Power Engineering     Open Access   (Followers: 10)
Energy Conversion and Management     Hybrid Journal   (Followers: 8)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Harvesting and Systems : Materials, Mechanisms, Circuits and Storage     Hybrid Journal   (Followers: 1)
Energy Journal The     Full-text available via subscription  
Energy Law Journal     Full-text available via subscription   (Followers: 2)
Energy Policy     Partially Free   (Followers: 47)
Energy Prices and Taxes     Full-text available via subscription   (Followers: 5)
Energy Procedia     Open Access   (Followers: 3)
Energy Research & Social Science     Full-text available via subscription  
Energy Science & Engineering     Open Access   (Followers: 4)
Energy Science and Technology     Open Access   (Followers: 12)
Energy Strategy Reviews     Partially Free   (Followers: 6)
Energy Studies Review     Open Access   (Followers: 4)
Energy Systems     Hybrid Journal   (Followers: 10)
Energy Technology     Partially Free   (Followers: 3)
Energy, Sustainability and Society     Open Access   (Followers: 18)
Environmental Progress & Sustainable Energy     Hybrid Journal   (Followers: 4)
EPJ Photovoltaics     Open Access   (Followers: 1)
Facta Universitatis, Series : Electronics and Energetics     Open Access  
Foundations and Trends® in Renewable Energy     Full-text available via subscription   (Followers: 1)
Frontiers in Energy     Hybrid Journal   (Followers: 4)
Frontiers in Energy Research     Open Access   (Followers: 1)
Fuel and Energy Abstracts     Full-text available via subscription   (Followers: 5)
Functional Materials Letters     Hybrid Journal   (Followers: 1)
Gcb Bioenergy     Hybrid Journal   (Followers: 3)
Geothermal Energy     Open Access   (Followers: 1)
GeoWorld     Full-text available via subscription   (Followers: 2)
Green     Full-text available via subscription   (Followers: 2)
IEA Electricity Information     Full-text available via subscription   (Followers: 5)
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: 6)
IEEE Transactions on Nuclear Science     Hybrid Journal   (Followers: 7)
IEEE Transactions on Power Systems     Hybrid Journal   (Followers: 10)
IET Power Electronics     Hybrid Journal   (Followers: 10)
Ingeniería Energética     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: 2)
International Journal of Applied Power Engineering     Open Access   (Followers: 2)
International Journal of Clean Coal and Energy     Open Access   (Followers: 4)
International Journal of Coal Science & Technology     Open Access  
International Journal of Critical Infrastructure Protection     Hybrid Journal   (Followers: 5)
International Journal of Electric and Hybrid Vehicles     Hybrid Journal   (Followers: 5)
International Journal of Emerging Electric Power Systems     Full-text available via subscription   (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 Engineering     Open Access   (Followers: 12)
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: 2)
International Journal of Global Energy Issues     Hybrid Journal   (Followers: 6)
International Journal of Green Energy     Hybrid Journal   (Followers: 6)
International Journal of Hydrogen Energy     Partially Free   (Followers: 12)
International Journal of Marine Energy     Full-text available via subscription   (Followers: 2)
International Journal of Nuclear Desalination     Hybrid Journal   (Followers: 2)
International Journal of Nuclear Energy Science and Technology     Hybrid Journal   (Followers: 2)
International Journal of Nuclear Governance, Economy and Ecology     Hybrid Journal   (Followers: 2)

        1 2 | Last

Journal Cover   Structural Control and Health Monitoring
  [SJR: 1.148]   [H-I: 21]   [7 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1545-2255 - ISSN (Online) 1545-2263
   Published by John Wiley and Sons Homepage  [1606 journals]
  • Damage detection in structures using a transmissibility‐based
           Mahalanobis distance
    • Authors: Yun‐Lai Zhou; E. Figueiredo, N. Maia, R. Sampaio, R. Perera
      Pages: n/a - n/a
      Abstract: In this paper, a damage‐detection approach using the Mahalanobis distance with structural forced dynamic response data, in the form of transmissibility, is proposed. Transmissibility, as a damage‐sensitive feature, varies in accordance with the damage level. Besides, Mahalanobis distance can distinguish the damaged structural state condition from the undamaged one by condensing the baseline data. For comparison reasons, the Mahalanobis distance results using transmissibility are compared with those using frequency response functions. The experiment results reveal quite a significant capacity for damage detection, and the comparison between the use of transmissibility and frequency response functions shows that, in both cases, the different damage scenarios could be well detected. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-27T03:51:56.089969-05:
      DOI: 10.1002/stc.1743
  • Novelty detection for SHM using raw acceleration measurements
    • Authors: Vinicius Alves; Alexandre Cury, Ney Roitman, Carlos Magluta, Christian Cremona
      Pages: n/a - n/a
      Abstract: Structural health monitoring is a problem that can be addressed at many levels. One of the most promising approaches used in damage assessment problems is based on pattern recognition. The idea is to extract features from data that characterize only the normal condition and to use them as a template or reference. During structural monitoring, data are measured, and appropriate features are extracted as well as compared with the reference. Any significant deviations are considered as signal novelty or possible damage. Several studies present in the literature are based on the comparison of measured vibration data such as natural frequencies and vibration modes in undamaged and damaged states of the structure. This methodology has proven to be efficient; however, its application may not be the most adequate in cases where the engineer needs to know with certain imperativeness the condition of a given structure. This paper proposes a novelty detection approach where the concept of symbolic data analysis is used to manipulate raw vibration data (i.e., acceleration measurements). These quantities (transformed into symbolic data) are combined to three unsupervised classification techniques: hierarchy agglomerative, dynamic clouds and soft c‐means clustering. In order to attest the robustness of this approach, experimental tests are performed on a simply supported beam considering different damage scenarios. Moreover, this paper presents a study with tests conducted on a motorway bridge, in France, where thermal variation effects also play a major role. In summary, results obtained confirm the efficiency of the proposed methodology. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-27T02:17:29.907637-05:
      DOI: 10.1002/stc.1741
  • Free vibrations of a two‐cable network with near‐support
           dampers and a cross‐link
    • Authors: Haijun Zhou; Xia Yang, Limin Sun, Feng Xing
      Pages: n/a - n/a
      Abstract: Vibration mitigation of cables is a crucial problem for cable‐supported bridges. A hybrid method for cable vibration mitigation that combines cross‐ties and dampers has been applied in engineering practice; however, the damping and frequency of this kind of system needs to be further assessed. In this paper, a system of two parallel cables with a cross‐link and dampers located near the cable anchorage is proposed and analyzed. Based on displacement continuity and force equilibrium at the damper and spring locations, the characteristic equation of the system is derived by applying the transfer matrix method. The complex characteristic equation is then numerically solved to obtain the modal damping and frequencies. The damping and frequency characteristics are discussed in detail for the case when the two cables are identical. Special attention is given to the case when only one damper is installed, and the approximate damping evaluation formulations are proposed when spring stiffness approaches infinity. Effects of mass–tension ratio, cable length ratio and frequency ratio on damping are also addressed. Finally, a case study of multimode damping optimization for bridge hangers is given. The results of this paper could be useful for vibration mitigation of two parallel cables and further development of design guidelines for cable networks with attached dampers. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-18T02:57:15.196647-05:
      DOI: 10.1002/stc.1738
  • Spatial H∞ approach to damage‐tolerant active control
    • Authors: Nazih Mechbal; Eurípedes G. O. Nóbrega
      Pages: n/a - n/a
      Abstract: Damage‐tolerant active control is a new research area targeting to adapt fault‐tolerant control methods to mechanical structures submitted to damage. Active vibration control is a mature engineering area, using modern control methods to address structural issues that may result from excessive vibration. However, the subject of structural vibration control under damage represents a novel subject in the literature. There are some difficulties to adapt regular controller designs to active control, which may not result in good performance even for healthy structures. Fault detection and diagnosing research has conducted to the development of the fault‐tolerant control area, whose methods are equally hard to translate to damaged structure control. Spatial active vibration control encompasses some techniques that present important features to structure control; however, this is not necessarily true in the general control design area, where spatial constraints are normally not involved. In this paper, we propose an investigation of these spatial techniques, applied to structural damage control. Several new strategies for vibration control are presented and analyzed, aiming to attain specific objectives in damage control of mechanical structures. Finite element models are developed for a case study structure, considering healthy and three different damage conditions, which are used to design controllers, adopting an approach based on an H∞ spatial norm, and according to some of the proposed strategies. Discussion of the achieved results contributes to clarify the main concepts related to this new research area, and controller performance analysis permits to foresee successful real case application of the techniques here described. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-17T03:26:32.088281-05:
