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  Subjects -> ENERGY (Total: 294 journals)
    - ENERGY (182 journals)
    - ENERGY: GENERAL (8 journals)
    - NUCLEAR ENERGY (25 journals)
    - PETROLEUM AND GAS (52 journals)
    - RENEWABLE ENERGY (27 journals)

ENERGY (182 journals)                 | Last

Showing 1 - 200 of 406 Journals sorted alphabetically
ActaEnergetica     Open Access  
Advances in Building Energy Research     Hybrid Journal   (Followers: 9)
Advances in Energy and Power     Open Access   (Followers: 5)
Advances in High Energy Physics     Open Access   (Followers: 13)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 11)
American Journal of Energy Research     Open Access   (Followers: 8)
Annals of Nuclear Energy     Hybrid Journal   (Followers: 6)
Annual Reports on NMR Spectroscopy     Full-text available via subscription   (Followers: 2)
Annual Review of Resource Economics     Full-text available via subscription   (Followers: 10)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Solar Energy     Hybrid Journal   (Followers: 15)
Archives of Thermodynamics     Open Access   (Followers: 3)
Artificial Photosynthesis     Open Access  
Asian Bulletin of Energy Economics and Technology     Open Access   (Followers: 2)
Atomic Energy     Hybrid Journal   (Followers: 4)
Atoms for Peace: an International Journal     Hybrid Journal   (Followers: 4)
Batteries     Open Access   (Followers: 1)
Biofuel Research Journal     Open Access   (Followers: 3)
Biofuels     Hybrid Journal   (Followers: 10)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 8)
Bulletin de droit nucleaire     Full-text available via subscription   (Followers: 1)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 16)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 17)
Carbon Management     Hybrid Journal   (Followers: 6)
Catalysis for Sustainable Energy     Open Access   (Followers: 4)
CERN courier. International journal of high energy physics     Free   (Followers: 5)
Chain Reaction     Full-text available via subscription   (Followers: 1)
Clefs CEA     Full-text available via subscription   (Followers: 1)
Computational Water, Energy, and Environmental Engineering     Open Access   (Followers: 4)
Dams and Reservoirs     Hybrid Journal   (Followers: 3)
Development of Energy Science     Open Access   (Followers: 5)
Distributed Generation & Alternative Energy Journal     Hybrid Journal   (Followers: 3)
E3S Web of Conferences     Open Access  
Economics and Policy of Energy and the Environment     Full-text available via subscription   (Followers: 6)
Electrical and Power Engineering Frontier     Open Access   (Followers: 17)
Electricity Journal     Partially Free   (Followers: 1)
ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations     Open Access  
Energy     Partially Free   (Followers: 23)
Energy & Fuels     Full-text available via subscription   (Followers: 23)
Energy and Buildings     Hybrid Journal   (Followers: 7)
Energy and Emission Control Technologies     Open Access   (Followers: 3)
Energy and Environment Focus     Free   (Followers: 4)
Energy and Environment Research     Open Access   (Followers: 12)
Energy and Environmental Engineering     Open Access   (Followers: 5)
Energy and Power     Open Access   (Followers: 9)
Energy and Power Engineering     Open Access   (Followers: 14)
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: 3)
Energy Journal The     Full-text available via subscription   (Followers: 4)
Energy Law Journal     Full-text available via subscription   (Followers: 4)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 17)
Energy Policy     Partially Free   (Followers: 56)
Energy Prices and Taxes     Full-text available via subscription   (Followers: 5)
Energy Procedia     Open Access   (Followers: 2)
Energy Reports     Open Access   (Followers: 3)
Energy Research & Social Science     Full-text available via subscription   (Followers: 1)
Energy Science & Engineering     Open Access   (Followers: 4)
Energy Science and Technology     Open Access   (Followers: 14)
Energy Strategy Reviews     Partially Free   (Followers: 9)
Energy Studies Review     Open Access   (Followers: 5)
Energy Systems     Hybrid Journal   (Followers: 13)
Energy Technology     Partially Free   (Followers: 4)
Energy Technology & Policy     Open Access   (Followers: 1)
Energy, Sustainability and Society     Open Access   (Followers: 16)
Environmental Progress & Sustainable Energy     Hybrid Journal   (Followers: 5)
EPJ Photovoltaics     Open Access   (Followers: 3)
Facta Universitatis, Series : Electronics and Energetics     Open Access  
Frontiers in Energy     Hybrid Journal   (Followers: 4)
Frontiers in Energy Research     Open Access   (Followers: 2)
Fuel and Energy Abstracts     Full-text available via subscription   (Followers: 4)
Functional Materials Letters     Hybrid Journal   (Followers: 1)
Gcb Bioenergy     Open Access   (Followers: 2)
Geothermal Energy     Open Access   (Followers: 1)
GeoWorld     Full-text available via subscription   (Followers: 2)
Green     Hybrid Journal   (Followers: 2)
IEA Electricity Information     Full-text available via subscription   (Followers: 2)
IEA Natural Gas Information     Full-text available via subscription   (Followers: 2)
IEEE Power and Energy     Full-text available via subscription   (Followers: 20)
IEEE Transactions on Energy Conversion     Hybrid Journal   (Followers: 10)
IEEE Transactions on Nuclear Science     Hybrid Journal   (Followers: 7)
IEEE Transactions on Power Systems     Hybrid Journal   (Followers: 19)
IET Power Electronics     Hybrid Journal   (Followers: 17)
IngenierĂ­a EnergĂ©tica     Open Access  
Innovations : Technology, Governance, Globalization     Hybrid Journal   (Followers: 5)
International Journal of Alternative Propulsion     Hybrid Journal   (Followers: 3)
International Journal of Ambient Energy     Hybrid Journal   (Followers: 1)
International Journal of Applied Power Engineering     Open Access   (Followers: 4)
International Journal of Clean Coal and Energy     Open Access   (Followers: 5)
International Journal of Coal Science & Technology     Open Access   (Followers: 1)
International Journal of Critical Infrastructure Protection     Hybrid Journal   (Followers: 5)
International Journal of Electric and Hybrid Vehicles     Hybrid Journal   (Followers: 8)
International Journal of Emerging Electric Power Systems     Hybrid Journal   (Followers: 3)
International Journal of Emerging Multidisciplinary Fluid Sciences     Full-text available via subscription  
International Journal of Energy and Environmental Engineering     Open Access   (Followers: 3)
International Journal of Energy and Power     Open Access   (Followers: 9)
International Journal of Energy and Statistics     Hybrid Journal  
International Journal of Energy Engineering     Open Access   (Followers: 8)
International Journal of Energy Research     Hybrid Journal   (Followers: 8)
International Journal of Energy Science     Open Access   (Followers: 1)
International Journal of Flow Control     Full-text available via subscription   (Followers: 3)
International Journal of Global Energy Issues     Hybrid Journal   (Followers: 7)
International Journal of Green Energy     Hybrid Journal   (Followers: 9)
International Journal of Hydrogen Energy     Partially Free   (Followers: 12)
International Journal of Marine Energy     Full-text available via subscription   (Followers: 1)
International Journal of Nuclear Desalination     Hybrid Journal  
International Journal of Nuclear Energy Science and Technology     Hybrid Journal   (Followers: 2)
International Journal of Nuclear Governance, Economy and Ecology     Hybrid Journal   (Followers: 1)
International Journal of Nuclear Hydrogen Production and Applications     Hybrid Journal   (Followers: 1)
International Journal of Nuclear Knowledge Management     Hybrid Journal   (Followers: 1)
International Journal of Power and Energy Conversion     Hybrid Journal   (Followers: 2)
International Journal of Sustainable Energy     Hybrid Journal   (Followers: 12)
International Journal of Sustainable Energy Planning and Management     Open Access   (Followers: 2)
International Journal of Sustainable Engineering     Hybrid Journal   (Followers: 7)
International Journal of Thermodynamics     Open Access   (Followers: 4)
Journal of Alternate Energy Sources & Technologies     Full-text available via subscription  
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 5)
Journal of China Coal Society     Open Access  
Journal of Energy     Open Access   (Followers: 1)
Journal of Energy & Natural Resources Law     Hybrid Journal  
Journal of Energy in Southern Africa     Open Access   (Followers: 1)
Journal of Energy Technologies and Policy     Open Access   (Followers: 5)
Journal of Energy, Environment & Carbon Credits     Full-text available via subscription   (Followers: 2)
Journal of Fusion Energy     Hybrid Journal   (Followers: 2)
Journal of International Energy Policy     Open Access   (Followers: 3)
Journal of Magnetic Resonance     Hybrid Journal   (Followers: 10)
Journal of Modern Power Systems and Clean Energy     Open Access   (Followers: 7)
Journal of Nano Energy and Power Research     Full-text available via subscription   (Followers: 4)
Journal of Natural Resources Policy Research     Hybrid Journal   (Followers: 13)
Journal of Nuclear Energy Science & Power Generation Technology     Hybrid Journal  
Journal of Ocean Engineering and Marine Energy     Hybrid Journal   (Followers: 1)
Journal of Physical Chemistry C     Full-text available via subscription   (Followers: 25)
Journal of Power Electronics & Power Systems     Full-text available via subscription   (Followers: 6)
Journal of Radiological Protection     Full-text available via subscription   (Followers: 4)
Journal of Renewable Energy     Open Access   (Followers: 2)
Journal of Semiconductors     Full-text available via subscription   (Followers: 2)
Journal of Solar Energy     Open Access   (Followers: 7)
Journal of Solar Energy Engineering     Full-text available via subscription   (Followers: 16)
Journal of Sustainable Bioenergy Systems     Full-text available via subscription   (Followers: 1)
Journal of Sustainable Energy Engineering     Full-text available via subscription  
Journal of Technology Innovations in Renewable Energy     Hybrid Journal  
Materials for Renewable and Sustainable Energy     Open Access   (Followers: 8)
MRS Energy & Sustainability - A Review Journal     Full-text available via subscription  
Natural Resources     Open Access   (Followers: 2)
Nature Energy     Hybrid Journal   (Followers: 2)
Nigerian Journal of Technological Research     Full-text available via subscription  
Nuclear Data Sheets     Full-text available via subscription  
Nuclear Engineering and Design     Hybrid Journal   (Followers: 9)
Nuclear Law Bulletin     Full-text available via subscription   (Followers: 2)
Nuclear Materials and Energy     Open Access   (Followers: 1)
Oil and Gas Journal     Full-text available via subscription   (Followers: 9)
Oil, Gas, Coal and Electricity - Quarterly Statistics - Electricite, charbon, gaz et petrole - Statistiques trimestrielles     Full-text available via subscription   (Followers: 8)
Open Journal of Energy Efficiency     Open Access   (Followers: 2)
Power Technology and Engineering     Hybrid Journal   (Followers: 2)
Proceedings of the Institution of Civil Engineers - Energy     Hybrid Journal   (Followers: 3)
Progress in Nuclear Energy     Hybrid Journal  
Radiochimica Acta     Hybrid Journal   (Followers: 4)
Radioprotection     Hybrid Journal   (Followers: 1)
Science and Technology of Nuclear Installations     Open Access   (Followers: 1)
Smart Grid and Renewable Energy     Open Access   (Followers: 8)
Solar Energy     Hybrid Journal   (Followers: 18)
Solar Energy Materials and Solar Cells     Hybrid Journal   (Followers: 27)
SourceOCDE Energie nucleaire     Full-text available via subscription  
SourceOECD Nuclear Energy     Full-text available via subscription   (Followers: 1)
South Pacific Journal of Natural and Applied Sciences     Hybrid Journal  
Strategic Planning for Energy and the Environment     Hybrid Journal   (Followers: 4)
Structural Control and Health Monitoring     Hybrid Journal   (Followers: 6)
Surface Science Reports     Full-text available via subscription   (Followers: 14)
Sustainable Energy     Open Access  
Sustainable Energy Technologies and Assessments     Full-text available via subscription  
Sustainable Energy, Grids and Networks     Hybrid Journal  
Technology Audit and Production Reserves     Open Access  
The International Journal of Ocean and Climate Systems     Full-text available via subscription   (Followers: 6)
The Journal of Computational Multiphase Flows     Full-text available via subscription  
Universal Journal of Applied Science     Open Access  
Washington and Lee Journal of Energy, Climate, and the Environment     Open Access   (Followers: 3)
Waste Management     Hybrid Journal   (Followers: 11)
Water International     Hybrid Journal   (Followers: 10)
Wiley Interdisciplinary Reviews : Energy and Environment     Hybrid Journal   (Followers: 4)
Wind Energy     Hybrid Journal   (Followers: 2)
Wind Engineering     Full-text available via subscription   (Followers: 2)
Wireless Power Transfer     Full-text available via subscription  

