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  Subjects -> ENERGY (Total: 261 journals)
    - ENERGY (173 journals)
    - ENERGY: GENERAL (8 journals)
    - NUCLEAR ENERGY (23 journals)
    - PETROLEUM AND GAS (47 journals)
    - WIND ENERGY (10 journals)

ENERGY (173 journals)                  1 2 | Last

Advances in Building Energy Research     Hybrid Journal   (Followers: 11)
Advances in Energy and Power     Open Access   (Followers: 1)
Advances in High Energy Physics     Open Access   (Followers: 12)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 15)
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: 10)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Solar Energy     Hybrid Journal   (Followers: 12)
Archives of Thermodynamics     Open Access   (Followers: 4)
Artificial Photosynthesis     Open Access  
Atomic Energy     Hybrid Journal   (Followers: 6)
Atoms for Peace: an International Journal     Hybrid Journal   (Followers: 3)
Biofuels     Hybrid Journal   (Followers: 7)
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: 7)
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: 10)
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: 1)
Electrical and Power Engineering Frontier     Open Access   (Followers: 8)
Electronic Journal of Energy & Environment     Open Access   (Followers: 9)
Energy     Partially Free   (Followers: 23)
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: 9)
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 Policy     Partially Free   (Followers: 47)
Energy Prices and Taxes     Full-text available via subscription   (Followers: 5)
Energy Procedia     Open Access   (Followers: 3)
Energy Science & Engineering     Open Access   (Followers: 4)
Energy Science and Technology     Open Access   (Followers: 12)
Energy Strategy Reviews     Partially Free   (Followers: 5)
Energy Studies Review     Open Access   (Followers: 3)
Energy Systems     Hybrid Journal   (Followers: 10)
Energy Technology     Partially Free   (Followers: 3)
Energy, Sustainability and Society     Open Access   (Followers: 17)
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  
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: 1)
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: 11)
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: 8)
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 Critical Infrastructure Protection     Hybrid Journal   (Followers: 5)
International Journal of Electric and Hybrid Vehicles     Hybrid Journal   (Followers: 4)
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: 7)
International Journal of Green Energy     Hybrid Journal   (Followers: 5)
International Journal of Hydrogen Energy     Partially Free   (Followers: 9)
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)
International Journal of Nuclear Hydrogen Production and Applications     Hybrid Journal   (Followers: 1)
International Journal of Nuclear Knowledge Management     Hybrid Journal   (Followers: 2)
International Journal of Power and Energy Conversion     Hybrid Journal   (Followers: 3)
International Journal of Regulation and Governance     Hybrid Journal   (Followers: 2)

        1 2 | Last

Journal Cover Structural Control and Health Monitoring
   [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  [1604 journals]   [SJR: 1.148]   [H-I: 21]
  • 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
           responses
    • 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
           measurement
    • 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
           acceleration
    • 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
           structures
    • 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
           excitation
    • 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
           beams
    • 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
       
  • Issue Information
    • Pages: i - ii
      Abstract: No abstract is available for this article.
      PubDate: 2014-10-13T22:31:54.128971-05:
      DOI: 10.1002/stc.1618
       
  • Influence of isolation hysteresis on the seismic performance of isolated
           buildings
    • 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
           response
    • 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
           decomposition
    • 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
           (PB‐FREIs)
    • 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
       
  • Damage localization based on symbolic time series analysis
    • Authors: Mehrisadat Makki Alamdari; Bijan Samali, Jianchun Li
      Pages: n/a - n/a
      Abstract: The objective of this paper is to localize damage in a single or multiple state at early stages of development on the basis of the principles of symbolic dynamics. Symbolic time series analysis (STSA) of noise‐contaminated responses is used for feature extraction to detect and localize a gradually evolving deterioration in the structure according to the changes in the statistical behaviour of symbol sequences. Basically, in STSA, statistical features of the symbol sequence can be used to describe the dynamic status of the system. Symbolic dynamics has some useful characteristics making it highly demanded for implementation in real‐time observation application such as SHM. First, it significantly reduces the dimension of information and provides information‐rich representation of the underlying data. Second, symbolic dynamics and the set of statistical measures built upon it represent a solid framework to address the main challenges of the analysis of nonstationary time data. Finally, STSA often allows capturing the main features of the underlying system whilst alleviating the effects of harmful noise. The method presented in this paper consists of four primary steps: (i) acquisition of the time series data; (ii) creating the symbol space to produce symbol sequences on the basis of the wavelet transformed version of time series data; (iii) developing the symbol probability vectors to achieve anomaly measures; and (iv) localizing damage on the basis of any sudden variation in anomaly measure of different locations. The method was applied on a flexural beam and a 2‐D planar truss bridge subjected to varying Gaussian excitation in presence of 2% white noise to examine the efficiency and limitations of the method. Simulation results under various damage conditions confirmed the efficiency of the proposed approach for localization of gradually evolving deterioration in the structure; however, for the future work, the method needs to be verified by experimental data. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-07-28T22:53:22.459024-05:
      DOI: 10.1002/stc.1683
       