      DOI: 10.1002/stc.1729
  • Guided wave propagation in high‐speed train axle and damage
           detection based on wave mode conversion
    • Authors: Fucai Li; Xuewei Sun, Jianxi Qiu, Limin Zhou, Hongguang Li, Guang Meng
      Pages: n/a - n/a
      Abstract: Axle is the main bearing part of the bogie system on a high‐speed train and is therefore requested on a higher reliability level. The high‐speed train axle is thick‐walled hollow cylindrical structure with variable cross section, which complicates ultrasonic guided wave propagation in the structure. Characteristics of the guided wave propagation in the train axle are systematically investigated in this study, so as to explore guided wave‐based structural health monitoring (SHM) method for this kind of structure. Piezoelectric patches are used as actuator to excite waves in the axle. Generated wave signals using single actuator and circumferential, limited number of actuator configurations are compared to optimize the transducer network. The longitudinal wave modes are therefore selected for damage detection of this kind of structure. Based on the analytical and finite element analysis (FEA), when the symmetric longitudinal wave modes meet defect, if have, in the train axle with variable cross section, mode conversion will happen and asymmetric flexural wave modes are therefore generated. Wave mode conversion‐based SHM technique is consequently proposed. The FEA results demonstrate the feasibility of guided wave‐based SHM technique for high‐speed train axle. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-17T01:02:21.826163-05:
      DOI: 10.1002/stc.1739
  • Data compression of very large‐scale structural seismic and typhoon
           responses by low‐rank representation with matrix reshape
    • Authors: Yongchao Yang; Satish Nagarajaiah, Yi‐Qing Ni
      Pages: n/a - n/a
      Abstract: The intrinsic low‐dimensional structure, which is implicit in the large‐scale data sets of structural seismic and typhoon responses, is exploited for efficient data compression. Such a low‐dimensional structure, empirically, stems from few modes that are active in the structural dynamic responses. Originally, limited to the sensor and time‐history dimension, the structural seismic and typhoon response data set generally does not have an explicit low‐rank representation (e.g., by singular value decomposition or principal component analysis), which is critical in multi‐channel data compression. By the proposed matrix reshape scheme, the low‐rank structure of the large‐scale data set stands out, regardless of the original data dimension. Examples demonstrate that the developed method can significantly compress the large‐scale structural seismic and typhoon response data sets, which were recorded by the structural health monitoring system of the super high‐rise Canton Tower. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-17T00:25:57.338843-05:
      DOI: 10.1002/stc.1737
  • Signal‐based nonlinear modelling for damage assessment under
           variable temperature conditions by means of acousto‐ultrasonics
    • Authors: M.‐A. Torres‐Arredondo; Julian Sierra‐Pérez, D.‐A. Tibaduiza, Malcolm McGugan, José Rodellar, C.‐P. Fritzen
      Pages: n/a - n/a
      Abstract: Damage assessment can be considered as the main task within the context of structural health monitoring (SHM) systems. This task is not only confined to the detection of damages in its basic algorithms but also in the generation of early warnings to prevent possible catastrophes in the daily use of the structures ensuring their proper functioning. Changes in environmental and operational conditions (EOC), in particularly temperature, affect the performance of SHM systems that constitutes a great limitation for their implementation in real world applications. This paper describes a health monitoring methodology combining the advantages of guided ultrasonic waves together with the compensation for temperature effects and the extraction of defect‐sensitive features for the purpose of carrying out a nonlinear multivariate diagnosis of damage. Two well‐known methods to compensate the temperature effects, namely optimal baseline selection and optimal signal stretch, are investigated within the proposed methodology where the performance is assessed using receiver operating characteristic curves. The methodology is experimentally tested in a pipeline. Results show that the methodology is a robust practical solution to compensate the temperature effects for the damage detection task. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-10T05:23:58.831046-05:
      DOI: 10.1002/stc.1735
  • Dynamic behavior of adjacent buildings connected by linear
           viscous/viscoelastic dampers
    • Authors: E. Tubaldi
      Pages: n/a - n/a
      Abstract: This paper analyzes the properties of the dynamic behavior of two adjacent buildings of different height connected by viscous/viscoelastic dampers located at the top of the shortest building. The adjacent structures are described through a continuum approach as two interconnected uniform shear beams. This permits to identify the set of characteristic parameters describing the building and damper properties that completely control the dynamic behavior of the system. An analytical solution is derived for solving the eigenvalue problem via complex modal analysis, and a parametric study is carried out to evaluate the influence of these characteristic parameters on the properties of the dynamic system. A reduced‐order model of the system is also developed, and simplified formulas are obtained for estimating the damping ratios of the first two modes of the coupled system. Two case studies consisting of realistic shear‐type adjacent buildings coupled by viscous dampers are finally analyzed. The estimates of the modal properties obtained by using the proposed analytical approach and a finite element formulation are compared with each other. It is shown that the proposed approach provides information useful for the preliminary design of the damper properties ensuring the optimal control against seismic loadings. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-10T05:23:44.865978-05:
      DOI: 10.1002/stc.1734
  • Numerical simulation and analysis of nonlinear state‐space control
           design for hydraulic actuator control
    • Authors: Hadi Moosavi; Reza Mirza Hessabi, Oya Mercan
      Pages: n/a - n/a
      Abstract: In order to investigate the dynamic behavior of complex structural systems experimental testing is indispensable and real‐time pseudodynamic (PSD) and real‐time hybrid simulation (RTHS) are versatile testing methods to address this need. Accurate control of hydraulic actuators is essential for the accuracy and stability of these methods. This paper introduces a nonlinear state‐space controller to control hydraulic actuators under displacement control, specifically for real‐time testing applications. The proposed control design process uses the nonlinear state‐space model of the system, and utilizes state feedback linearization through a transformation of the state variables. As such, it can efficiently handle the nonlinearities associated with the servo‐hydraulic system and the test structure. Comparisons of numerical simulation results for linear state‐space and nonlinear state‐space controllers are provided. The improved tracking performance of the proposed controller will contribute to more accurate real‐time test results, which in turn will enable a more accurate assessment of dynamic characteristics of complex structural systems. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-09T04:01:46.897354-05:
      DOI: 10.1002/stc.1731
  • Investigations on a particle filter algorithm for crack identification in
           beams from vibration measurements
    • Authors: R. Rangaraj; Bharat Pokale, Anuradha Banerjee, Sayan Gupta
      Pages: n/a - n/a
      Abstract: This study focuses on crack identification in beams from vibration measurements using principles of dynamic state estimation. The FEM is used to model the beam with cracked‐beam elements that account for the presence of an edge crack under near‐tip elasto‐plastic conditions. The crack size and its location are treated as the variables that are identified using a particle filter algorithm. A parametric study is first carried out with synthetic measurements to numerically analyze the performance of the algorithm. Subsequently, using measurements acquired from physical experiments involving a cantilever beam subjected to arbitrary excitations, the proposed algorithm is used to identify the size and location of crack‐like defects. The proposed method does not require measurements of the undamaged beam, hence, can be used for crack identification in beams for which no earlier measurements are available. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-03T00:36:25.645131-05:
      DOI: 10.1002/stc.1733
  • Structural identification with incomplete instrumentation and global
           identifiability requirements under base excitation
    • Authors: Suparno Mukhopadhyay; Hilmi Lus, Raimondo Betti
      Pages: n/a - n/a
      Abstract: Estimating the mass and stiffness parameters of a structural system via its vibration response measurements is the primary objective in the field of modal testing and structural health monitoring. The attainment of this objective, however, is hindered by various practical and theoretical issues. One such issue is incomplete instrumentation, leading to spatially incomplete mode shapes and often nonunique identification results. When the excitation is induced by ground motion, the problem is further complicated because of arbitrary normalization of mode shapes. This study attempts to address these issues for shear‐building type structures. Mode shape normalization and expansion approaches are developed that utilize the topology of the structural matrices. Theoretical constraints regarding minimal instrumentation and the necessity for any a priori information are addressed vis‐à‐vis the requirements for global identifiability. Some practical implementation issues are discussed. The performance of the method is evaluated using numerical simulations and shake table experiments. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-02-03T00:29:42.294075-05:
      DOI: 10.1002/stc.1732
  • Issue Information
    • Pages: i - ii
      Abstract: No abstract is available for this article.