       | Last

Journal Cover Structural Control and Health Monitoring
  [SJR: 1.351]   [H-I: 26]   [6 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1545-2255 - ISSN (Online) 1545-2263
   Published by John Wiley and Sons Homepage  [1598 journals]
  • Experimental investigation of the re‐centring capability of curved
           surface sliders
    • Authors: Virginio Quaglini; Emanuele Gandelli, Paolo Dubini
      Abstract: The re‐centring capability is recognized as a fundamental function of the isolation system, because it is intended to prevent substantial permanent deformation at the end of the earthquake that may affect the serviceability of the structure and eventually limit the capability of the isolators to withstand aftershocks and future earthquakes. In this study, the re‐centring behaviour of isolation systems composed of sliding bearings with curved surfaces is investigated in shake‐table tests carried out on a one‐storey steel frame with rectangular plan, scaled at one third‐length scale and isolated with four bearings. The coefficient of friction of the bearings is varied by changing the material or lubrication condition of the pads, providing different equivalent damping ratios to the isolation system. The response of the base isolated structure to selected natural ground motion waveforms is assessed in terms of the residual displacement after a single event and the accrual of displacements during a sequence of quakes, and considerations on the influence of the coefficient of friction on the re‐centring behaviour, as well as on the effect of an initial displacement offset are drawn. The re‐centring provision of the current European design code is eventually checked against the experimental data. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-04-29T02:05:53.820196-05:
      DOI: 10.1002/stc.1870
       
  • Driving effects of vehicle‐induced vibration on long‐span
           suspension bridges
    • Authors: Yang Liu; Xuan Kong, C.S. Cai, Da Wang
      Abstract: Vehicle‐induced vibration is important to consider in assessing the structural safety of bridges. This issue has been widely investigated in recent years in the open literature. The current research studies mainly emphasize the effects of bridge span and vehicle; however, the driving effects, such as the driving speed, vehicle model parameters, and driving conditions, have rarely been investigated. In this study, researches on the driving effects of vehicle‐induced vibration on long‐span suspension bridges were conducted. First, a typical three‐dimensional vehicle model with multi‐axils was proposed, and three different road roughness models rated as excellent, good, and normal were generated with a power spectral density, and a random traffic flow with 16 vehicle types was simulated using the proposed random traffic flows model generation program. Next, an effective finite element model with Ishikawa beams stiffening girder was established to investigate the driving effects of the vehicle‐induced vibration. The calculations of the effects on the vehicle body parameters, road roughness, driving direction, and speed were performed. Possible reasons for the driving effects of vehicle‐induced vibration on long‐span suspension bridges were also discussed. In addition, conclusions and recommendations for future bridge analysis and design were provided based on the results of the study. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-04-26T01:30:53.788696-05:
      DOI: 10.1002/stc.1873
       
  • Effect of different steel‐reinforced elastomeric isolators on the
           seismic fragility of a highway bridge
    • Authors: Farshad Hedayati Dezfuli; M. Shahria Alam
      Abstract: Seismic fragility assessment of highway bridges is a technique to predict the probability of the structure reaching a certain level of damage under a given seismic excitation. Vulnerable structural components have significant contributions to the failure probability of a bridge system. The effect of elastomeric isolators on the seismic fragility of highway bridges has been discussed in the literature; however, the impact of different types of rubber bearings, including natural rubber bearing, high‐damping rubber bearing, and lead rubber bearing has not been investigated yet. The objective of this study is to address this problem in detail. Seismic fragility of isolated bridges is analytically estimated by considering pier and isolation system as two major vulnerable components. Results showed that the isolation system is more fragile than the bridge pier. This finding represents those scenarios where the structure (and especially its seismic isolation system) is designed only according to the usually adopted probabilistic seismic hazard assessment, with a frequently insufficiently too short useful life. The bridge isolated by natural rubber bearing, which has the lowest lateral stiffness and energy dissipation capacity among considered bearings, is the most vulnerable system, and the bridge quipped with HDRB has the minimum risk to undergo damage. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-04-20T00:55:53.801823-05:
      DOI: 10.1002/stc.1866
       
  • Pipe dampers as passive devices for seismic control of isolated bridges
    • Authors: Saeed Mahjoubi; Shervin Maleki
      Abstract: During an earthquake, pounding of bridge superstructure into abutments is potentially destructive to structural elements and may cause unseating failure and collapse. By using energy dissipative devices such as passive dampers, the harmful pounding force may be prevented. One of the most economical passive dampers for structural applications is the pipe damper, recently introduced by the authors. In this paper, computer models of a two‐span 60‐m long conventional overpass bridge are equipped with different lengths of two types of pipe dampers, namely the dual‐pipe (DPD) and infilled‐pipe (IPD) dampers. A simplified lumped‐mass model for the bridge considering soil stiffness is proposed and used in the study. A connection detail for connecting pipe dampers to the plate girders is also presented. The detail ensures that pipe dampers act only in the longitudinal direction, and no moment is transferred to the girders. A parametric study is performed on pipe damper length and excitation peak acceleration. Seismic responses of the bridge model with and without pipe dampers are investigated. The results of the study prove that both types of pipe dampers are effective in eliminating pounding force and significantly reducing seismic responses of bridges at a very low cost. A simple displacement‐based procedure for design of dual‐pipe damper and infilled‐pipe damper elements to prevent deck‐abutment impact in bridges with expansion joints is suggested in this study. An example of the suggested design procedure is then presented. The design example demonstrates an acceptable correspondence with the results obtained from the parametric analysis. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-04-19T03:40:54.503406-05:
      DOI: 10.1002/stc.1869
       
  • Railroad bridge monitoring using wireless smart sensors
    • Authors: F. Moreu; R. E. Kim, B. F. Spencer
      Abstract: Railroads carry more than 40% of the freight, in terms of tons per mile transported in North America. A critical portion of the railroad infrastructure is the more than 100,000 bridges, which occur, on the average, every 1.4 miles of track. Railroads have a limited budget for capital investment. Therefore, decisions on which bridges to repair/replace become critical for both safety and economy. North American railroads regularly inspected bridges to ensure safe operation that can meet transport demands, using inspection reports to decide which bridges may need maintenance, replacement, or further investigation. Current bridge inspection practices recommend observing bridge responses under live load to help assess bridge condition. However, measuring bridge responses under train loads in the field is a challenging, expensive, and complex task. This research explores the potential of using wireless smart sensors (WSS) to measure bridge responses under revenue service traffic that can be used to inform bridge management decisions. Wireless strain gages installed on the rail measure real‐time train loads. Wireless accelerometers and magnetic strain gages installed in the bridge measure associated bridge responses. The system is deployed and validated on a double‐track steel truss bridge on the south side of Chicago, Illinois, owned by the Canadian National Railway. A calibrated finite element model of the bridge with known train input load estimated the responses of the bridge at arbitrary, unmeasured locations, showing the possibility of applying the system for decision making process. These results demonstrate the potential of WSS technology to assist with railroad bridge inspection and management practice. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-04-19T03:37:16.699845-05:
      DOI: 10.1002/stc.1863
       