  • Innovative method of empirical mode decomposition as spatial tool for
           structural damage identification
    • Authors: D. Mallikarjuna Reddy; Praveen Krishna, Sathesa
      Pages: n/a - n/a
      Abstract: A new approach to sensitize detecting structural damage using empirical mode decomposition (EMD) of the spatial signals is proposed. The difference of undamaged and damaged spatial strain and strain energy data for the beam and bridge modes is processed through the EMD, which yields the respective IMF1, which shows that damage location can be identified distinctively for as low as 0.01% reduction in elemental stiffness of beam discretized with 30 elements. An analysis was also carried out for a two‐dimensional bridge model (I‐40). It can detect damage sensitivity up to 0.5% loss in stiffness of the bridge. EMD as a spatial analysis tool seems to be the most sensitive among all methods currently available. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-07-07T04:57:24.518876-05:
      DOI: 10.1002/stc.1676
       
  • Seismic evaluation and structural control of the historical Beylerbeyi
           Palace
    • Authors: Fuat Aras; Gulay Altay
      Pages: n/a - n/a
      Abstract: The Beylerbeyi Palace was built between 1861 and 1865 on the Asian shore of Istanbul, and it is within the cultural heritage treasury of the world. Recent earthquakes in the Mediterranean basin have highlighted the particular vulnerability of historic masonry buildings and the need of properly defining retrofitting measures. In this respect, structural behaviour and the earthquake performance of the palace have been investigated. It is seen that the inherent dynamic properties of the palace make it vulnerable to earthquake ground shaking. In order to reduce the affect of ground shaking, the use of base isolation system has been investigated. It is determined that base isolation can be used to reduce the earthquake effects on the palace and ensure the structural performance under maximum considered earthquake. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-06-27T02:20:38.559761-05:
      DOI: 10.1002/stc.1677
       
  • Experiments for seismic damage detection of a RC frame using ambient and
           forced vibration records
    • Authors: Jesús Valdés‐González; Jaime De‐la‐Colina, Carlos Alberto González‐Pérez
      Pages: n/a - n/a
      Abstract: This paper presents an experimental study conducted on a two‐story RC frame that was progressively damaged until it reached a significant structural damage. The RC frame was subjected to increasing dynamic load stages typical of growing‐intensity earthquake ground motions. The frame was excited with a testing pendulum, which is a device that excited the structure attached to the pendulum platform with a harmonic motion along one horizontal direction at selected frequencies. For each damage level, ambient and forced vibration tests were performed, and dynamic properties of the frame were estimated. It was possible to characterize the damage level of the RC frame in terms of the simple statistical correlation between a pair of frequency response functions obtained for the initial damage condition and the subsequent stages. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-06-26T03:11:51.111251-05:
      DOI: 10.1002/stc.1678
       
  • Localization of acoustic emission sources in structural health monitoring
           of masonry bridge
    • Authors: Qinghua Han; Jie Xu, Alberto Carpinteri, Giuseppe Lacidogna
      Pages: n/a - n/a
      Abstract: The application of the acoustic emission (AE) technique to monitoring the crack characterization in masonry structures is investigated in this paper. An improved approach, modified from the classical crack source localization method, is proposed to provide more reliable crack locations in masonry structures. The introduced parameter, degree of inhomogeneity ξ in the modified method, can help to decrease the unavoidable propagation delay related to refraction due to the layers in masonry material. The modified method is successfully applied to the AE source detection during the pencil-lead break test and the central pier settlement test of a masonry model bridge to analyze the crack pattern. It is shown that the proposed method is a reliable tool for crack source location in masonry structures. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-06-13T00:27:47.547722-05:
      DOI: 10.1002/stc.1675
       