      PubDate: 2015-01-27T22:12:52.09327-05:0
      DOI: 10.1002/stc.1693
  • Monitoring horizontal displacements in a vertical profile of a tall
           industrial chimney using Global Positioning System technology for
           detecting dynamic characteristics
    • Authors: Peter Breuer; Tadeusz Chmielewski, Piotr Górski, Eduard Konopka, Lesław Tarczyński
      Pages: n/a - n/a
      Abstract: Global Positioning System (GPS) dual‐frequency receivers installed at three various levels were used in two field tests to record the response of the 300‐m tall industrial chimney, located in the power station of Bełchatów (Poland), exposed to the light wind and temperature variations. The fast Fourier transformation and the peak‐picking approach based on the band‐pass filtering technique (a second‐order Type 1 Chebyshev band‐pass) were employed to detect dominant natural frequencies and relevant vibrations of the maximum displacements of the chimney. The damping ratios for both tests were also determined. The estimated first natural frequencies and mode shapes, using GPS measurements, matched well with predicted from a calculation of the finite element model, created for the chimney. The assessment of measurement errors caused by GPS system before and after filtering is also presented. This paper concludes that GPS is a viable tool for detecting the structural dynamic characteristics and that GPS is capable of tracking the vibrations of long‐period structures to a few millimetres—in our tests to 2 mm during short time intervals. These results were obtained by using the GPS 10 Hz filtered data. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-01-23T03:16:02.571235-05:
      DOI: 10.1002/stc.1730
  • Adaptive HHT (AHHT) based modal parameter estimation from limited
           measurements of an RC‐framed building under multi‐component
           earthquake excitations
    • Authors: Swarup Mahato; Meda Vinay Teja, Arunasis Chakraborty
      Pages: n/a - n/a
      Abstract: Present study aims to develop Hilbert–Huang transformation based signal processing scheme to identify the modal parameters of a reinforced concrete framed building subjected to multi‐component earthquake excitations. An adaptive band‐pass filtering strategy is developed to identify modal parameters (i.e. natural frequencies, damping and mode shapes). The proposed method is unique as it identifies the system parameters from the limited measurements due to arbitrary non‐stationary excitations. The advantage of this technique is its ability to extract a complete set of modal frequencies from each measurement. The mode shapes are identified by updating the finite element model using the estimated modal parameters. In this context, the proposed method is effective as the large number of modal parameters identified from each measurement help to optimize the finite element model. The accuracy of the proposed method is demonstrated using both synthetic and actual measurements during an earthquake. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-01-12T04:02:30.761374-05:
      DOI: 10.1002/stc.1727
  • Identification of material properties – efficient modelling approach
           based on guided wave propagation and spatial multiple signal
    • Authors: L. Ambrozinski; P. Packo, L. Pieczonka, T. Stepinski, T. Uhl, W. J. Staszewski
      Pages: n/a - n/a
      Abstract: Modern structures are often designed using new types of lightweight materials of interesting properties. Accurate information on physical properties of these materials is a key element of every stage of lifecycle from design through maintenance to retirement. Although there are numerous experimental methods that can be used for material testing, only a small handful of these methods provide required information on material parameters in a nondestructive and in‐operational manner, assuring high level of accuracy. The paper demonstrates application of a method that can be used to estimate material properties of engineering structures. The method is based on guided wave propagation and dispersion characteristics. The proposed approach combines three recently developed elements, that is, efficient numerical, experimental and image processing analyses: (i) wave propagation modelling is based on two finite difference approaches, that is, the semianalytical finite difference method and the 3‐D local interaction simulation approach implemented with a multigeneral‐purpose computing on graphics processing units platform to avoid numerical discrepancies and to reduce the computational effort; (ii) experimental testing utilises noncontact, scanning laser vibrometry; and (iii) image processing involves spatial multiple signal classification to improve dispersion curve estimation. This unique combination offers a reliable approach for material parameter estimation. The proposed method is fully nondestructive and can be performed online under varying operational conditions. The method is demonstrated using Young's modulus estimation of an aluminium plate. The results are compared using the traditional destructive approach based on a three‐point bending test. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-01-07T01:42:59.292331-05:
      DOI: 10.1002/stc.1728
  • Modelling the degradation of vibration characteristics of reinforced
           concrete beams due to flexural damage
    • Authors: W. I. Hamad; J. S. Owen, M. F. M. Hussein
      Pages: n/a - n/a
      Abstract: This paper presents an improved crack model incorporating non‐linearity of flexural damage in concrete to reproduce changes in vibration properties of cracked reinforced concrete beams. A reinforced concrete beam model with multiple‐distributed flexural cracks is developed, in which the cracked regions are modelled using the fictitious crack approach and the undamaged parts are treated in a linear‐elastic manner. The model is subject to incremental static four‐point bending, and its dynamic behaviour is examined using different sinusoidal excitations including swept sine and harmonic signals. From the swept sine excitations, the model simulates changes in resonant frequency with increasing damage. The harmonic excitations are utilised to investigate changes in modal stiffness extracted from the restoring force surfaces, and changes in the level of non‐linearity are deduced from the appearance of super‐harmonics in the frequency domain. The simulation results are compared with experimental data of reinforced concrete beams subject to incremental static four‐point bending. The comparisons revealed that the proposed crack model is able to quantitatively predict changes in vibration characteristics of cracked reinforced concrete beams. Changes are sensitive to support stiffness, where the sensitivity increases with stiffer support conditions. Changes in the level of non‐linearity with damage are not suitable for damage detection in reinforced concrete structures because they do not follow a monotonic trend. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-12-04T04:47:09.072598-05:
      DOI: 10.1002/stc.1726
  • Optimum design of tuned mass damper floor system integrated into
           bending‐shear type building based on H∞, H2, and stability
           maximization criteria
    • Authors: Ping Xiang; Akira Nishitani
      Pages: n/a - n/a
      Abstract: A new vibration control system integrating multiple tuned mass damper (TMD) floors into building structures was recently proposed by the authors, which has been demonstrated to be highly effective in mitigating both interstory drifts and floor accelerations for low‐rise and medium‐rise buildings. Actually, this system is attracting especially for tall buildings, which may not be suitable for base isolation because large tensile forces exert on them. This paper aims to investigate the control effect of the proposed TMD floor system for high‐rise buildings that are represented as bending‐shear type models. An optimum design criterion integrating stability maximization criterion is developed for such a multi‐degree‐of‐freedom TMD floor integrated high‐rise building system. Additionally, a multi‐objective optimization genetic algorithm Nondominated Sorting Genetic Algorithm II is employed to solve the multi‐objective optimization problem with the combination of the stability maximization criterion and H∞ or H2 criterion. Two series of numerical simulations, that is, the cases in which all the floors serve as TMDs and only a limited number of floors serve as TMDs, are conducted. The favorable performance of the proposed TMD floor system for high‐rise buildings is demonstrated by comparisons with a fixed floor building equipped with additional high‐damping devices achieving 10% first modal damping ratio under a various of seismic excitations. The TMD floor system is verified to have satisfying control effect, which can also solve the post‐earthquake long‐duration vibration problem of high‐rise buildings observed in the 2011 great Tohoku earthquake. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-12-01T01:44:17.912463-05:
      DOI: 10.1002/stc.1725
  • Application of support vector machine for pattern classification of active
           thermometry‐based pipeline scour monitoring
    • Authors: Xuefeng Zhao; Weijie Li, Lei Zhou, Gangbing Song, Qin Ba, Siu Chun Michael Ho, Jinping Ou
      Pages: n/a - n/a