  • Influence of high austenite stiffness of shape memory alloy on the
           response of base‐isolated benchmark building
    • Authors: Sharad Ghodke; R.S. Jangid
      Abstract: The influence of high austenite stiffness of shape memory alloy (SMA) on the response of base‐isolated benchmark building has been investigated. Dynamic analysis was performed by solving the governing equations of motion using Newmark‐beta method under three near‐fault earthquake motions. The super‐elastic behavior of SMA was modeled by the Grasser–Cozzarelli model. Structural response parameters such as top‐floor acceleration, base displacement, and base shear were chosen for investigation. Three near‐fault earthquakes with bidirectional ground motions were considered. It was observed that because of high austenite stiffness of SMA, higher accelerations associated with high frequencies are transmitted to the superstructure. The isolation device with high austenite stiffness of SMA excites the higher modes of the base‐isolated structure and thus magnifies the floor accelerations. This phenomenon can be detrimental to the high‐frequency internal equipments mounted in the base‐isolated structure. On the other hand, the high austenite stiffness of SMA does not affect the base displacement and base shear of the base‐isolated structure significantly. Furthermore, the influence of high austenite stiffness of SMA is dependent on the transformation strength of SMA and flexibility of the isolator. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-04-19T03:36:48.110784-05:
      DOI: 10.1002/stc.1867
       
  • Feasibility of shape memory alloy in a tuneable mass damper to reduce
           excessive in‐service vibration
    • Abstract: The applications of shape memory alloy (SMA) in vibration reduction are benefited by its superelasticity and thermomechanical properties. This study is a part of a series of research projects focused on reduction of timber floor vibration. In this study, the feasibility of this tuneable mass damper is tested for in‐service vibration reduction. At first, the effect of temperature ranging from 11 °C to 120 °C on the dynamic characteristics of SMA was investigated under different pre‐stressed levels. At higher temperatures, the damping ratio reduces while stiffness increases, and vice versa with decreasing temperature. SMA is sensitive to temperature when the pre‐stressed level is near the phase transformation stress. Next, the analytical model of timber floor system was built and idealised as a two‐degree‐of‐freedom system. Thirdly, a series of lab tests were carried out, and a damper consisting of an SMA bar was added on a cantilever beam with different natural frequencies, which represents floor system in the model. The results show that the vibration response of the system can be significantly reduced by the damper developed in this project, when the damper has resonance with the system. The mass of the system was then changed so as to make the damper out‐of‐tuned; the damper was then retuned by cooling/heating on SMA. After retuning of the damper, the response of the system was effectively reduced, which demonstrates the effectiveness and feasibility of employing SMA in the damper system. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-04-19T03:15:50.536692-05:
      DOI: 10.1002/stc.1858
       
  • Assessment of long‐term coordinate time series using
           hydrostatic‐season‐time model for rock‐fill embankment
           dam
    • Authors: Sonja Gamse; Michael Oberguggenberger
      Abstract: The safety control of dams is based on monitoring activities and modelling of registered observations. The statistical hydrostatic‐season‐time model was originally developed and proposed for analyzing of monitoring data on concrete dams. In some later works, the model was implemented for earth‐fill embankment dams. The model admits a simultaneous estimation of hydrostatic load, temperature influences and irreversible deformations. In our study, we analyze long‐term coordinate time series of a geodetic point on the crest of a rock‐fill embankment dam. Coordinate time series are result of an adjustment of the observations in a permanent geodetic network for different epochs. An optimal model is defined using a multiple linear regression by combined process of exclusion and inclusion of individual parameters. In the process, different statistical parameters are observed. The analyses confirmed that not all parameters are significant. The most interesting and important conclusion of computations can be stated as follows: after inclusion of significant coefficients of the hydrostatic load and long‐term trend, the residual time series still expose underlying periodicities. They can be removed by inclusion of at least one parameter of the seasonal term, where the temperature influences (i.e. air, water and soil) are modelled. The influences of the temperature on the dam are not significant in any direction, but the inclusion of the parameters improves the statistical performance of the used model. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-04-06T00:17:35.493541-05:
      DOI: 10.1002/stc.1859
       
  • Introduction of the convex friction system (CFS) for seismic isolation
    • Abstract: This work introduces an innovative seismic isolation system named the convex friction system (CFS). This newly introduced isolation system has a sliding concavity with a circular cone‐type surface, and exhibits some distinct features compared to conventional isolation techniques, such as increased uplift stability, improved self‐centring capacity, and resonance dodge when subjected to near‐fault earthquakes. A series of comprehensive analytical and numerical investigations are performed to verify these features of the CFS. First, the force–displacement relation of the CFS is established to describe the underlying philosophy of the system. The analytical model is then incorporated into numerical simulations to evaluate the seismic isolation performance of the CFS. Various ground accelerations, such as near‐fault shakings, are included in these numerical calculations. Furthermore, the numerical results are rigorously investigated to illustrate the feasibility of the CFS. Finally, the limitations of the CFS study are discussed, and conclusions are drawn. The analytical and numerical results show that the CFS performs well in seismic isolation applications. The structural response can be reduced by approximately 30% with the CFS when compared to that with the Curved Surface Slider (CSS) with a spherical‐surface concavity for some near‐fault earthquakes, which verifies the aforementioned advantages of the CFS. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-04-04T03:15:29.887194-05:
      DOI: 10.1002/stc.1861
       
  • Damage detection for shear structures based on wavelet spectral
           transmissibility matrices under nonstationary stochastic excitation
    • Authors: Jun Luo; Gang Liu, Zongming Huang
      Abstract: A new method of spectral transmissibility function extraction and damage detection for shear frame structures under nonstationary stochastic excitation is proposed. A new concept named wavelet spectral transmissibility function is proposed as damage feature. It is demonstrated that the wavelet spectral transmissibility function can characterize the structure while closing to the natural frequencies of the structure. Subsequence, the singular value decomposition of wavelet spectral transmissibility matrices with different references is proposed as an identification method of natural frequencies, and wavelet spectral transmissibility functions between two neighborhood measurement points at the natural frequencies under nonstationary stochastic excitation. At last, a new damage indicator is developed to locate and quantify the damage of shear frame structure, based on the wavelet spectral transmissibility functions and constraint linear least square method. A numerical model and a lab‐scale frame structure successfully verify the validity of the proposed algorithm. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-04-01T03:51:12.983197-05:
      DOI: 10.1002/stc.1862
       
  • Seismic performance of a damping outrigger system for tall buildings
    • Authors: Ying Zhou; Cuiqiang Zhang, Xilin Lu
      Abstract: A novel damping outrigger system is proposed for tall buildings by replacing the diagonal members with buckling restrained bracings. To investigate the conceptual design of the system, a simplified mechanical model for the outrigger system is first put forward in this paper. Four configurations of outriggers, which are commonly used in practical engineering, are compared from the aspects of stiffness, strength, and energy‐dissipating capacity. The damping outriggers of the best configuration with buckling restrained braces acting as diagonal web members of outriggers are then proposed. The effect of the system on the whole structure is demonstrated through a 632‐m‐tall building. The results indicate that the damping outrigger can serve as stiffness member under the frequently occurred earthquakes and energy dissipating member under the rarely occurred earthquakes to protect the main structure from severe damages. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-03-31T00:15:52.068766-05:
      DOI: 10.1002/stc.1864
       
  • Shape‐memory alloys as macrostrain sensors
    • Authors: Filipe Amarante dos Santos
      Abstract: The present paper studies the feasibility, through physical experimentation, of efficient and low‐cost macrostrain sensors, based on shape‐memory alloy technologies. The motivation of this work is to explore the intrinsic relation between electrical resistivity and strain, associated with the development of the stress induced martensitic transformation in superelastic shape‐memory alloys. This property enables the material to endure deformations up to 8% without any residual strains, making shape‐memory alloy wires excellent candidates for kernel elements in innovative strain transducers with dynamic ranges 4 to 5 times larger than the currently available strain transducers. An experimental prototype of a beam with a set of SMA macrostrain sensors is presented, featuring a timed scanning sequential algorithm to successfully perform the resistance readings. The aim of this work is to provide an additional insight into the potential of SMAs in new macrostrain measurement applications. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-03-30T02:40:48.657146-05:
      DOI: 10.1002/stc.1860
       
  • Reliability‐based performance optimization of TMD for vibration
           control of structures with uncertainty in parameters and excitation
    • Authors: Amit Kumar Rathi; Arunasis Chakraborty
      Abstract: Recent development of system identification using Bayesian models or stochastic filtering provides probabilistic descriptions (i.e., probability density function or statistical parameters like mean and variance) of the identified model parameters (e.g., mass, stiffness, and damping). Optimal design of passive controllers for these systems whose parameters are uncertain has remained an open problem. With this in view, the present study aims to develop numerical solution scheme for the optimal design of tuned mass damper (TMD) operating in uncertain environment. Deterministic design of TMD in these cases suffers detuning as the system parameters are random. Thus, a reliability‐based design optimization (RBDO) scheme is presented in this paper for better performance of the TMD when exposed to uncertainties. To solve the RBDO problem, response surface methodology is used along with the moving least squares technique. Dual response surfaces are used for separate handling of optimization and reliability analysis. First response surface performs optimization of the design variables of TMD, while the second response surfaces are used for the estimation of the statistical properties like mean and variance to satisfy the constrained conditions. Numerical analysis is presented to show the effectiveness of the proposed algorithm for RBDO of single degree of freedom‐TMD system as a proof of concept. The proposed meta‐model‐based algorithm can be applied for the optimal design of controller for large structures where conventional technique may face difficulty to handle both optimization and uncertainty quantification simultaneously. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-03-14T07:43:46.857224-05:
      DOI: 10.1002/stc.1857
       