  • Optical fiber-based sensors with flexible encapsulation for pavement
           behavior monitoring
    • Authors: Wanqiu Liu; Huaping Wang, Zhi Zhou, Xiaoying Xing, Dandan Cao, Zhen Jiang
      Pages: n/a - n/a
      Abstract: Owing to the increasing needs for robust highway pavement structural monitoring tools with high accuracy and functionality, this paper introduces some results from the research on developing optical fiber-based pavement behavior monitoring sensors. A new flexible encapsulation technique for optical fiber sensing element has been proposed to help the sensor withstand the harsh working environment and guarantee measuring accuracy. Both fiber Bragg grating and Brillouin optical time domain analysis/reflectometry-based sensors have been produced in a lab with the proposed encapsulation for high accuracy and distributed measurement, respectively. The precision of the fiber Bragg grating-based sensor has been specially calibrated in a lab. Lab and field tests have been carried out to study the effectiveness of the proposed sensors. It has been found that the proposed sensors have high survival rate (>75%) and are efficient for pavement structural behavior monitoring and damage detection. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-06-05T00:27:57.9533-05:00
      DOI: 10.1002/stc.1674
       
  • Inference of bond slip in prestressed tendons in concrete bridge girders
    • Authors: Siu Chun M. Ho; Liang Ren, Emad Labib, Aadit Kapadia, Yi-Lung Mo, Hongnan Li, Gangbing Song
      Pages: n/a - n/a
      Abstract: Prestressed concrete (PC) bridge girders have extra flexural strength due to embedded prestressing tendons. The level of strength depends on the integrity of the concrete-tendon bond in pretensioned PC structures, and this bond can be degraded in the presence of an adequately large mechanical force or over time because of accumulated damage. Bond degradation is characterized by the bond slip of the tendon from the host concrete, and in regards to PC structures, bond slip has only been measured from a global perspective. In this paper, a novel method was developed to measure for the first time the local strain of a prestressing tendon during bond slip. Fiber Bragg grating-based strain sensors were installed directly onto prestressing tendons within a PC girder to provide a local perspective of bond slip as the girder was loaded to failure. Measurement of the local strains in selected tendons, from the beginning of bond slip to the complete loss of the concrete-tendon bond, and the failure of the girder was enabled by the method. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-06-02T20:07:43.265258-05:
      DOI: 10.1002/stc.1669
       
  • Nonlinear data-driven computational models for response prediction and
           change detection
    • Authors: Armen Derkevorkian; Miguel Hernandez-Garcia, Hae-Bum Yun, Sami F. Masri, Peizhen Li
      Pages: n/a - n/a
      Abstract: Data are used from three relatively large-scale experimental soil-foundation-superstructure interaction (SFSI) systems to develop reduced-order computational models for response prediction and change-detection relevant to structural health monitoring and computational mechanics. The three systems under consideration consist of identical superstructures with: (i) fixed base; (ii) box foundation; and (iii) pile foundation. The three SFSI systems were developed and experimentally tested at Tongji University. In the first part of the study, a computational time-marching prediction framework is proposed by incorporating trained neural network(s) within an ordinary differential equation solver and dynamically predicting the response (i.e., displacement and velocity) of the SFSI systems to various earthquake excitations. Two approaches are investigated: global approach and subsystem approach. Both approaches are tested and validated with linear and nonlinear systems, and their respective pros and cons are discussed. In the second part of the study, the trained neural networks from the global approach are further used for change-detection in the SFSI systems. The detected changes in the systems are then quantified through a measure of a normalized error index. Challenges related to the physical interpretation of the quantified changes in the SFSI systems are addressed and discussed. It is shown that the general procedures adopted in this paper provide a robust nonlinear model that is reliable for computational studies, as well as furnishing a robust tool for detecting and quantifying inherent change in the system. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-05-30T01:55:40.559884-05:
      DOI: 10.1002/stc.1673
       
  • System identification of a historic swing truss bridge using a wireless
           sensor network employing orientation correction
    • Authors: Soojin Cho; Ryan K. Giles, Billie F. Spencer
      Pages: n/a - n/a
      Abstract: System identification was performed on the swing span of a steel truss bridge dating from 1896 using acceleration data collected from a wireless sensor network (WSN). The swing span can rotate 360° to allow river traffic to pass through the locks located under the bridge. The WSN installed on the swing span consists of 23 nodes that measure synchronized tri-axial acceleration. Five days of measured data were segmented according to three functional positions of the span (locked facing downstream, locked facing upstream, swung for river traffic) and load conditions. Subsequently, the modal parameters corresponding to the bridge's three functional positions were obtained using frequency domain decomposition method. The initial system identification of the bridge resulted in significant anomalies, in comparison with the finite element (FE) model. To improve the accuracy of the overall identification results, the sensor orientation correction technique is proposed for the measured data from the WSN. The improvement has been verified by comparing the orientation-corrected mode shapes with non-corrected mode shapes and FE mode shapes using the modal assurance criterion values. Analysis of the modal parameters inferred that the boundary conditions for the bridge positions are different because of the interaction of the locking mechanism with the abutments in those positions. The proposed approach for system identification, including sensor orientation correction, is to be used as part of the comprehensive structural heath monitoring strategy for this historic structure. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-05-30T01:11:21.812753-05:
      DOI: 10.1002/stc.1672
       