      Abstract: Pipeline scour monitoring is becoming one of the key requirements in oil and gas industry. To implement scour monitoring for offshore pipeline, a monitoring system that based on active thermometry is proposed. Our previous investigations have shown that the system has provided many advantages over traditional scour monitoring methods. In this paper, a novel scour automatic detection scheme based on nonlinear curve fitting and support vector machine (SVM) is proposed to realize automatic diagnosis of pipeline scour. On account of the varied heat transfer patterns of a line heat source in sediment and water scenarios, the experimental temperature profiles are nonlinearly fitted to their theoretical models. Features extracted by nonlinear curve fitting can dramatically reduce the dimensions of the data. Subsequently, the extracted features are inputted into SVM classifier to judge where the pipeline is exposed to water or buried in the sediment. In order to evaluate the performance of SVM, SVM with different kernel functions are compared with the back‐propagation neural networks, which is the most popular neural network for pattern recognition and classification. Results show that the SVM model with radial basis function kernel outperformed other classification models. Finally, aiming to obtain the optimal heating time of the system, the optimal SVM model is employed to recognize datasets with different heating time. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-12-01T01:43:20.867919-05:
      DOI: 10.1002/stc.1724
  • Structural damage diagnosis using frequency response functions and
           orthogonal matching pursuit: theoretical development
    • Authors: Ryan J. Link; David C. Zimmerman
      Pages: n/a - n/a
      Abstract: A structural damage diagnosis procedure that directly uses the frequency response function is developed. Frequency response data from a possibly damaged system and a finite element model of the healthy system are used to form a damage residual—a mathematical proxy or signature of structural damage. This damage residual can be calculated in the presence of incomplete measurements and at multiple frequencies. A system of equations is then formed, which relates the damage residual to the actual damage on each element represented as a fractional stiffness loss. Therefore, only damage affecting the stiffness properties of the structure is considered here. Classical dynamic model condensation is used in the formation of these equations to overcome the coordinate mismatch created by the incomplete measurement problem. The system of equations created using the damage residual is usually overdetermined and subject to noise, error as a result of the model reduction, and general ill‐conditioning. To overcome these issues, a method known as orthogonal matching pursuit is used to solve the equations for the percent damage. Orthogonal matching pursuit is a method of sparse recovery that solves for the damage in terms of the fewest number of elements. Simulation studies are performed on a truss structure. The damage diagnosis method is shown to accurately identify multiple damage cases. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-12-01T01:39:38.502491-05:
      DOI: 10.1002/stc.1720
  • Acoustic emission monitoring of early corrosion in prestressed concrete
    • Authors: William Vélez; Fabio Matta, Paul Ziehl
      Pages: n/a - n/a
      Abstract: Prestressed concrete (PC) piles in marine environments are vulnerable to corrosion damage especially at their tidal zone because of the concurrent exposure of steel reinforcement to moisture, chlorides, and oxygen. Early detection of corrosion in prestressed strands is desirable to enable the effective planning and prioritizing of maintenance operations. This paper reports on experiments aimed at testing the hypothesis that acoustic emission (AE) monitoring is suitable to recognize and classify early corrosion damage in PC piles exposed to saltwater. In fact, AE is sensitive to the formation and growth of microcracks in both steel and concrete, which may develop upon depassivation of reinforcement and buildup of corrosion by‐products. In addition, the influence of AE signals produced through flexural cracks in the concrete is of less concern for PC piles as such cracks are seldom produced under service loads. Five specimens representative of full‐scale portions of PC piles were designed to accelerate corrosion and subjected for 1 year to wet/dry cycles in saltwater simulating tidal action. The specimens were monitored continuously with AE sensors. Benchmark electrochemical measurements were routinely performed to understand when depassivation of the steel strands occurred. Visual evidence of early corrosion was collected from strands removed from two decommissioned specimens. It is shown that AE intensity analysis is more effective than AE signal strength and cumulative signal strength analysis in recognizing corrosion damage. Intensity analysis‐based criteria for the assessment of early corrosion damage are proposed, complementing previously developed criteria for more severe corrosion damage in steel strands. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-11-26T07:06:10.445504-05:
      DOI: 10.1002/stc.1723
  • Output‐only observer/Kalman filter identification (O3KID)
    • Authors: Francesco Vicario; Minh Q. Phan, Raimondo Betti, Richard W. Longman
      Pages: n/a - n/a
      Abstract: This paper presents output‐only observer/Kalman filter identification (O3KID), an effective method for the identification of the dynamic model of a structure and its underlying modal parameters using only output time histories measured on the field. The method is suitable for structural health monitoring based on modal parameters, in particular, for those civil infrastructures whose excitation is random in nature and in the way that it is applied to the structure (e.g., wind and traffic) and therefore is difficult to measure. O3KID is based on a linear‐time‐invariant state‐space model and is derived from an established and successful approach for input–output system identification, known as observer/Kalman filter identification. The paper rigorously proves the applicability of the approach to the output‐only case, presents the resulting new algorithms, and demonstrates them via examples on both numerical and experimental data. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-11-21T03:17:09.104756-05:
      DOI: 10.1002/stc.1719
  • Optimal control for vibration peak reduction via minimizing large
    • Authors: Zu‐Guang Ying; Yi‐Qing Q. Ni
      Pages: n/a - n/a
      Abstract: An optimal control method for peak response reduction and its application to a tall building structure for reducing peak earthquake responses are presented in this paper. A critical value is used for magnifying large responses and performance index. A structural control system is transformed, and the dynamical programming principle is applied to form a dynamical programming equation. For a certain higher‐order power function in the index, a nonlinear optimal control law with the corresponding Riccati equation is obtained for minimizing structural large responses or peak responses. The asymptotic stability of the autonomous controlled system is proved by using the Lyapunov method. Then the proposed control method is applied to a single degree‐of‐freedom system and a 51‐storey building structure with active mass damper on the top floor under earthquake excitation. Numerical results on peak displacements, interstorey drifts, accelerations and controls are given to illustrate the high control effectiveness of the proposed control method for peak response reduction. The proposed control method has a simple and convenient procedure for multi‐degree‐of‐freedom structures. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-11-19T03:11:50.071542-05:
      DOI: 10.1002/stc.1722
  • Drive‐by damage detection in bridges using the apparent profile
    • Authors: E. J. OBrien; J. Keenahan
      Pages: n/a - n/a
      Abstract: The concept of using sensors on a passing vehicle, rather than on the bridge, is known as 'Drive‐by' damage detection. The newly developed traffic speed deflectometer (TSD) is a device used for pavement deflection measurements and is investigated here in numerical simulations as a means of bridge damage detection. A TSD vehicle model containing two displacement sensors is simulated crossing a simply supported finite element beam containing damage simulated as a loss in stiffness of one of the elements. An adapted Cross Entropy optimisation algorithm procedure is proposed to determine the apparent profile, where the displacements recorded by the sensors are used as the inputs. The time‐shifted difference in the apparent profile is used as the damage indicator. Results show that this can be reliably used as a damage indicator in the presence of noise and changes in the transverse position of the vehicle on the bridge. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-11-14T03:28:26.701078-05:
      DOI: 10.1002/stc.1721
  • Experimental study of pipeline leak detection based on hoop strain
    • Authors: Zi‐guang Jia; Liang Ren, Hong‐nan Li, Siu‐Chun Ho, Gang‐bing Song
      Pages: n/a - n/a
      Abstract: Pipelines are widely used for the transport of a large variety of fluids, such as natural gas, across long distances. While pipelines provide a convenient mode of transportation of fluids, their safe usage is one of the foremost concerns especially if their contents are harmful to the environment or if the hosting area is prone to third‐party intrusions. Thus, rapid detection and localization of pipeline leakage is paramount to the minimization of damage brought to the environment and stakeholders in the event of an unexpected leakage. In this work, a novel hoop strain based negative pressure wave (NPW) approach was used to detect and localize pipeline leakages in a 180 ft PVC pipeline equipped with five manually controllable leakage points. Using the new approach, both the arrival time of the NPW and the energy attenuation profile of the NPW can be used to detect and localize leakages with higher accuracy and in a wider variety of situations. The time of arrival approach allowed accurate (within 7.33% error) and repeatable localization of the leakage points; however, using the energy attenuation of the NPW, leakages with low leakage rates (
      PubDate: 2014-11-14T03:26:01.307815-05:
      DOI: 10.1002/stc.1718