  • Improved control performance of sloped rolling‐type isolation
           devices using embedded electromagnets
    • Abstract: Sloped rolling‐type isolation devices incorporating built‐in friction damping and pounding preventer have been verified to be effective for mitigation of seismic risks posed to critical equipment and facilities. Although the built‐in damping design can effectively suppress excessive displacement responses, it also increases the acceleration transmitted to the protected object above the isolation device. In this study, a novel mechanism using embedded electromagnets is proposed to improve the control performance of the isolation device. By varying the input currents to the electromagnets, the corresponding magnetic force becomes controllable and can appropriately adjust the normal force applied to the sliding interface, leading to indirect semi‐active control of friction damping force. The efficacy of the proposed mechanism is verified through several shaking table tests. Experimental results demonstrate that the control target of the isolation device can be semi‐actively achieved using the electromagnetic mechanism. Accordingly, a numerical model of such a smart isolation system, the incorporation of the proposed controllable damping mechanism into the conventional sloped rolling‐type isolation device, is proposed and calibrated by the experimental data. Its effectiveness and advantage can be clearly observed particularly when appropriate control algorithms are applied to calculating input currents for the electromagnets. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-03-09T02:05:18.872243-05:
      DOI: 10.1002/stc.1853
       
  • Robust data transmission and recovery of images by compressed sensing for
           structural health diagnosis
    • Authors: Yongchao Yang; Satish Nagarajaiah
      Abstract: Digital cameras are cost‐effective vision sensors and able to directly provide two‐dimensional information of structural condition in monitoring and assessment applications. For example, digital cameras are essential components of unmanned aerial vehicles (UAVs) and robotic agents for mobile sensing and inspection of pipelines, buildings, transportation infrastructure, etc, especially in post‐natural disaster and man‐made extreme events assessment. Additionally, while surveillance cameras have been widely used for transportation systems (e.g., traffic monitoring), if appropriately mounted on the large‐scale structures such as the bridges, they can continuously monitor the structural condition under operational loads and hazards, complementing the regular visual inspection and assessment conducted by experts. In these or other applications, efficiently and reliably transferring the structural images or videos, which are as such large‐scale, are important and challenging, especially in wireless platform that is either required (e.g., UAVs and robotic agents) or more suitable (e.g., camera monitoring networks) with only limited power and communication resources. This paper studies the computational algorithms for efficient and reliable transmission of the structural monitoring images; in particular, the compressed sensing (CS) technique is explored for robust data transmission and recovery. The sparse representation or data structure of the structural images is exploited, leading to the CS based central strategy: on some sparse domain, randomly encode large‐scale image data into few relevant coefficients, which are then transferred (robust to random data loss) and recovered (in base station) for subsequent structural health diagnosis. Image data of bench scale pipe structure, concrete structure and full scale stay cable are employed for validation of the CS based method. Its performance is also compared with traditional transform coding and low‐dimensional encoding (sampling), and their advantages and drawbacks are discussed. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-03-01T03:48:26.209965-05:
      DOI: 10.1002/stc.1856
       
  • Automated modal identification and tracking: Application to an iron arch
           bridge
    • Abstract: Challenges concerning the automation of modal identification and tracking procedures in permanent monitoring systems for Structural Health Monitoring purposes are discussed. In this context, an automated procedure based on parametric identification methods that involve the interpretation of stabilization diagrams is proposed. The methodology comprehends two key points: (i) automatic analysis of stabilization diagrams, performed through a first check of reasonable damping ratio, a subsequent modal complexity check and a final clustering of structural modes; (ii) automated tracking of the evolution in time of the identified modal properties. The proposed modal clustering and tracking steps exploit the introduction of self‐adaptable dynamic thresholds, that do not require any a priori manual tuning for the different recorded data set. Finally, the proposed approach was successfully validated using real data collected on a historic iron arch bridge. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-28T23:50:20.206439-05:
      DOI: 10.1002/stc.1854
       
  • Investigation on the fatigue performance of Ni‐Ti thin wires
    • Authors: Sara Casciati; Lucia Faravelli, Michele Vece
      Abstract: The fatigue performance of shape memory alloys is one of the main features to assess their potential in most applications (i.e., in vibration mitigation). As experimental results showed, the hysteretic properties of shape memory alloys highly depend on chemical composition, manufacturing process, and loading strain rate. In this paper, commercial wires of Nickel‐Titanium (of diameter 0.2 mm) are investigated. Specimens of different length are tested under cycles of loading‐unloading either on a shaking table or on an MTS Systems Corporation hydraulic testing apparatus (MiniBionix II). The fatigue results of the research campaign are then synthesized in an interpolating model. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-25T02:41:39.200117-05:
      DOI: 10.1002/stc.1855
       
  • Completely contactless structural health monitoring of real‐life
           structures using cameras and computer vision
    • Authors: Tung Khuc; F. Necati Catbas
      Abstract: A newly developed, completely contactless structural health monitoring system framework based on the use of regular cameras and computer vision techniques is introduced for obtaining displacements and vibrations of structures, which are critical responses for performance‐based design and evaluation of structures. To provide contactless and practical monitoring, the current vision‐based displacement measurement methods are improved by eliminating the physical target attachment. This is achieved by means of utilizing imaging key‐points as virtual targets. As a result, pixel‐based displacements of a monitored structural location are determined by using an improved detection and match key‐points algorithm, in which false matches are identified and discarded almost completely. To transform pixel‐based displacements to engineering units, a practical camera calibration method is developed because calibration standard on a physical target no longer exists. Moreover, a framework for evaluating the accuracy of vision‐based displacement measurements is established for the first time, which, in return, provides users with the most crucial information of a measurement. The proposed framework along with a conventional sensor network and a data acquisition system are applied and verified on a real‐life stadium during football games for structural assessment. The results obtained by the new method are successfully validated with the data acquired from sensors such as linear variable differential transformers and accelerometers. Because the proposed method does not require any type of sensor and target attachment, common field works such as sensor installation, wiring, maintaining conventional data acquisition systems are not required. This advantage enables an inexpensive and practical way for structural assessment, especially for real‐life structures. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-25T02:27:55.385148-05:
      DOI: 10.1002/stc.1852
       
  • Modeling and harnessing sparse and low‐rank data structure: a new
           paradigm for structural dynamics, identification, damage detection, and
           health monitoring
    • Authors: Satish Nagarajaiah; Yongchao Yang
      Abstract: This paper presents a new paradigm of explicitly modeling and harnessing the data structure to address the inverse problems in structural dynamics, identification, and data‐driven health monitoring. In particular, it is shown that the structural dynamic features and damage information, intrinsic within the structural vibration response measurement data, possesses sparse and low‐rank structure, which can be effectively modeled and processed by emerging mathematical tools such as sparse representation and compressed sensing, low‐rank matrix decomposition and completion, as well as the unsupervised multivariate blind source separation. It is also discussed that explicitly modeling and harnessing the sparse and low‐rank data structure could benefit future work in developing data‐driven approaches toward rapid, unsupervised, and effective system identification, damage detection, as well as massive SHM data sensing and management. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-23T02:24:46.491672-05:
      DOI: 10.1002/stc.1851
       
  • Rank‐revealing QR decomposition applied to damage localization in
           truss structures
    • Abstract: The purpose of this work is the development of an efficient and high‐sensitive damage localization technique for truss structures, based on the rank‐revealing QR decomposition (RRQR) of the difference‐of‐flexibility matrix. The method is an enhancement of the existing techniques of damage detection, which rely on the set of so‐called damage locating vector (DLV). The advantages of the RRQR decomposition‐based DLV (RRQR‐DLV) method are its less computational effort and high sensitivity to damage. Compared with the frequently used stochastic DLV (SDLV) method, RRQR‐DLV offers higher sensitivity to damage, which has been validated based on the presented numerical simulation. The effectiveness of the proposed RRQR‐DLV method is also illustrated with the experimental validation based on a laboratory‐scale Bailey truss bridge model. The proposed method works under ambient excitation such as traffic excitation and wind excitation; therefore, it is promising for real‐time damage monitoring of truss structures. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-18T03:16:05.874535-05:
      DOI: 10.1002/stc.1849
       
  • Monitoring bolt tightness of rail joints using axle box acceleration
           measurements
    • Abstract: Rail joints are a weak component in railway tracks because of the large impact and wheel‐rail contact forces. Every train passage contributes to the deterioration of rail joints, causing visible (e.g., battered rails) and invisible (e.g., loose bolts) damages. The invisible damage cannot be detected by the commonly performed visual inspection, which is labor intensive, unreliable, intrusive, and unsafe. In this paper, a vehicle‐borne monitoring system is used to automatically detect and assess the tightness condition of bolts at rail joints. The monitoring method is developed based on field axle box acceleration (ABA) measurements using different bolt tightness conditions. The suitability of the method is assessed by bolt tightness prediction and verification of a set of rail joints in the tram network of Sheffield, UK. The results show that ABA system can be employed to monitor bolt tightness conditions at rail joints. With this information, better planning for selective preventive maintenance actions can be taken over rail joints. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-17T02:15:44.976998-05:
      DOI: 10.1002/stc.1848
       