  • Performance of fiber-reinforced elastomeric base isolators under cyclic
           excitation
    • Authors: Animesh Das; Anjan Dutta, Sajal K. Deb
      Pages: n/a - n/a
      Abstract: This paper presents three-dimensional finite element models for the analysis of square fiber-reinforced elastomeric isolators (FREI) subjected to cyclic horizontal displacement and constant vertical load. Direction of applied displacement has been varied to evaluate their influence on the isolator performance. Both bonded and un-bonded boundary conditions at the top and bottom contact surfaces of isolator have been simulated in the analysis. It is observed that the un-bonded FREI are more effective in seismic isolation as compared with bonded FREI, and stresses developed under lateral displacement are also significantly lower in un-bonded FREI. Experimental validation has been carried out for un-bonded isolators and very good agreement is observed in terms of mechanical properties and deformed configuration. In the absence of any close form solution of un-bonded FREI due to its complex deformation pattern, finite element solution is observed to be sufficiently accurate for arriving at the design parameters of an isolator. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-05-21T01:15:11.81426-05:0
      DOI: 10.1002/stc.1668
       
  • Optimal design of distributed tuned mass dampers for passive vibration
           control of structures
    • Authors: F. Yang; R. Sedaghati, E. Esmailzadeh
      Pages: n/a - n/a
      Abstract: The distributed tuned mass damper (DTMD) system consists of multiple tuned mass dampers, which are designed to suppress the undesirable structural vibration over a bandwidth centered at a particular tuned frequency. In this study, an innovative practical approach to optimally design the DTMD system has been proposed. Comparisons were made between the optimal DTMD system, obtained based on the proposed design approach, and those using the conventional design approach. The superior performance and robustness of the optimally designed DTMD system based on the proposed approach compared with that based on the conventional approach have been demonstrated through illustrative examples. It has been shown that the proposed design approach provide a simple, clear, and straightforward way to effectively attain the optimum parameters of the DTMD system. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-05-21T01:12:10.595634-05:
      DOI: 10.1002/stc.1670
       
  • Amplitude and frequency independent cable damping of Sutong Bridge and
           Russky Bridge by magnetorheological dampers
    • Authors: Felix Weber; Hans Distl
      Pages: n/a - n/a
      Abstract: Two control approaches for magnetorheological (MR) dampers on cables based on collocated control without state estimation are formulated, which generate amplitude and frequency independent cable damping: cycle energy control and controlled viscous damping (CVD). The force tracking is solved by the inverted Bingham model whose parameters are fitted as function of current and frequency. Cycle energy control and CVD are experimentally validated by hybrid simulations and free decay tests on stay cables of the Sutong Bridge, China, and the Eiland Bridge, the Netherlands. The implementation of CVD on the Russky Bridge, Russia, includes two novelties: the force tracking also takes the actual MR damper temperature into account to ensure precise force tracking for MR damper temperatures −40 to +60 °C and the decentralised real-time control units with pulse width current modulation are installed next to each MR damper to avoid long direct current (DC) power lines with associated losses and thereby minimise power consumption. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-05-21T00:42:33.391893-05:
      DOI: 10.1002/stc.1671
       
  • Fuzzy logic control of a stiffness-adaptable seismic isolation system
    • Authors: Tzu-Kang Lin; Lyan-Ywan Lu, Hsun Chang
      Pages: n/a - n/a
      Abstract: Traditional passive isolation systems have been shown to provide satisfactory seismic mitigation performance under typical far-field earthquake conditions. However, because of the untunable designated isolation period, the performance of these systems is still strongly affected by the low-frequency resonance phenomenon observed during near-fault earthquakes, which are usually dominated by a long-duration impulse. The use of semi-active isolation systems with variable stiffness, which are usually equipped with a customized control algorithm to determine the isolation stiffness or period in real time, could be a promising solution to overcome this problem. To realize this technology, this study develops a smart isolation system that combines the leverage-type stiffness-controllable isolation system (LSCIS) with a simple fuzzy logic control (FLC). Because the proposed FLC merely requires feedback from the velocity and displacement responses of the isolation base, it is quite easily implemented. Theoretical analysis shows that the extreme displacement of the isolation level caused by near-fault seismic waves can be mitigated by the proposed system with tolerable acceleration response variations compared with that of the traditional passive isolation system. The movement of the pivot point of the LSCIS can also be adjusted to address the inherent hardware constraint that limits its practical application. Experimental verification conducted on a shake table further demonstrates the feasibility of integrating the LSCIS system with FLC after proper consideration of the friction effect generated by the leverage mechanism and the inevitable time delay effect. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-05-15T02:48:38.057729-05:
      DOI: 10.1002/stc.1667
       