  • Seismic performance assessment of steel frames equipped with a novel
           passive damper using a new damper performance index
    • Authors: Saeed Mahjoubi; Shervin Maleki
      Pages: n/a - n/a
      Abstract: Seismic response of steel moment‐resisting frames equipped with a novel passive damper called infilled‐pipe damper (IPD) is investigated in this study. The IPD is a very economical and easily assembled structural control device with high energy absorption, invented recently by the authors. A simplified trilinear load–displacement model for IPD devices is suggested to be used in this study and further investigations. Next, criteria for IPD elements size selection are proposed for passive control of structures against earthquake loads. Steel frame structures of 5, 10, and 20 stories are designed without any IPD devices. Then, the frames are equipped with IPDs of different stiffness. The frames are subjected to seven earthquake excitations scaled to design basis earthquake and maximum considered earthquake levels. Several response parameters including energy segments and normalized energy ratios are considered, and the performance of the IPDs in reducing each response is evaluated. A new damper performance index, considering global structural damage, local destructive damage and nonstructural damage in a single relationship, is suggested in this study. The index can be employed for optimization purposes in structures equipped with different types of dampers. The results show that the IPD devices dissipate a considerable portion of the seismic input energy and reduce the structural and nonstructural damages. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-11-06T22:01:50.095733-05:
      DOI: 10.1002/stc.1717
  • Hybrid active tuned mass dampers for structures under the ground
    • Authors: Chunxiang Li; Baoya Cao
      Pages: n/a - n/a
      Abstract: The hybrid active tuned mass dampers (HATMD)—a new control system—have been proposed to attenuate undesirable oscillations of structures under the ground acceleration. Based on the authors recent exploration, the performance of the active tuned mass damper (ATMD) with the negative normalized acceleration feedback gain factors (NNAFGF) scheme is better than that with the positive NAFGF (PNAFGF) scheme; therefore, the active control forces of the HATMD are generated by combined use of both the NNAFGF and PNAFGF schemes. In the light of the mode‐generalized system in the specific vibration mode being controlled (simply referred here to as the structure) and accordingly deduced formulae, the expression then is defined for the dynamic magnification factor (DMF) of the structure furnished with the HATMD. Naturally, the criterion for the optimum searching can be determined as the minimization of the minimum values of the maximum DMF. By resorting to the selected criterion and utilizing a genetic algorithm, the effects of varying the key parameters on the optimum performance of the HATMD have been scrutinized both to arrive at the parameter combinations that make it best work and to make an attempt to shed light on the particular phenomena that for it there may exist. Furthermore, for the purpose of comparison, this study simultaneously investigates the optimum performance of both the ATMD and active–passive tuned mass dampers (APTMD) employing the proposed NNAFGF scheme. It is found in terms of numerical results that the HATMD outperforms both the ATMD and APTMD. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-11-06T21:45:17.7776-05:00
      DOI: 10.1002/stc.1716
  • The influence of damping on floor spectra in seismic isolated nuclear
    • Authors: James M. Kelly; Maria Rosaria Marsico
      Pages: n/a - n/a
      Abstract: Seismic isolation is now being considered for nuclear power plant structures and has been applied to many nuclear structures including reactor buildings in France. A draft report entitled ‘Technical Considerations for Seismic Isolation Nuclear Facilities’ has been prepared by the USA Nuclear Regulatory Commission in 2010. It sets out to describe different types of isolators and recommends that lead plug isolators and FP isolators are acceptable choices for nuclear isolation systems. For the design of base isolation systems for nuclear structures, the design engineer is faced with very large design displacements for the isolators and supplementary dampers or highly damped isolators are prescribed to reduce them. These dampers reduce displacements but at the expense of significant increases in interstory drifts and floor accelerations in the superstructure. In this paper, an elementary analysis based on a simple model of an isolated structure is used to demonstrate this dilemma. The model is linear and is based on modal analysis, but includes the modal coupling terms caused by high levels of damping in the isolation system. Estimates of the floor response quantities are obtained by the response spectrum method. It is shown that as the damping in the isolation system increases, the contribution of the modal coupling terms becomes the dominant term. The results show that the use of damping in seismic isolation when the purpose of the isolators is to protect sensitive internal equipment is a misplaced effort, and alternative strategies to solve the problem are suggested. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-10-22T22:57:48.158065-05:
      DOI: 10.1002/stc.1715
  • Development and application of a relative displacement sensor for
           structural health monitoring of composite bridges
    • Authors: Jun Li; Hong Hao, Keqing Fan, James Brownjohn
      Pages: n/a - n/a
      Abstract: This paper proposes a relative displacement sensor developed to measure directly the relative slip between slab and girder in composite bridges for assessing the health condition of shear connections. The structure, design principle, features, and calibration of the developed relative displacement sensor are presented. The design of the sensor ensures that there are no voltage outputs for the tension, compression, bending, and torsion effects, but only for the relative displacement between the two connecting pads of the sensor. The accuracy of the developed sensor in measuring the relative displacement response and using it for monitoring the conditions of shear connectors was tested on a composite bridge model in the laboratory. Shear connection condition was monitored under ambient vibrations, then static load tests were conducted to introduce cracks into the composite bridge. Both the vertical deflections and relative displacements were used for the crack detection. Experimental studies demonstrate that the developed sensor is very sensitive to the relative displacement and has a decent performance for the structural health monitoring of composite bridges. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-10-21T03:39:13.324371-05:
      DOI: 10.1002/stc.1714
  • Optimum tuning of Tuned Mass Dampers for frame structures under earthquake
    • Authors: Jonathan Salvi; Egidio Rizzi
      Pages: n/a - n/a
      Abstract: Tuned Mass Damper (TMD) devices are one of the oldest vibration control means and are widely used in different engineering contexts. Despite the bulk of literature on various TMD‐related issues, the effectiveness of TMDs in reducing the earthquake response of civil engineering structures is still debated. This paper deals with the optimum tuning of the free parameters of a passive TMD applied to sample frame structures subjected to selected seismic excitations. A tuning procedure consisting of a numerical Minimax optimization algorithm is implemented within MATLAB. The so‐conceived TMD turns out to be optimum with respect to the specific seismic event, hence allowing for optimum reduction in primary seismic response. Both optimization process and seismic analysis are carried out in the time domain, through direct integration of the equations of motion. The method is tested on benchmark single‐DOF and multi‐DOF shear‐type prototype structures from the literature by assuming first the Imperial Valley 1940 seismic input, as a sort of benchmark excitation, and then additional recent strong motion earthquakes. In essence, this paper shows that, in principle, with present reference to frame structures, the optimum tuning of TMD parameters at given seismic input is theoretically possible. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-10-20T00:59:38.172266-05:
      DOI: 10.1002/stc.1710
  • An algorithm based on two‐step Kalman filter for intelligent
           structural damage detection
    • Authors: Ying Lei; Feng Chen, Huan Zhou
      Pages: n/a - n/a
      Abstract: In the traditional extended Kalman filter approach, unknown structural parameters are included in the extended state vector. Then, the sizes of the extended state vector and the corresponding state equation are quite large, and the state equation is highly nonlinear with respect to the extended state vector. This may cause identification divergent for a large number of unknown parameters. Also, such strategy requires large computational effort and storage capacities, which is not appropriate for intelligent structural damage detection implemented by smart sensors with microprocessors. In this paper, an algorithm based on a two‐step Kalman filter approach is proposed to remove the aforementioned drawbacks of the traditional extended Kalman filter. In the first step, recursive estimation of structural state vector is derived by Kalman filter with assumed structural parameters. In the second step, structural parameters and the updated structural state vector are estimated by the Kalman filter and the recursive estimation in the first step. Thus, the number of estimated variables in each step is reduced, which reduces the computational effort and storage requirements. This superiority is important for intelligent structural damage detection implemented by smart sensor in wireless sensor network. The proposed algorithm is first validated by numerical simulations results of structural damage detection of the phase‐I 3‐D ASCE benchmark building for structural health monitoring, a 30‐story shear building with minor damage, and an experimental test of damage detection of a lab multistory frame model. Then, it is applied to structural damage detection of a lab multistory model‐employed smart sensors embedded with the proposed algorithm. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-10-17T04:34:36.30652-05:0