  • Detection of fatigue damage precursor using a nonlinear vibration approach
    • Authors: Ed Habtour; Daniel P. Cole, Jaret C. Riddick, Volker Weiss, Mark Robeson, Raman Sridharan, Abhijit Dasgupta
      Abstract: A nonlinear dynamic methodology is developed for detecting and estimating fatigue damage precursor in isotropic metal structures, prior to fatigue crack initiation, based on measurement of changes in the structure nonlinear response to harmonic base excitation. As an example, a damage precursor feature was extracted for cantilever beams by quantifying the reduction in the nonlinear stiffness because of localized microscopic material softening. The nonlinear dynamic analytical model parametrically tracks changes in the nonlinear structural stiffening as a function of the structural response and the loading cycles. Experimental results are obtained by exciting the base of cantilever beams at various amplitude levels. At high response amplitudes, the beams experience three competing simultaneous nonlinear dynamic mechanisms: (i) stiffening because of high response amplitude at the fundamental mode; (ii) softening because of inertial forces; and (iii) softening because of localized microscopic material damage caused by cyclic micro‐plasticity. The third mechanism—a potential precursor to fatigue crack initiation in the structure—resulted in a cumulative softening because of early accumulation of cyclic fatigue damage and is the focus of this study. The loading intensity and the number of cycles influenced the relative contribution of these dynamic mechanisms. Nanoindentation studies near the beam clamped boundary were conducted to confirm the fatigue degradation in the local mechanical properties as a function of loading cycles. The proposed detection method is simple to implement and detects the presence of damage precursors but lacks the resolution to discern spatial distributions of the damage intensity. Based on prior knowledge of the structural dynamic characteristics of the beam and using the proposed methodology, damage level and stiffness reduction can be detected and estimated based on changes in the nonlinear structural response. The nonlinear stiffness term in the equation of motion is found to be very sensitive to the proposed fatigue damage precursor, making it an effective method for monitoring structural degradation prior to crack developments. The proposed methodology provides new insights and constitutes a significant step toward the development of new inspection techniques. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-16T04:56:01.343704-05:
      DOI: 10.1002/stc.1844
       
  • Aeroelastic control of long‐span suspension bridges with
           controllable winglets
    • Authors: Konstantinos Nikolaos Bakis; Matteo Massaro, Martin S. Williams, David J. N. Limebeer
      Abstract: The structural‐aerodynamic modelling and dynamic stabilization of a three‐dimensional suspension bridge model is considered. Our emphasis is on investigating the effectiveness of leading and trailing edge flaps in suppressing aeroelastic instabilities. The East Great Belt Bridge is chosen as a design example, and its aeroelastic limits are computed using both thin aerofoil theory and flutter derivatives. The problem is cast in an efficient reduced size finite element formulation with aerodynamic forces expressed in the Laplace domain by use of a high‐fidelity rational function approximation. Circulatory aerodynamic forces are modelled using a feedback loop for every element, and the problem is expressed in a form suitable for implementation of modern control techniques. The structure's full multimodal response is considered, and numerical predictions show very good agreement against experimental data from the literature. In order to account for modelling errors and uncertainties while designing the controller, elements from robust control theory are invoked. The stability and robustness of the bridge when fitted with flaps controlled by optimal and suboptimal H∞ controllers are discussed for varying lengths of control surfaces along the suspended span as the optimum configuration for aerodynamic performance is investigated. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-15T02:02:29.874453-05:
      DOI: 10.1002/stc.1839
       
  • Target‐free approach for vision‐based structural system
           identification using consumer‐grade cameras
    • Abstract: Recent reports on America's infrastructure have emphasized the importance of structural health monitoring of civil infrastructures. System identification is a key component of many structural health monitoring strategies. Current system identification methods estimate models of a structure by measuring displacements, accelerations, and strains with wired or wireless sensors. However, these methods typically involve installation of a limited number of sensors at discrete locations and require additional data acquisition devices. To overcome these limitations, computer vision‐based techniques have been introduced recently that employ high‐speed and high‐resolution cameras. Such cameras can be quite costly and require tedious installation of targets. This paper investigates the potential of using consumer‐grade cameras for structural system identification without the need to install targets. The underlying methods for target‐free displacement measurements are introduced, including region of interest selection, feature detection, point tracking, and outlier removal. A set of experiments are conducted to assess the efficacy of the proposed approach by comparing the accuracy of the identified model with one obtained using a conventional wired system. Careful comparison of the results demonstrates the significant potential of the proposed approach. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-11T04:00:20.046955-05:
      DOI: 10.1002/stc.1850
       
  • Integrating sensing elements on external fixators for healing assessment
           of fractured femur
    • Authors: W. H. Ong; W. K. Chiu, M. Russ, Z. K. Chiu
      Abstract: This paper highlights the potential of integrating SHM concepts into an external fixator with the aim of using it to assess the healing of a fractured femur. A finite element analysis was first performed on the fixated femur to understand the response of the fixated femur in its fractured and healed state. The underlying mechanics will be used to establish a suitable monitoring strategy for assessment of healing. The results will be supported by a series of experiments using a fixated saw‐bone femur, which has been cut to simulate fracture. The cut was filled with epoxy, and the curing of this epoxy was used to simulate healing of the fractured region. The findings lead to an actuation and sensing protocol able to determine the state of union of a fixated long bone. This methodology was tested further by using modelling clay to approximate the mass added by soft tissue surrounding the bone. These results illustrate that the integration of SHM and orthopaedic concepts can provide a quantitative measure that can be used in conjunction with existing techniques for the monitoring of the state of healing of the fracture. This represents a significant potential of reducing or eliminating the qualitative healing assessment. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-11T03:57:15.892639-05:
      DOI: 10.1002/stc.1843
       
  • Structural health monitoring of Shanghai Tower during different stages
           using a Bayesian approach
    • Authors: F. L. Zhang; H. B. Xiong, W. X. Shi, X. Ou
      Abstract: The dynamic characterization of structures is essential for assessing their response when subjected to dynamic loads in structural health monitoring. It mainly comprises the modal parameters, that is, the natural frequencies, damping ratios and mode shapes. These modal properties are attracting more attention when structures are under construction or operation for the researchers, structure owner and engineers. This paper presents the work on the operational modal analysis of a super tall building‐the Shanghai Tower with a height of 632 m situated in Shanghai, China. A recently developed fast Bayesian method is utilized to perform modal identification, providing an effective means to identify the modal properties and assess their accuracy. In this study, ambient vibration tests are implemented in different construction stages. The corresponding modal properties and their associated uncertainties are identified and investigated, with interesting trends observed. Finite element models are also established to obtain the modal parameters in different stages and compared with the identified results. After the main structure is completed, a field test covering the eight corners of the core wall in a typical floor is performed to investigate the mode shapes. Afterward, a 12‐h measurement is performed with the information of temperature and humidity recorded simultaneously. The variation of modal properties with changing environment is studied. The results obtained will be beneficial for understanding the modal properties of this super tall building and provide a baseline for future structural health monitoring. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-11T03:28:12.284676-05:
      DOI: 10.1002/stc.1840
       
  • Free‐edge sensor placement for identifying vibration modes of
           structures subjected to impact loadings using fiber Bragg gratings
    • Abstract: For modal testing, active vibration control, or structural health monitoring, determination of sensing locations becomes a crucial issue once the interesting mode has nodal lines on which the sensors are bonded. Theoretically, only nodal points but not nodal lines would exist along free edges of the structures. Thus, measurements of vibrations along free edges of structures would maximize the number of detecting (i.e., for monitoring application) or observing (i.e., for active control application) modes. However, conventional sensors such as strain gauges or accelerometers can only be bonded on flat or smooth surfaces. In this work, fiber Bragg gratings, which possess linear geometric shape, are employed to investigate the feasibility of detecting more vibration modes along free edges of structures. A traction‐free aluminum solid with symmetric geometry subjected to various impact loadings is considered. To verify the capability of the free‐edge bonded FBG sensors for detecting vibration modes from impact‐induced responses, relationships between sensing locations, impact locations, and intensities of modes, are discussed with the aid of mode shapes obtained by the finite element me\thod. Within frequencies up to 30 kHz, 14 out‐of‐plane dominated and 25 in‐plane dominated modes in frequency domain are examined. Multiple modes, that is, repeated roots, two or more modes with identical frequencies due to symmetric geometry, are also analyzed. Our experimental results show that placing the FBGs along free edges of structures to acquire and analyze more vibration modes is feasible. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-09T02:06:45.133003-05:
      DOI: 10.1002/stc.1842
       
  • Sparse feedback structures for control of civil systems
    • Authors: Reuben D. Verdoljak; Lauren E. Linderman
      Abstract: Modern structural control systems use centralized, wired sensor feedback to impart counter forces based on measurement of the response. However, centralized systems can be sensitive to sensor failure, controller failure, and the reliability of sensor links. The recent study of wireless control systems has encouraged decentralized control approaches to overcome wireless structural control challenges, including limiting the wireless communication required and the associated slow sampling rate and time delays in the control system. Decentralized control offers the additional advantages of multiple independent controllers and small subsets of measurement feedback. Previous decentralized structural control algorithms, both Ad‐Hoc and Heuristic, enforce a spatial sparsity pattern during the design, which is assumed a priori. Therefore, the optimal feedback structure is not considered in the design. This work explores a decentralized optimal LQR design algorithm where the sparsity of the feedback gain is incorporated into the objective function. The control approach is compared with previous decentralized control techniques on 5‐ and 20‐story control benchmark structures fitted with active or semi‐active systems. Additionally, the sparsity and control requirements are compared with centralized designs to gain insight on the overall performance of sparse feedback systems. The optimal sparse feedback design offers the best balance of performance, measurement feedback, and control effort. Additionally, the feedback structure identified is not easily identifiable a priori in the reduced order model of the 20‐story structure, highlighting the significance of particular measurements in this feedback framework. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-05T01:30:33.95774-05:0
      DOI: 10.1002/stc.1847
       