  • Passive control of floating offshore wind turbine nacelle and spar
           vibrations by multiple tuned mass dampers
    • Authors: Van-Nguyen Dinh; Biswajit Basu
      Pages: n/a - n/a
      Abstract: This paper investigates the use of single and multiple tuned mass dampers (TMDs) for passive control of edgewise vibrations of nacelle/tower and spar of spar-type floating wind turbines (S-FOWTs). Uncontrolled and controlled mathematical models of the S-FOWT are developed by using Euler-Lagrangian energy formulations. In these models, the aerodynamic properties of the blade, variable mass and stiffness, gravity, the interactions among the blades, nacelle, spar and mooring system, the hydrodynamic effects, the restoring moment, and the buoyancy force are considered. The vibrations of the blades, nacelle, tower, and spar are coupled in all degrees of freedom and in all inertial, dissipative, and elastic components. In the controlled model, several set of horizontal TMDs are placed in the spar at various depths and the coupling of these TMDs with the nacelle and spar motions is considered. The control effectiveness is evaluated by the reduction of the root-mean-square and maximum response. The control feasibility is examined by using the spar sinking and the TMD maximum strokes. The investigations using nonlinear time–domain simulation show that a single TMD can reduce up to 40% of the nacelle sway displacement and the spar roll, and that the reduction observed with multiple TMDs is 50%. The influence of the spar TMD is more significant than that of the nacelle TMD. The spar TMDs are less effective when their positions are lower. In all the cases studied, good heave performance of the S-FOWT is maintained. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-05-15T01:55:11.246845-05:
      DOI: 10.1002/stc.1666
       
  • Retest of Neoprene seismic isolation bearings after 30 years
    • Authors: Niel C. Van Engelen; James M. Kelly
      Pages: n/a - n/a
      Abstract: This paper describes the retest of a set of Neoprene (Polychloroprene) steel reinforced elastomeric isolator bearings that were originally tested as part of an experimental program in 1981. The original bearings were tested on a shake table as a demonstration of the feasibility of base isolation for the seismic protection of buildings. Two types of bearings were provided, and not all were used. The unused bearings were stored unloaded at room temperature for over 30 years. Although there has been a very substantial improvement in the number and quality of the instrumentation available to the test program over the span of 30 years, it is possible to compare the results of relatively similar shake table tests on the bearings. The shake table tests are used to assess the changes in the horizontal stiffness and damping values for the bearings over this period. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-05-08T01:30:31.988429-05:
      DOI: 10.1002/stc.1665
       
  • Health monitoring sensor placement optimization for Canton Tower using
           immune monkey algorithm
    • Authors: Ting‐Hua Yi; Hong‐Nan Li, Xu‐Dong Zhang
      Pages: n/a - n/a
      Abstract: Sensor placement is an integral component in the design of an effective and reliable structural health monitoring system for large‐scale civil engineering structures. In this paper, a novel hybrid optimization algorithm, that is, immune monkey algorithm (IMA), by combining the monkey algorithm with the immune algorithm, is proposed to solve the optimal sensor placement problem. In the proposed algorithm, the dual‐structure coding method is designed and adopted for the representation of design variables and a chaos‐based approach is presented to initialize the monkey population. In addition, some improved strategies such as the advanced climb process, immune selection, clonal proliferation, and immune renewal are defined to maintain population diversity and inhibit degeneracy during evolution. The effectiveness and reliability of the proposed IMA is demonstrated by designing the sensor arrays of the Canton Tower, the second highest TV tower in the world. Numerical investigations presented clearly suggest that the proposed hybrid IMA outperforms the original monkey algorithm implementations both in terms of generating optimal solutions as well as faster convergence. The proposed algorithm can easily be extended to other multiple global optimization problems. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-04-29T00:30:25.367951-05:
      DOI: 10.1002/stc.1664
       
  • Shaking table investigation of a novel, low‐cost, base isolation
           technology using recycled rubber
    • Authors: Andrea Calabrese; Mariacristina Spizzuoco, Giorgio Serino, Gaetano Della Corte, Giuseppe Maddaloni
      Pages: n/a - n/a
      Abstract: This paper details the findings of an experimental program that assessed the seismic performances of a novel low‐cost base isolation device. The proposed bearings are referred to as recycled rubber–fiber‐reinforced bearings (RR‐FRBs). Devices composed of a low‐cost recycled elastomer and reinforced with fiber sheets were manufactured and tested. The main revolutionary concepts investigated in this study are as follows: low‐performance elastomers can be used to produce rubber isolators, and vulcanization can be prevented by bonding different layers with an elastic compound. This study addresses all design and technical aspects related to the implementation of the proposed base isolation system. Shaking table tests showed a significant improvement in the seismic performance of an RR‐FRB isolated building with respect to a corresponding fixed‐base structure. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-04-27T22:49:08.803865-05:
      DOI: 10.1002/stc.1663
       