      DOI: 10.1002/stc.1712
  • A pseudo local flexibility method for damage detection in hyperstatic
    • Authors: Ting‐Yu Hsu; Wen‐I Liao, Shen‐Yuan Shiao
      Pages: n/a - n/a
      Abstract: Vibration‐based damage detection methods make use of structural features extracted from vibration signals to perform damage diagnosis. The local flexibility method, which can determine local stiffness variations of beam structures by using measured modal parameters, is one of the more promising vibration‐based approaches. The local flexibility method is founded on ‘local’ virtual forces that cause nonzero stresses within a local part of the structure. In this study, this basic rule has been broken. The ‘pseudo‐local’ virtual forces that cause concentrated stresses in a local part and nonzero stresses in the other parts of a structure are employed. The theoretical basis of the proposed ‘pseudo local flexibility method’ (PLFM) is derived. The effects of the number of modes on the damage detection results are studied using both numerical and experimental hyperstatic beam models. The results show that significantly fewer modes are required for the PLFM to estimate the damage location and extent with acceptable accuracy. Therefore, the feasibility of the PLFM is higher because only a limited number of high‐quality modes can be identified in real world applications. Furthermore, it was also found that when damage occurs close to the support, the PLFM is more likely to detect it, which is credited to the smaller local region induced by the PLFM. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-10-15T23:44:56.646246-05:
      DOI: 10.1002/stc.1713
  • Optimal sensor placement for health monitoring of high‐rise
           structure using adaptive monkey algorithm
    • Authors: Ting‐Hua Yi; Hong‐Nan Li, Gangbing Song, Xu‐Dong Zhang
      Pages: n/a - n/a
      Abstract: Optimal sensor placement is a challenging task in the design of an effective structural health monitoring system. In this paper, a novel optimal sensor placement algorithm, called adaptive monkey algorithm (AMA), to cope with the sensor placement problem for target location under constraints of the computing efficiency and convergence stability is proposed. The dual‐structure coding method, instead of the traditional coding method, is adopted to code the solution. The adaptive operator is designed and implemented in the AMA, which provides an automatic technique for adjusting the climb process and watch–jump process of the monkey algorithm according to the observed performance while the search is ongoing. Two new somersault processes, i.e., reflection somersault process and mutation somersault process, are incorporated in the AMA to strengthen its global search ability. Numerical experiments involving two high‐rise structures have been carried out to evaluate the performance of the proposed AMA algorithm. The results demonstrated that the innovations in the AMA make it outperform the other algorithms in most cases in terms of less iterations and generating more stable optimal solutions. This algorithm can also be easily applied to other discrete optimization problems. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-10-15T06:03:56.365396-05:
      DOI: 10.1002/stc.1708
  • Energy‐aware wireless sensor placement in structural health
           monitoring using hybrid discrete firefly algorithm
    • Authors: Guang‐Dong Zhou; Ting‐Hua Yi, Huan Zhang, Hong‐Nan Li
      Pages: n/a - n/a
      Abstract: The extensive utilization of wireless sensor networks (WSNs) in SHM systems promotes optimal wireless sensor placement (OWSP) as an important topic. In this paper, the theoretical framework of OWSP in SHM is presented. Within the framework, the energy‐aware wireless sensor placement is formulated as a discrete optimization problem in which the linear independence of identified mode shapes is achieved, the connectivity of the WSN is guaranteed, and the energy efficiency of an entire WSN is pursued. A hybrid discrete firefly algorithm (HDFA) is developed to solve this complex optimization problem. The one‐dimensional binary coding system and the Hamming distance are adopted to characterize the fireflies so that the distinguished optimization mechanism in the basic FA can be applied to the OWSP problem. A hybrid movement scheme including directive movement and nondirective movement is proposed to improve the convergence speed, enhance the capability of searching global optimization, and avoid falling into the local optimum. The HDFA is applied to a long‐span suspension bridge for verifications, and two other optimization methods, a simple discrete FA and a simple genetic algorithm, are also employed for facilitating comparisons. The results demonstrate that the HDFA can extract an optimal wireless sensor configuration with highly linear independence of identified mode shapes and outstanding WSN performance. And the combination of directive movement and nondirective movement proves that the HDFA can outperform the simple discrete FA and the simple genetic algorithm in terms of computational efficiency and superiority of results. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-10-15T06:01:16.24135-05:0
      DOI: 10.1002/stc.1707
  • Influence of isolation hysteresis on the seismic performance of isolated
    • Authors: Xi Chen; T. Y. Yang, Weixing Shi
      Pages: n/a - n/a
      Abstract: Seismic isolation is one of the most used protective technologies for earthquake engineering. Many innovative devices have been researched and implemented. Selection of the different isolation devices is commonly based on engineering experience, where no detailed and systematic comparison has been provided. In this paper, the seismic performances of a three‐story office building isolated using five different devices were evaluated. The isolation devices included the bilinear, flag‐shaped I, flag‐shaped II, crystallizing rubber (CR), and rigid‐perfectly plastic (RPP) models. These isolation devices were designed to achieve an equivalent performance at the seismic shaking intensity of 2% probability of exceedance in 50 years. The evaluation was conducted using the state‐of‐the‐art assessment procedure at 2%, 10%, and 50% probability of exceedance in 50 years (50/50, 10/50, and 2/50) hazard levels. The results indicated that all the isolators performed well by limiting the financial losses. At both the 50/50 and 10/50 shaking intensities, the building with CR isolators experienced no repair costs, while those with bilinear, flag‐shaped I, flag‐shaped II, and RPP isolators had minor repair costs contributed from the content performance groups. At the 2/50 shaking intensity, all isolators incurred minor damages in the content performance groups. The building with CR isolators had additional repair costs because of the interior drift sensitive nonstructural components, while the building with the RPP isolators had repair costs contributed from the interior drift and acceleration sensitive nonstructural components and the acceleration sensitive equipment at the roof. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-10-10T08:22:06.5617-05:00
      DOI: 10.1002/stc.1709
  • Using a limited set of MR dampers for improving structural seismic
    • Authors: Yuri Ribakov; Grigoriy Agranovich
      Pages: n/a - n/a
      Abstract: Control is one of the methods used for reducing structural response to earthquakes. Optimal active control algorithms allow calculating the forces that should be applied by supplemental devices in order to yield desired structural behavior during an earthquake. However, active devices require large amounts of external power, which are not always available in the real time. Therefore, more economical semiactive devices, combining the best features of passive and active control systems, are used for protecting structures against earthquakes. This study is aimed at finding a simple and effective method for optimal control of structures using magnetorheological dampers. An algorithm for finding effective dampers' locations is used. Additionally, high‐efficiency amplifiers are used for connecting the dampers while decreasing the number of damping units. The location of dampers is found by simulating the structural response to a white noise ground motion. A number of equivalent damping units with amplifiers are obtained assuming equal energy dissipation at minimum amplifying ratio. The effectiveness and performance of the proposed method are further demonstrated by simulating the response of the structure to natural earthquake records. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-10-06T22:54:54.973848-05:
      DOI: 10.1002/stc.1711
  • Ambient modal identification using multi‐rank parallel factor
    • Authors: A. Sadhu; A. Goldack, S. Narasimhan
      Pages: n/a - n/a