  • Finite element model updating using strain‐based power spectral
           density for damage detection
    • Authors: Masoud Pedram; Akbar Esfandiari, Mohammad Reza Khedmati
      Abstract: In this paper a new sensitivity‐based finite element (FE) model updating method using spectral density of strain as metric is introduced, which is applicable for damage detection and structural health monitoring purposes. Derivation of the sensitivity equation is exact without any need for approximation. A set of incompletely measured natural frequencies and damping loss factors of the damaged structure is used to deal with incomplete measurement without implementation of the FE model reduction or data expansion algorithms. The insights provided from the distribution of the spectral strain energy among the elements in the intact model are used for selection of excitation location. The solution to the developed sensitivity equation is achieved by linear least square and imposing unprejudiced side constraints on the design variables. The proposed method is successfully examined on the FE model of a 3D truss and frame structure and is capable of localization and quantification of damage. The method is robust against measurement, natural frequency, and mass modeling error. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-04T03:47:43.57698-05:0
      DOI: 10.1002/stc.1833
       
  • A novel approach to the optimum design of MTMDs under seismic excitations
    • Abstract: This paper presents an efficient single‐stage scheme for the global optimization of multiple tuned mass dampers subjected to seismic excitations. To take into account the oscillators' vertical and horizontal distribution, the use of the ground structure concept is proposed. This procedure is very useful because it avoids the pre‐definition of the tuned mass dampers number and their placement. Because the multiple tuned mass dampers optimization problem is nonconvex and multimodal, this paper presents a novel hybrid stochastic/deterministic algorithm. The Firefly algorithm is used in the stochastic part, that is, to locate the global solution region and to provide a starting point to the local optimizer. The Nelder–Mead algorithm is then used as a local optimizer. Global search restarts are applied after convergence of the local search, allowing convergence to the global solution. In addition, because the structural response is obtained in the frequency domain, the scheme becomes very robust and requires considerably less computational effort than time history analysis. For illustration purposes, a numerical example on a ten‐story shear building is demonstrated. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-02T04:18:24.283126-05:
      DOI: 10.1002/stc.1845
       
  • A mode shape‐based damage detection approach using laser measurement
           from a vehicle crossing a simply supported bridge
    • Authors: Eugene J. OBrien; Abdollah Malekjafarian
      Abstract: This paper presents a novel algorithm for bridge damage detection based on the mode shapes estimated from a passing vehicle. The bridge response at the moving coordinate is measured from an instrumented vehicle with laser vibrometers and accelerometers. A modified version of the Short Time Frequency Domain Decomposition method is applied to the measured responses. The bridge mode shape is estimated with high resolution, which is appropriate for damage detection. A damage index based on mode shape squares is used to detect the presence and location of the damage. A numerical case study of a half‐car model passing over a bridge is described in this paper, which validates the performance of the proposed approach. Several damage scenarios are considered including different locations and severities. It is shown that the presence and location of the damage can be detected with acceptable accuracy when the vehicle is moving very slowly. In addition, the performance of the method using higher vehicle speeds is investigated and shows that the approach works well for speeds up to 8 m/s. The sensitivity of the algorithm to measurement noise is also studied by adding several levels of noise to the responses measured on the vehicle. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-02T03:40:11.514044-05:
      DOI: 10.1002/stc.1841
       
  • Extended discrete‐time transfer matrix approach to modeling and
           decentralized control of lattice‐based structures
    • Abstract: This paper presents the modeling and control of an aircraft wing structure constructed by lattice‐based cellular materials/components. A novel model reduction process is proposed that utilizes the extended discrete‐time transfer matrix method (E‐DT‐TMM). Through recursive application of the E‐DT‐TMM, an effective reduced‐order model can be obtained in which a decentralized discrete‐time linear quadratic regulator (LQR) controller can be designed. To demonstrate the efficiency of the proposed concept, a prototype wing structure is studied. The analysis and simulation results show that the performance of the proposed E‐DT‐TMM based decentralized LQR controller is comparable with that of the full‐state continuous LQR controller. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-01T03:03:07.159144-05:
      DOI: 10.1002/stc.1837
       
  • An analysis of pounding mitigation and stress waves in highway bridges
           
    • Authors: Suchao Li; Anxin Guo, Hui Li, Chenxi Mao
      Abstract: Seismic‐induced pounding between adjacent structures that are insufficiently separated can cause significant structural damage, even collapse, during severe earthquakes. This paper presents an experimental and numerical investigation into mitigating pounding on highway bridges using novel shape memory alloy pseudo‐rubber shock‐absorbing devices (SMAPR‐SADs). The mechanical properties and a theoretical model of SMAPR‐SADs are briefly introduced and investigated. Next, a series of shaking table tests on a 1:30 model of a steel highway bridge are conducted to investigate the effectiveness of the SMAPR‐SADs in mitigating the pounding of the structures. Based on the experimental results, the pounding‐induced stress waves are analyzed using wave theory and the cross‐wavelet transform method. Subsequently, numerical models of highway bridges with and without SMAPR‐SADs are proposed. The pounding mitigation mechanism of SMAPR‐SADs is analyzed using the momentum theorem, their ability to dissipate energy, and stress wave absorption theory. Two indexes representing the energy absorption and dissipation abilities of SMAPR‐SADs are proposed and investigated. Finally, the effect of the axial stiffness of SMAPR‐SADs on pounding mitigation is analyzed. The experimental and theoretical results demonstrate that SMAPR‐SADs are able to absorb energy stably and can significantly reduce the pounding response of highway bridges under seismic excitations. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-01T02:49:27.51003-05:0
      DOI: 10.1002/stc.1835
       
  • Suspension‐type tuned mass dampers with varying pendulum length to
           dissipate energy
    • Abstract: In this paper, an optimal energy dissipation control algorithm is applied into a semi‐active suspension‐type tuned mass damper (SA‐STMD) to suppress excessive vibration by means of variable pendulum length. The SA‐STMD mechanism consists of a mass block, a suspension rope, and a movable fulcrum that can be a short tube driven by a linear motor to vertically move along the suspension rope. As the fulcrum goes up, the pendulum length is extended, resulting in a smaller stiffness of the SA‐STMD, and vice versa. Accordingly, the restoring force in the SA‐STMD can be adjusted by varying the fulcrum positions. In the case where the energy dissipation ability by the original STMDs is insufficient, the movable fulcrum in the SA‐STMD system can compensate the STMDs for stiffness according to the proposed optimal energy dissipation control algorithm to provide controllable restoring forces. The controllable restoring forces are designed to act as viscous dampers that can make up for the lack of energy dissipation capacity. The numerical results from the time domain and frequency domain analyses show that the proposed approach utilizing the optimal energy dissipation control algorithm to adjust the pendulum length can induce controllable restoring forces with a butterfly‐shaped hysteresis loop, supplying a sufficient energy dissipation capacity to reduce responses to the unexpectedly large external vibration. Another potential benefit is cost reduction because of use of a less number of conventional viscous dampers in the STMD system. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-02-01T02:40:46.144104-05:
      DOI: 10.1002/stc.1834
       
  • Application of stochastic subspace identification for stay cables with an
           alternative stabilization diagram and hierarchical sifting process
    • Abstract: The modal parameters of numerous modes for a stay cable are usually required in engineering practice. The application of conventional stochastic subspace identification techniques without delicate cautions, however, has been found to be unsuccessful in this case. Aiming to attack such a difficulty, this study establishes a new methodology based on the covariance type of stochastic subspace identification for extensively identifying the modal parameters of a stay cable. Several details of choosing the parameters in performing stochastic subspace identification are first discussed. An important discovery is that the lower limit for setting the time lag parameter can be decided by the ratio of the fundamental period of cable to the sampling time increment for a valid identification with the conventional stabilization diagram. Inspired by the aforementioned criterion, an alternative stabilization diagram is further proposed to more conveniently distinguish stable modal parameters of cable. A hierarchical sifting process including three stages is then developed to systematically and automatically extract reliable modal parameters from the alternative stabilization diagram. Demonstrated by analyzing the ambient vibration measurements for three stay cables of Chi‐Lu Bridge, the feasibility of this new approach is verified with successfully obtaining the modal frequencies, damping ratios, and mode shape ratios for almost all the cable modes in the examined frequency range. Another interesting finding is that the modal frequencies and damping ratios of bridge deck can also be effectively identified from the ambient vibration signals of cable. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-28T02:30:18.749401-05:
      DOI: 10.1002/stc.1836
       
  • Mode shape‐based damage detection in plate structure without
           baseline data
    • Authors: Sandris Rucevskis; Rims Janeliukstis, Pavel Akishin, Andris Chate
      Abstract: In this paper, a mode shape curvature‐based method for detection and localization of damage in plate‐like structures is described. The proposed algorithm requires only the mode shape curvature data of the damaged structure. The damage index is defined as the absolute difference between the measured curvature of the damaged structure and the smoothed polynomial representing the curvature of the healthy structure. To examine the advantages and limitations of the proposed method, several sets of numerical simulations are carried out. Simulated test cases considering different levels of damage severity, measurement noise and sensor sparsity are studied to evaluate the robustness of the method under the noisy experimental data and limited sensor data. Applicability and effectiveness of the proposed damage detection method are further demonstrated experimentally on an aluminium plate containing mill‐cut damage. The modal frequencies and the corresponding mode shapes are obtained via finite element models for numerical simulations and by using a scanning laser vibrometer for the experimental study. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-20T03:34:01.608609-05:
      DOI: 10.1002/stc.1838
       