  • New damage indices and algorithm based on square time–frequency
           distribution for damage detection in concrete piers of railroad bridges
    • Authors: H. R. Ahmadi; F. Daneshjoo, N. Khaji
      Pages: n/a - n/a
      Abstract: This paper presents a new algorithm based on square time–frequency distribution to detect damages in concrete piers of railroad bridges. In addition, two new damage indices are proposed in this research. The algorithm and damage indices are described and corroborated using finite element model of Qotour railroad bridge. To create the finite element model according to the current condition of the Qotour railroad bridge, extensive in situ measurement results and laboratory tests were used. Some seismic damages were considered in the concrete piers of the model. The results indicate that the algorithm and damage indices can identify all damages from severe to small accurately. The proposed algorithm and damage indices are shown to be not sensitive to noise and even in case of noise‐polluted response signal are working properly. The proposed algorithm only uses the response signals without the need for recording the excitation forces. In addition, according to the algorithm, there is no need to create an analytical model of the bridge for damage detection. This feature in modeling of bridge structures and especially complex bridge, which is associated with problems, is very useful. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-04-27T22:27:05.689316-05:
      DOI: 10.1002/stc.1662
       
  • Seismic response analyses of an asymmetric base‐isolated building
           during the 2011 Great East Japan (Tohoku) Earthquake
    • Authors: Dionysius M. Siringoringo; Yozo Fujino
      Pages: n/a - n/a
      Abstract: Analysis of strong motion recordings of a base‐isolated building during the March 11, 2011, Great East Japan (Tohoku) Earthquake is reported in this paper. The building, located in Tokyo Bay area, is an asymmetric L‐shaped structure consisting of seven‐story and 14‐story building with vertical opening. Vibration monitoring system was installed on the building in 2010, and seismic responses were recorded including the strongest shaking (peak ground acceleration 0.80–1.40 m/s2) experienced during the main shock of March 11, 2011, Great East Japan Earthquake. The building survived the earthquake without structural damage. The study in this paper includes response analysis, system identification, and seismic performance evaluation of the structure, especially performance of base‐isolation system. The study shows that despite considerable shift in effective frequency of the building due to the increase in flexibility of isolation system during the main shock, large acceleration was recorded on the superstructure with the peak floor accelerations of nearly 300 cm/s2. Two factors contribute to this cause: one is the characteristics of the building where torsional modes dominate the seismic response of upper stories and the other is resonance, where dominant frequencies of ground motions coincide with the natural frequencies of torsional modes. Moreover, analysis shows that torsional modes were not significantly influenced by performance of base isolation, so that even though the base isolation has functioned properly, the upper stories still experienced large floor accelerations. The paper also discusses long‐term observation of seismic responses during aftershocks and various levels of earthquakes between 2010 and 2012. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-04-11T00:41:15.630181-05:
      DOI: 10.1002/stc.1661
       
  • Automatic baseline correction of strain gauge signals
    • Authors: Shengfa Miao; Eddy Koenders, Arno Knobbe
      Pages: n/a - n/a
      Abstract: Considerable research effort has been devoted to distinguishing changes caused by the environmental variability from changes due to structural damage, but unfortunately, investigations studying the operational variability, such as traffic events, have been lacking. In order to obtain signals of high quality, we need to deal with baseline drift problems mainly caused by temperature changes and traffic jams. In this paper, we present a new baseline correction method, the most‐crossing method, to deal with the baseline of the strain signals collected from a sensor network installed on a concrete bridge. It is a piece‐wise method based on probability theory. This method needs only a few manual parameter selection and can be used automatically for real time baseline correction. We compare the performance of the most‐crossing method with that of the first derivative method and the iterative polynomial method. The experimental results indicate that the most‐crossing method is superior in dealing with civil engineering signals. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-04-10T01:12:21.39225-05:0
      DOI: 10.1002/stc.1658
       