      Abstract: In this paper, the problem of underdetermined modal identification where the number of modes to be identified is larger than the available sensor measurements is addressed using parallel factor decomposition and blind source separation. Underdetermined situations not only arise when the number of sensors are limited but also when narrowband excitations are present in the measurements, for example, in pedestrian‐induced vibration of footbridges. The basic premise of the proposed algorithm is based on multiple‐rank parallel factor decomposition of covariance tensors constituted from vibration response measurements. Unlike conventional parallel factor decomposition using a single rank order, the proposed method utilizes multiple rank order decompositions. A stability chart constructed from identified sources through such multiple rank orders allows for the robust estimation of active modes. The statistical characteristics of the resulting modes are evaluated in order to delineate the sources corresponding to external disturbances versus inherent modes of the system. The proposed framework enables an automated selection of rank order, detection of external harmonics and an estimation of modal parameters that are relatively insensitive to the sensor configuration. The performance of the algorithm is illustrated using both numerical studies and an experimental study using pedestrian‐induced vibration measurements of a stress‐ribbon bridge located at the Technical University—Berlin, Germany. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-09-29T00:17:33.542077-05:
      DOI: 10.1002/stc.1706
  • On the observability and identifiability of nonlinear structural and
           mechanical systems
    • Authors: Manolis N. Chatzis; Eleni N. Chatzi, Andrew W. Smyth
      Pages: n/a - n/a
      Abstract: The question of a priori observability of a dynamic system, that is, whether the states of a system can be identified given a particular set of measured quantities is of utmost importance in multiple disciplines including biology, economics, and engineering. More often than not, some of the parameters of the system need to be identified, and thus the issue of identifiability, that is, whether the measurements result in unique or finite solutions for the values of the parameters, is of interest. Identifiability arises in conjunction with the question of observability, when the notion of states may be augmented to include both the actual state variables of the dynamic system and its parameters. This results in the formulation of a nonlinear augmented system even though the dynamic equations of motion of the original system might be linear. In this work, three methods for the observability and identifiability of nonlinear dynamic systems are considered. More specifically, for a system whose state and measurement equations are analytic, the geometric Observability Rank Condition, which is based on Lie derivatives may be used. If the equations are rational, algebraic methods are also available. These include the algebraic observability methods and the algebraic identifiability algorithms which determine the finiteness or uniqueness of the solutions for the parameters. The aforementioned methods are used to study the observability and identifiability of suitable problems in civil engineering and highlight the connections between them and the corresponding concepts. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-09-17T23:01:54.706299-05:
      DOI: 10.1002/stc.1690
  • Robust statistical damage localization with stochastic load vectors
    • Authors: Luciano Marin; Michael Döhler, Dionisio Bernal, Laurent Mevel
      Pages: n/a - n/a
      Abstract: The stochastic dynamic damage locating vector approach is a vibration‐based damage localization method based on a finite element model of a structure and output‐only measurements in both reference and damaged states. A stress field is computed for loads in the null space of a surrogate of the change in the transfer matrix at the sensor positions for some values in the Laplace domain. Then, the damage location is related to positions where the stress is close to zero. Robustness of the localization information can be achieved by aggregating results at different values in the Laplace domain. So far, this approach, and in particular the aggregation, is deterministic and does not take the uncertainty in the stress estimates into account. In this paper, the damage localization method is extended with a statistical framework. The uncertainty in the output‐only measurements is propagated to the stress estimates at different values of the Laplace variable, and these estimates are aggregated based on statistical principles. The performance of the new statistical approach is demonstrated both in a numerical application and a lab experiment, showing a significant improvement of the robustness of the method due to the statistical evaluation of the localization information. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-09-07T22:12:15.155237-05:
      DOI: 10.1002/stc.1686
  • Real‐time hybrid simulations vs shaking table tests: Case study of a
           fibre‐reinforced bearings isolated building under seismic loading
    • Authors: Andrea Calabrese; Salvatore Strano, Mario Terzo
      Pages: n/a - n/a
      Abstract: In this paper, real‐time hybrid simulations (RTHSs) and shaking table tests (STTs) are described to assess the feasibility of using recycled rubber fibre‐reinforced bearings (FRBs) as base isolators of low‐cost buildings in developing countries. The RTHSs were run to predict the behaviour of a prototype‐scaled building under dynamic loading prior to carrying out STTs on the same structural model. Real‐time tests addressed a lack of knowledge regarding the seismic behaviour of FRBs as isolators for low‐rise buildings. They also underlined the feasibility of the shaking table experimental tests and addressed all the safety concerns. In this work, the outcomes of the two different testing procedures were compared. As result, the need to adopt STTs to validate base isolation technologies is questioned and, from the comparison, the advantages and limits of the two testing procedures are presented. Moreover, the acquired knowledge on the dynamic behaviour of recycled rubber bearings validates their use as isolators for seismic risk mitigation in earthquake‐prone regions of the world. Briefly, the objectives of this work can be listed as follows: (i) to provide validation of a newly constructed RTHS testing apparatus at the Department of Industrial Engineering of the University of Naples Federico II, Italy, (ii) to evaluate the effectiveness of recycled rubber FRBs as a low‐cost base isolation system for low‐rise structures against severe seismic events through dynamic testing and (iii) to compare, through tests on the same physical component, the RTHS and shaking table testing techniques. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-09-01T02:15:08.540574-05:
      DOI: 10.1002/stc.1687
  • Dynamic and numerical issues relating to the control robustness of
           dynamically substructured systems
    • Authors: Jia‐Ying Tu; Chih‐Ying Chen, Wei‐De Hsiao
      Pages: n/a - n/a
      Abstract: Dynamically substructured system (DSS) techniques separate critical components of a complete structural system to be physically tested in full size; the remaining linear subsystems are tested numerically. Successful and robust DSS tests rely on a high‐quality controller to cope with undesired disturbances surrounding the real‐time environment and thus ensure synchronised responses of the numerical and physical substructure outputs. Three DSS control systems are compared in this paper, which use dynamics‐based ordinary differential equations or geometry‐based delay differential equations to model the systems. Even though the control designs are not new, a series of new experimental and analytical results capture the essence of DSS control problems in a simple way, showing that (i) reliable DSS tests depend on well‐defined dynamics and numerical computational accuracy in the control design, (ii) dynamics‐based methods lay a relatively transparent and systematic foundation for deeper investigation into robustness issues and (iii) an understanding of potential and fundamental real‐time difficulties is important in order to give hints for accurate modelling, control redesign and quality improvement. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-08-25T01:41:11.044341-05:
      DOI: 10.1002/stc.1685
  • Tuned liquid column dampers for mitigation of edgewise vibrations in
           rotating wind turbine blades
    • Authors: Zili Zhang; Biswajit Basu, Søren R. K. Nielsen
      Pages: n/a - n/a
      Abstract: Edgewise vibrations in wind turbine blades are lightly damped, and large amplitude vibrations induced by the turbulence may significantly shorten the fatigue life of the blade. This paper investigates the performance of tuned liquid column dampers (TLCDs) for mitigating edgewise vibrations in rotating wind turbine blades. Normally, the centrifugal acceleration at the outboard portion of a rotating blade can reach to a magnitude of 7–8 g, which makes it possible to use a TLCD with a very small mass for suppressing edgewise vibrations effectively. The parameters of the TLCD to be optimized are the mounting position, the mass ratio, the geometries, and the head loss coefficient of the damper. Based on a reduced 2‐DOF nonlinear model developed by the authors, the optimization of these parameters are carried out by minimizing the standard deviation of the edgewise tip displacement, with the consideration of both the space limitation inside the blade and the constraint of the liquid motion. The edgewise modal load for the 2‐DOF model has been calculated from a more sophisticated 13‐DOF aeroelastic wind turbine model, which includes the coupling of the blade‐tower‐drivetrain vibration and the aerodynamic damping presented in different modes. Various turbulence intensities and rotational speeds of the rotor have been considered to evaluate the performance of the TLCD. Further, the optimized damper is incorporated into the 13‐DOF model to verify the application of the decoupled optimization. The investigation shows promising results for the use of the TLCD in mitigating edgewise vibrations in wind turbine blades. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-08-24T23:27:05.684623-05:
      DOI: 10.1002/stc.1689
  • A methodology for the integrated seismic design of nonlinear buildings