  • Bridge related damage quantification using unmanned aerial vehicle imagery
    • Authors: A. Ellenberg; A. Kontsos, F. Moon, I. Bartoli
      Abstract: Visual inspection procedures remain the primary method of infrastructure assessment throughout the USA, but their shortcomings are numerous. In addition to their widely acknowledged variability and subjectivity, the large scale of civil infrastructure systems presents expensive access and time requirements that constrain the frequency of visual inspections and result in poor temporal resolution, which hampers effective decision‐making. To overcome this challenge, the research reported herein aimed to assess the ability of computer algorithms together with imagery collected by unmanned aerial vehicles (UAV) to extract accurate and quantitative information to help inform infrastructure management decisions. Techniques such as homography and lens distortion correction are used in this article in a post‐processing framework that allows the use of color images obtained by UAVs for actual damage quantification measurements. The experiments described in this article utilize a UAV with a mounted camera and provide measurements from a representative infrastructure mockup with several simulated damage scenarios. Deformation measurements, change detection (related to structural features and the size of deterioration), and crack pattern identification were all analyzed. The results indicated that the developed post‐processing algorithms were able to extract quantitative information from UAV captured imagery. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-20T03:27:55.397696-05:
      DOI: 10.1002/stc.1831
       
  • Structural damage detection using wireless passive sensing platform based
           on RFID technology
    • Authors: Mateusz Lisowski; Przemyslaw Gonek, Jakub Korta, Tadeusz Uhl, Wieslaw J. Staszewski
      Abstract: A wireless and battery‐free passive sensing platform is proposed for structural damage detection. The platform is based on the radio‐frequency identification (RFID) technology, where a standard RFID transponder device serves as an interface between low‐power sensors – used for damage detection – and RFID reading devices. Sensor data are transmitted remotely from this sensing platform to a Personal Computer (PC) that controls the entire system. Energy harvesting is the major novelty of the proposed approach. The magnetic field produced by an antenna of the RFID reading device is used for energy harvesting. The platform supports different types of sensors that can be positioned in remote locations and used for structural damage detection. The sensing capability and the damage detection performance of the proposed system are demonstrated using two simple application examples, that is, vibration measurements in a beam‐like structure subjected to the force excitation and temperature measurements in a bearing that supports a rotating shaft. The results illustrate the great potential of the proposed sensing platform for structural health monitoring applications, particularly in remote, difficult‐access, or hazardous conditions. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-19T21:23:20.652087-05:
      DOI: 10.1002/stc.1826
       
  • Theoretical prediction of the dynamic behavior of rolling‐ball
           rubber‐layer isolation systems
    • Authors: Alessandra Fiore; Giuseppe Carlo Marano, Maria Gabriella Natale
      Abstract: This paper presents the results of a theoretical study carried out to characterize the dynamic behavior of a seismic isolation system consisting of steel‐rolling balls on rubber layers. This type of device reduces seismic hazard during earthquakes by decoupling the superstructure from the ground motion and by dissipating the energy in damping, thanks to the viscous‐elastic properties of the rubber. The behavior of the rolling balls on rubber layers isolation system is described by achieving suitable expressions for the resultant normal and shear forces acting in the device. In particular, it is shown how the resultant shear force is highly affected by the correct definition of the slip and stick regions, which develop at the steel‐rubber contact area. The analysis allows to identify the main parameters characterizing this type of device, furnishing a valid tool in order to correctly calculate some response quantities significantly influenced by the isolation system. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-19T21:23:04.823953-05:
      DOI: 10.1002/stc.1830
       
  • Posicast control of structures using MR dampers
    • Authors: Tarek Edrees Alqado; George Nikolakopoulos
      Abstract: In this article, a novel application of a semi active posicast control scheme for structures with magneto‐rheological (MR) dampers is presented. MR dampers are considered to be highly promising of semi‐active control systems, which are becoming increasingly popular for alleviating the effects of dynamic loads on civil engineering structures because they combine the merits of both passive and active control systems. The main contribution of this article relates to the design, application, tuning and performance evaluation of the novel posicast control scheme for structural control. The efficiency of the suggested control strategy was evaluated by performing numerical simulations of a benchmark three‐storey building with an MR damper, rigidly attached between the first floor and the ground. The damper's behaviour was simulated using the Bouc–Wen model. Seven evaluation criteria were used to assess the performance of the proposed posicast control scheme in reducing the excited structure's responses to dynamic loading. The simulation's results indicated that the posicast control scheme had significant advantages over conventional alternatives in terms of performance and efficiency. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-13T03:09:56.500907-05:
      DOI: 10.1002/stc.1832
       
  • Enhanced nonlinear crack‐wave interactions for structural damage
           detection based on guided ultrasonic waves
    • Authors: Kajetan Dziedziech; Lukasz Pieczonka, Piotr Kijanka, Wieslaw J Staszewski
      Abstract: The paper presents a new damage‐detection method based on nonlinear crack‐wave interaction. Low‐frequency vibration excitation is introduced to perturb damage, and high‐frequency interrogating wave is used to detect damage‐related nonlinearities. However, in contrast to other crack‐wave interaction approaches, localised wave packets are used for high‐frequency excitation. The synchronisation of the low‐frequency vibration with the interrogating high‐frequency wave packets is a key element of the proposed method. Numerical simulations and simple experimental tests in cracked aluminium beams are performed to demonstrate the method. The results show that the proposed method can detect and localise damage‐related and intrinsic nonlinearities, allowing for reliable damage detection. The method does not require baseline measurements representing an undamaged condition, and it is not sensitive to temperature variations. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-10T22:08:34.190044-05:
      DOI: 10.1002/stc.1828
       
  • Output‐only damage detection using vehicle‐induced
           displacement response and mode shape curvature index
    • Authors: Dongming Feng; Maria Q. Feng
      Abstract: Most of the existing bridge superstructure damage detection methods are based on acceleration or strain response due to ambient excitation. This paper proposes a bridge damage detection procedure that utilizes vehicle‐induced displacement response without requiring prior knowledge about the traffic excitation and road surface roughness. This study is partially motivated by the recent advances in convenient measurement of structural displacements enabled by video‐based sensors. Vehicle–bridge interaction analysis shows that when subjected to moving vehicles, the bridge displacement response is dominated by the first‐order mode component. This justifies the proposed damage detection method that only requires the first‐order mode shape curvature. While conventionally the mode shapes are extracted based on operational modal analysis, the first‐order mode shape is extracted by directly analyzing the power spectral density functions of measured bridge displacement responses under vehicle excitations. Numerical simulations are carried out to investigate the feasibility and performance of the proposed damage detection method using three damage scenarios including damage at single, double, and multiple locations, each involving several extents of damage defined by the reduction in element stiffness. The results reveal that all the damage cases can be successfully identified. Furthermore, the damage detection performance is evaluated for cases involving different classes of road surface roughness and less measurement points. The study demonstrates the potential of the proposed model‐free and time‐efficient method for damage detection of bridge structures. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-06T00:06:16.780407-05:
      DOI: 10.1002/stc.1829
       
  • Localized genetically optimized wavelet neural network for
           semi‐active control of buildings subjected to earthquake
    • Authors: S. M. A. Hashemi; H. Haji Kazemi, A. Karamodin
      Abstract: Control algorithm is one of the most important aspects in successful control of buildings against earthquake. In recent years, because of their capabilities, soft computing methods, stemmed from human brain abilities, have become of particular interest to researchers. In this paper, a wavelet neural network‐based semi‐active control model is proposed in order to provide accurately computed input voltage to the magneto rheological dampers to generate the optimum control force of structures. This model is optimized by a localized genetic algorithm and then applied to a nine‐story benchmark structure subjected to 1.5× El Centro earthquake. The results show an average of 43% reduction of maximum drift in the controlled structure versus the uncontrolled one. The capability of the controller is also validated by applying other far‐field and near‐field earthquakes. The capability and efficiency of the proposed model are demonstrated in terms of drift, acceleration and base shear reduction. The proposed wavelet neural network is also compared with a tangent hyperbolic‐based feed forward neural network, linear quadratic Gaussian, clipped optimal controller, and genetic algorithm‐based fuzzy inference systems to show the superiority of the proposed controller. Copyright © 2016 John Wiley & Sons, Ltd.
      PubDate: 2016-01-05T23:44:08.115232-05:
      DOI: 10.1002/stc.1823
       
  • Issue Information
    • Pages: 799 - 801
      Abstract: No abstract is available for this article.
      PubDate: 2016-04-03T23:17:22.319387-05:
      DOI: 10.1002/stc.1790
       
  • On‐line unsupervised detection of early damage
    • Abstract: Structural health monitoring (SHM) strategies should ideally consist of continuous on‐line damage detection processes, which do not need to rely on the comparison of newly acquired data with baseline references, previously defined assuming that structural systems are undamaged and unchanged during a given period of time. The present paper addresses the topic of SHM and describes an original strategy for detecting damage in an early stage without relying on the definition of data references. This strategy resorts to the combination of two statistical learning methods. Neural networks were used to estimate the structural response, and clustering methods were adopted for automatically classifying the neural networks' estimation errors. To ensure an on‐line continuous process, these methods were sequentially applied in a moving windows process. The proposed original strategy was tested and validated on numerical and experimental data obtained from a cable‐stayed bridge. It proved highly robust to false detections and sensitive to early damage by detecting small stiffness reductions in single stay cables as well as the detachment of neoprene pads in anchoring devices, resorting only to a small amount of inexpensive sensors. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-12-28T04:44:07.530761-05:
      DOI: 10.1002/stc.1825
       