  • Railway infrastructure damage detection using wavelet transformed
           acceleration response of traversing vehicle
    • Authors: Daniel Cantero; Biswajit Basu
      Pages: n/a - n/a
      Abstract: This paper proposes the use of vertical accelerations of a moving train to detect local track irregularities produced by weaker sections of the infrastructure. By analysing the vehicle accelerations using the wavelet transform, it is possible to clearly identify the location of damaged sections. A wavelet‐based indicator is proposed to facilitate an algorithm for recognition of deteriorated segments. The proposed indicator is validated by means of a 2‐DOF vehicle model excited by randomly generated track irregularities together with the presence of various local track defects. A Monte Carlo analysis is performed to evaluate the performance of the proposed indicator for a variety of model parameters, including vehicle mechanical properties, shape of isolated track irregularities and levels of damage. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-04-10T01:09:26.440852-05:
      DOI: 10.1002/stc.1660
       
  • Ultrasonic guided waves for monitoring corrosion in submerged plates
    • Authors: Sandeep Sharma; Abhijit Mukherjee
      Pages: n/a - n/a
      Abstract: This paper reports a non‐contact, in‐situ and non‐destructive corrosion monitoring methodology for submerged plates using ultrasonic guided waves. Specific surface sensitive and core sensitive guided wave modes are utilized for monitoring plates undergoing accelerated impressed current corrosion in the presence of chlorides. A combination of the selected guided wave modes could effectively discern various corrosion mechanisms occurring in plates. Along with the ultrasonic signals, mass loss, stress–strain behaviour and tensile strength of the plates at different stages of corrosion have been monitored. Algebraic relationships between the ultrasonic readings and other parameters have been developed. This investigation should be useful in developing a non‐destructive technique for monitoring progressive corrosion in plates and assessing their deterioration in strength, stiffness and mass loss that would help in the estimation of residual life. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-04-04T00:10:26.847728-05:
      DOI: 10.1002/stc.1657
       
  • Application of artificial neural networks for compounding multiple damage
           indices in Lamb‐wave‐based damage detection
    • Authors: Ziemowit Dworakowski; Lukasz Ambrozinski, Pawel Packo, Krzysztof Dragan, Tadeusz Stepinski
      Pages: n/a - n/a
      Abstract: This paper presents a novel approach to the problem of health monitoring of aircraft structures using Lamb waves. Piezoelectric sensors, embedded in the aircraft sheathing, generate Lamb waves with the aim to monitor the structural integrity of complex structure parts. The ultrasonic signals obtained from the sensor pairs arranged in pitch‐catch configuration are used for the calculation of a number of different damage indices. The damage indices are then used as inputs for a classifier employing an artificial neural network (ANN) that is trained to perform structure condition assessment. Efficiency of the ANN classifier trained on artificial data generated from the numerical simulations performed using linear interaction simulation approach is investigated. The resulting classification results are compared with those obtained for the ANN trained on experimental data from the real specimens. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-04-03T23:57:18.300917-05:
      DOI: 10.1002/stc.1659
       
  • Computationally efficient design of optimal strategies for controllable
           damping devices
    • Authors: Mahmoud Kamalzare; Erik A. Johnson, Steven F. Wojtkiewicz
      Pages: n/a - n/a
      Abstract: The development of control strategies for controllable passive dampers — ‘semiactive’ damping devices — is complicated by the nonlinear and dissipative nature of the devices and the nonlinear nature of the closed‐loop system with any form of parametric feedback control. Control design for nonlinear systems is often achieved by designing a control for a linearized model since strategies for linear systems are straightforward. One such approach is clipped‐optimal control in which the desired damper forces are determined from an optimal controller (e.g., linear quadratic regulator, linear quadratic Gaussian, H2 and H∞), which is designed assuming that the damping devices are fully linear actuators that can exert any forces (dissipative or nondissipative), and a secondary bang–bang controller commands the controllable damper to exert forces as close as possible to the desired forces. However, designs using any linearized model generally result in suboptimal (and sometimes very poor) performance because the linear actuator assumption differs from the actual implementation with a dissipative damping device. Thus, one must generally resort to a large‐scale parameter study in which the nonlinear system is simulated many times to determine control strategies that are actually optimal for the nonlinear controlled closed‐loop system. This paper demonstrates how an approach developed by the authors, which can reduce the model of a system with local modifications to a lower order set of Volterra integral equations in the modification forces, can significantly decrease the computational burden of a complex control design study for controllable dampers. The approach is first adapted to use a state feedback control with a bang–bang on–off secondary controller. Then, the structural and damping device models are detailed. The optimal semiactive control design is demonstrated via both a parameter study and an optimization algorithm. Numerical examples demonstrate that the approach is effective and, compared with a conventional simulation approach, can reduce computation time by two orders of magnitude. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-03-17T01:47:04.095831-05:
      DOI: 10.1002/stc.1649
       