           with supplemental damping
    • Authors: Oren Lavan
      Pages: n/a - n/a
      Abstract: Designing structures to behave nonlinearly (elastically or inelastically) under strong seismic events has been long recognized to help reducing the seismic forces acting on them. Nonetheless, nonlinear structures often experience larger displacements than their linear counterparts. The concept of allowing nonlinear behavior in structures while capping forces at lower levels and adding viscous damping has been shown to be able to lead to good designs in terms of both levels of seismic forces and peak deformations. This paper presents an approach for the design of nonlinear (elastic or inelastic) structures equipped with viscous dampers that would produce desired levels of inter‐story drifts while reducing seismic forces as well. To attain a nonlinear elastic behavior, use could also be made by the negative stiffness device introduced by others. As inter‐story drifts are reduced to desired levels, the methodology could naturally be used as part of the performance‐based design framework. The values of capping forces and damping coefficients serve as design variables. The capping forces are the yield forces in yielding members and the maximum forces in nonlinear elastic members. The procedure relies on analysis tools only, hence, could be easily incorporated into the practical design process. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-08-21T02:29:10.171833-05:
      DOI: 10.1002/stc.1688
  • Probabilistic identification of simulated damage on the Dowling Hall
           footbridge through Bayesian finite element model updating
    • Authors: Iman Behmanesh; Babak Moaveni
      Pages: n/a - n/a
      Abstract: This paper presents a probabilistic damage identification study on a full‐scale structure, the Dowling Hall footbridge, through a Bayesian finite element (FE) model updating. The footbridge is located at Tufts University and is equipped with a continuous monitoring system that measures its ambient acceleration response. A set of data is recorded once every hour or when triggered by large vibrations. The modal parameters of the footbridge are extracted from each set of data and are used for FE model updating. In this study, effects of physical damage are simulated by loading a small segment of the footbridge deck with concrete blocks. The footbridge deck is divided into five segments in an FE model of the test structure, and the added mass on each segment is considered as an updating parameter. Overall, 72 sets of data are collected during the loading period, and different subsets of these data are used to find the location and extent of the damage (added mass). The adaptive Metropolis–Hastings algorithm with adaption on the proposal probability density function is successfully used to generate Markov Chains for sampling the posterior probability distributions of the five updating parameters. Effects of the number of data sets used in the identification process are investigated on the posterior probability distributions of the updating parameters. The probabilistic model updating framework accurately predicts the simulated damage and the level of confidence on the obtained results. The maximum a‐posteriori estimates of damage in the probabilistic approach are found to be in good agreement with their corresponding deterministic counterparts. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-08-05T04:08:24.941908-05:
      DOI: 10.1002/stc.1684
  • Multi‐sensing NDT for damage assessment of concrete masonry walls
    • Authors: Fuad Khan; Satish Rajaram, Prashanth A. Vanniamparambil, Mohammad Bolhassani, Ahmad Hamid, Antonios Kontsos, Ivan Bartoli
      Pages: n/a - n/a
      Abstract: This paper presents a hybrid non‐destructive testing (NDT) approach based on (non‐contact) infrared thermography (IRT), (passive) acoustic emission (AE), and (active) ultrasonic (UT) techniques for effective damage assessment of partially grouted concrete masonry walls (PGMW). This hybrid monitoring approach could be implemented for the health monitoring of concrete masonry structures. The implementation of this system assists the cross validation of in‐situ recorded information for structural damage assessment. NDT was performed on PGMW subjected to cyclic horizontal loading. The obtained IRT, AE, and UT results successfully monitored the progressive damage process throughout the loading history. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-07-28T23:26:04.332182-05:
      DOI: 10.1002/stc.1680
  • Compressive sensing‐based lost data recovery of fast‐moving
           wireless sensing for structural health monitoring
    • Authors: Yuequan Bao; Yan Yu, Hui Li, Xingquan Mao, Wenfeng Jiao, Zilong Zou, Jinping Ou
      Pages: n/a - n/a
      Abstract: Wireless sensor technology‐based structural health monitoring (SHM) has been widely investigated recently. This paper proposes a fast‐moving wireless sensing technique for the SHM of bridges along a highway or in a city in which the wireless sensor nodes are installed on the bridges to automatically acquire data, and a fast‐moving vehicle with an onboard wireless base station periodically collects the data without interrupting traffic. For the fast‐moving wireless sensing technique, the reliable wireless data transmission between the sensor nodes and the fast‐moving base station is one of the key issues. In fast‐moving states, the data packet loss rates during wireless data transmission between the moving base station and the sensor nodes will increase remarkably. In this paper, the data packets loss in the fast‐moving states is first investigated through a series of experiments. To solve the data packets loss problem, the compressive sensing (CS)‐based lost data recovery approach is proposed. A field test on a cable‐stayed bridge is performed to further illustrate the data packet loss in the fast‐moving wireless sensing technique and the ability of the CS‐based approach for lost data recovery. The experimental and field test results indicate that the Doppler effect is the main reason causing data packet loss for the fast‐moving wireless sensing technique, and the feasibility and efficiency of the CS‐based lost data recovery approach are validated Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-07-28T23:24:48.913065-05:
      DOI: 10.1002/stc.1681
  • Partially bonded fiber‐reinforced elastomeric isolators
    • Authors: Niel C. Van Engelen; Peyman M. Osgooei, Michael J. Tait, Dimitrios Konstantinidis
      Pages: n/a - n/a
      Abstract: Although stable unbonded fiber‐reinforced elastomeric isolators (SU‐FREIs) have desirable characteristics for seismic isolation, the unbonded application also introduces limitations in comparison with bonded elastomeric isolators. SU‐FREIs are not capable of resisting tensile forces, making SU‐FREIs unsuited for situations where overturning is of concern or where large vertical accelerations are anticipated. Furthermore, as SU‐FREIs rely on friction to transfer horizontal forces, the isolator could potentially slip under certain loading conditions, resulting in permanent displacements. This paper proposes that concerns over the transfer of tensile forces and potential slip can be addressed by partially bonding the SU‐FREI to the upper and lower supports. In this way, partially bonded FREIs (PB‐FREIs) not only retain the beneficial characteristics of an unbonded FREI but also inherit characteristics of a bonded isolator; notably tensile and horizontal forces can be transferred through the partial bond. Experimental results from isolators tested unbonded and partially bonded under vertical compression are used to evaluate a finite element model. The experimental data and finite element analysis demonstrate that portions of a FREI can be bonded without substantially altering the rollover characteristics of the isolator within the range of average vertical compressive and tensile stresses considered. Despite an unconventional deformed shape under tensile vertical stress, the horizontal force–displacement relationship exhibits negligible deviation from a conventional unbonded SU‐FREI under a compressive vertical stress. It is postulated that with further development, partially bonded FREIs can retain the beneficial characteristics of unbonded FREIs while addressing concerns over tensile forces and slip. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-07-28T23:12:01.695306-05:
      DOI: 10.1002/stc.1682
  • Assessing uncertainty in operational modal analysis incorporating multiple
           setups using a Bayesian approach
    • Authors: Feng‐Liang Zhang; Siu‐Kui Au, Heung‐Fai Lam
      Pages: n/a - n/a
      Abstract: A Bayesian statistical framework was previously developed for modal identification of well‐separated modes incorporating ambient vibration data, that is, operational modal analysis, from multiple setups. An efficient strategy was developed for evaluating the most probable value of the modal parameters using an iterative procedure. As a sequel to the development, this paper investigates the posterior uncertainty of the modal parameters in terms of their covariance matrix, which is mathematically equal to the inverse of the Hessian of the negative log‐likelihood function evaluated at the most probable value. Computational issues arising from the norm constraint of the global mode shape are addressed. Analytical expressions are derived for the Hessian so that it can be evaluated accurately and efficiently without resorting to finite difference. The proposed method is verified using synthetic and laboratory data. It is also applied to field test data, which reveals some challenges in operational modal analysis incorporating multiple setups. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-07-28T23:10:34.37728-05:0
      DOI: 10.1002/stc.1679
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