  • Active tendons control of structures using block pulse functions
    • Authors: Hosein Ghaffarzadeh; Amir Younespour
      Pages: n/a - n/a
      Abstract: Structural active control is one of the most efficient systems available to protect building structures from destructive effects of earthquakes. Active control efficiency is highly dependent on control algorithm. One of the most important and challenging components of structural control is the development of an accurate analytical approach having less computational expenses. Block pulse functions have been studied and applied frequently in recent years as a basic set of functions for signal characterizations in systems science and control. The proposed method evolves minimizing computational expenses of analytical approaches by a novel method to suppress the responses of the structure based on block pulse functions. To prove the validity and feasibility of the proposed control method, numerical simulations of earthquake‐excited 10‐story shear buildings with active tendons are performed, and comparative results are presented. The uncontrolled and controlled responses of structural system are obtained by using the proposed method and compared with linear quadratic regulator method. The results reveal that the proposed method can be beneficial in reducing seismic responses of structures with high accuracy and less computational expenses. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-03-14T02:11:05.081948-05:
      DOI: 10.1002/stc.1656
       
  • A European Association for the Control of Structures joint perspective.
           Recent studies in civil structural control across Europe
    • Authors: Biswajit Basu; Oreste S. Bursi, Fabio Casciati, Sara Casciati, Andrea E. Del Grosso, Marco Domaneschi, Lucia Faravelli, Jan Holnicki‐Szulc, Hans Irschik, Michael Krommer, Marco Lepidi, Alessandro Martelli, Baki Ozturk, Francesc Pozo, Gisela Pujol, Zoran Rakicevic, Jose Rodellar
      Pages: n/a - n/a
      Abstract: Structural control has been comprehensively studied over the world as a multidisciplinary research field. The present work is motivated by an attempt to give a common frame to the recent research and applications of structural control technology in civil engineering across Europe. They include novel passive dampers, functional materials and semi‐active dampers, active control systems, and their performance investigations. Design methods for the vibrations reduction of buildings, bridges, and wind turbines are discussed with reference to case studies. Control algorithms and dimension reduction techniques are also studied. Adaptation strategies and techniques based on the potential offered by piezoelectricity are reviewed. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-03-12T03:01:55.404064-05:
      DOI: 10.1002/stc.1652
       
  • Crack detection and characterization techniques—An overview
    • Authors: Yao Yao; Shue‐Ting Ellen Tung, Branko Glisic
      Pages: n/a - n/a
      Abstract: Crack occurrence and propagation are among critical factors that affect the performance and lifespan of civil infrastructures such as bridges, pipelines, and so on. As a consequence, numerous crack detection and characterization techniques have been researched and developed in the past decades in the areas of SHM and non‐destructive evaluation (NDE). The significant amount of performed studies and the large number of publications give rise to the need to systematize, condensate, and summarize this enormous effort. The aims of this paper are to summarize the knowledge about cracking and its sources, review both existing and emerging methods for crack detection and characterization, and identify the advantages and challenges for these methods. In general, this paper identifies two sensing approaches (direct and indirect) and two data analysis approaches (model‐based and model‐free or data‐driven) along with a range of associated technologies. The advantages and challenges of each approach and technology are discussed and summarized, and the future research needs are identified. This paper is intended to serve as a reference for researchers who are interested in crack detection and characterization as well as for those who are generally interested in SHM and NDE. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-03-11T00:15:34.939535-05:
      DOI: 10.1002/stc.1655
       
  • Optimal sensor placement in timber structures by means of a
           multi‐scale approach with material uncertainty
    • Authors: R. Castro‐Triguero; E. I. Saavedra Flores, F. A. DiazDelaO, M. I. Friswell, R. Gallego
      Pages: n/a - n/a
      Abstract: This paper investigates the optimal location of sensors in a timber structure when parametric uncertainty is considered in the microstructure of the material. In order to describe the proposed methodology, a timber beam is chosen for our numerical simulations. A classical sensor location methodology based on the Fisher information matrix is employed. Within a finite element framework, a homogenization‐based multi‐scale approach is adopted to model the constitutive response of timber, along with stochastic properties in the definition of the material. Nevertheless, by considering uncertainty in the micromechanical properties of wood, a significant computational cost is added to the solution of a large set of realizations represented by expensive multi‐scale analyses. In order to tackle this high cost, we build a statistical approximation to the output of the computer model, known as a Bayesian emulator. Following this strategy, three micromechanical parameters are chosen to study their influence on the selection of different configurations of sensor placement. The optimal location of sensors is assessed with three different criteria: the Fisher matrix determinant, the modal assurance criterion error and the condition number. Furthermore, the robustness of this configuration is investigated in the presence of noise. Copyright © 2014 John Wiley & Sons, Ltd.
      PubDate: 2014-03-06T02:06:47.3608-05:00
      DOI: 10.1002/stc.1654
       
 
 
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