  • Algorithm for the analysis of deformations and stresses due to torsion in
           a metal beam from LIDAR data
    • Abstract: An interesting field for application of LIDAR technology is structural health monitoring, especially in the study of deformation and stress in the beams. In the beams, it is not only the deformation due to bending that is an issue of control but it is also important to check the deformation due to torsion, particularly in open cross sections such as I, U, L, which have a very low torsional strength. This paper presents a new algorithm for obtaining, automatically and separately, the deformations in a beam subjected to torsional and bending loading, respectively, from LIDAR data. With the values of the deformation found by the new developed algorithm, the shear stresses are obtained. The methodology presented in this paper has been tested with a real beam in a laboratory under different load situations. The results obtained from the algorithm were compared not only with measurements by direct methods but also with results obtained by FEM simulation of the 3D model of the beam. The results found by the new algorithm compare with the other methods; therefore, this verifies the validity of the method for applications of structural health monitoring of metal structures. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-12-28T04:42:02.095205-05:
      DOI: 10.1002/stc.1824
       
  • Real‐time hybrid simulation of multi‐story structures
           installed with tuned liquid damper
    • Abstract: As a low cost and maintenance energy‐absorbing device, tuned liquid damper (TLD) is being widely used to suppress structural vibration. In this paper, the real‐time hybrid simulation (RTHS) is employed to investigate the performance of TLD for controlling seismic responses of actual multi‐story structures, where the TLD is experimentally modeled as physical substructure and the multi‐story structure is numerically simulated as numerical substructure. Taking advantage of RTHS technique, a methodology for achieving full‐scale TLD experiments is developed through suitable similarity design; a new interaction force measurement method and a new dual explicit algorithm are embedded into RTHS system to enhance simulation capability. First, the seismic response of a two‐story structure installed with TLD is analyzed by applying RTHS. Correspondingly, the pure shaking table test is performed to assess the accuracy of the RTHS. Then, the effectiveness of TLD for structures with various numbers of floors and different structural properties is tested through RTHS by varying the simulation model of the numerical substructure. Finally, the effects of mass ratio and structural damping ratio on a given TLD‐structure system are investigated. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-12-22T01:35:55.73777-05:0
      DOI: 10.1002/stc.1822
       
  • Monitoring crowd load effect on typical ancient Tibetan building
    • Abstract: Tibetan heritage building has attracted attention from many people who have interest in its historical and cultural value. Many of these buildings are opened to visitors in recent years, and the live load from tourist becomes a problem with increasing number of visitors. A monitoring system has been installed in a typical ancient Tibetan timber building to collect data on the material stresses and deformations of structural components. Based on the data collected, a strategy is proposed to evaluate the component of structural response induced by crowd load. A statistical relationship is obtained between the effective temperature change and the recorded strain increment. Results show that the measured strain is closely related to the number of visitors, and this may form the basis for a method to further evaluate the safety and integrity of the structure. An experiment was conducted on a corridor of the building with random pedestrian loading to validate the proposed strategy with encouraging results. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-12-22T01:19:03.910174-05:
      DOI: 10.1002/stc.1821
       
  • Full‐scale bridge damage identification using time series analysis
           of a dense array of geophones excited by drop weight
    • Authors: Reza V. Farahani; Dayakar Penumadu
      Abstract: This paper presents a simple and inexpensive technique for damage identification of bridges using drop weight vibration data of bridges recorded by an array of geophones, highly sensitive sensors to record vibration, and time series analysis. The dynamic response of bridges obtained using drop weight as an excitation source is convolved with white noise to create suitable input for autoregressive (AR) models. A two‐stage prediction model, combined AR and autoregressive with exogenous input (ARX), is employed to obtain a damage‐sensitive feature. An outlier analysis method is developed based on the Monte Carlo simulation to identify the existence of damage. The proposed technique is verified using unique vibration data of two full‐scale steel‐girder bridges located on I‐40 through downtown Knoxville, Tennessee, and subjected to progressive damage scenarios induced to steel girders. The results of the analysis for the vertical vibration data of the test bridges indicate that the proposed technique is able to detect the damage induced on the real bridge girders consistently even when the damage level is small and damage is located near a support; however, damage is not well localized or quantified in these two highly redundant bridges. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-25T03:21:41.951305-05:
      DOI: 10.1002/stc.1820
       
  • Modeling and experimental validation of a
           multiple‐mass‐particle impact damper for controlling
           stay‐cable oscillations
    • Authors: Philipp Egger; Luca Caracoglia, Johann Kollegger
      Abstract: Impact dampers are often used in the field of civil, mechanical, and aerospace engineering for reducing structural vibrations. This research is motivated by a practical problem, that is, the reduction of wind‐induced and rain–wind‐induced vibrations in long, flexible and low‐damping stay‐cables. A new concept of distributed‐mass impact damper has been proposed, designed, fabricated, and tested experimentally at Vienna University of Technology by using a 31.2‐m actual stay. The results of the full‐scale experiments (free‐decay tests) are illustrated in this study. Because the performance of the new device was very promising, with total damping ratio three to 10 times larger than the original damping in the stay, modeling of the damper device was needed to ensure adequate practical application in the future. This study examines three different reduced‐order models, derived in an attempt to characterize the complex behavior of the new device. Verification and validation of the models are carried out by comparison with the experimental results. Finally, selection of an adequate model, based on both experiments and simulations, is described and discussed. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-12T20:39:32.554385-05:
      DOI: 10.1002/stc.1812
       
  • Multiple‐crack identification in a channel section steel beam using
           a combined response surface methodology and genetic algorithm
    • Authors: Palash Dey; S. Talukdar, D. J. Bordoloi
      Abstract: The present study outlines a sequentially integrated finite‐element method (FEM)–response surface method (RSM)–genetic algorithm (GA) framework and implements this to predict the crack parameters, namely, crack location and crack depth ratio. A central composite face centered response surface design of the RSM technique is used to establish the direct relationships between the input parameters (crack location and crack depth ratio) and responses (natural frequencies) to build the response surface function (RSF). Multiple edge cracks are considered, which exist on the top flange of a thin‐walled channel section cantilever beam and modeled as line spring elements. In order to obtain RSFs of the first five natural frequencies in terms of process factors such as crack position and crack depth ratio, a number of numerical experiments based on FEM are conducted by using the design‐of‐experiment approach. An objective function obtained as the square of the difference between RSF and experimentally measured natural frequency has been minimized using GA to find out the optimum crack parameters. Twenty‐four steel channel beam specimens have been tested in the laboratory to extract the crack parameters from measured natural frequencies using the proposed approach. The results of the study indicate that the proposed approach performs remarkably, yielding crack parameters with great precision. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-10T22:11:47.025626-05:
      DOI: 10.1002/stc.1818
       
  • Automatic mapping of moisture affectation in exposed concrete structures
           by fusing different wavelength remote sensors
    • Abstract: Water content is a critical parameter for the early detection of moisture degradation in exposed concrete structures. Traditionally, visual inspection is the most extended procedure to detect superficial pathologies caused by moisture in concrete constructions, principally when access is limited. For such cases, remote sensing is a valuable tool to recover radiometric information useful for detecting and quantifying different degrees of affectation caused by water. This paper presents an approach to identifying and evaluating the water content in a real concrete structure by fusing several sensors recording data in different wavelengths. In particular, a procedure to integrate three‐dimensional intensity data collected by two terrestrial laser scanners (Riegl‐Z390i and FARO Focus 3D) with two‐dimensional radiometric data provided by a six‐band multispectral camera and a commercial digital camera (MCA6 Tetracam and Canon EOS 5D) is developed. After data fusion in a two‐dimensional space, a multiband image was created for further spectral analysis. Finally, an unsupervised classification using clustering algorithms was performed to identify the degrees of affectation and the most suitable remote sensor for moisture mapping. Comparisons between the sensors used in this survey reveal that intensity imagery from both laser scanners has high potential for the recognition and characterisation of the degree of moisture in this type of structure. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-08T23:02:05.198576-05:
      DOI: 10.1002/stc.1814
       
  • Novel hexapod‐based unidirectional testing and FEM analysis of the
           RNC isolator
    • Authors: Mohammed Ismail
      Abstract: An innovative Stewart platform (hexapod)‐based testing rig is designed, constructed, and used herein to experimentally characterize a seismic isolation device named roll‐in‐cage (RNC) isolator. The testing rig is a result of integrating a mechanical extension, or upgrade, to the hexapod. This allows for performing up to 15 standard mechanical tests using cylinder, block, prism, beam, plate, or bar specimens, besides reduced‐scale prototypes of seismic isolation bearings. Several one‐tenth reduced‐scale prototypes of the RNC isolator are experimentally examined in this paper using this testing rig. Cyclic horizontal displacement tests are performed considering different test parameters including shear displacement amplitude, axial load, and loading frequency. The RNC isolator's force–displacement relationships, shear stiffness, and damping properties are investigated. Vertical cyclic displacements are also applied to examine the RNC isolator's capability to withstand vertical axial tension. Furthermore, tests at the ultimate level consisting of an increasing‐amplitude shear loading, beyond the bearing's design displacement limit, are also carried out to investigate the bearing's behavior after activating its inherent self‐stopping, or buffer, mechanism. The obtained experimental outputs are then related to analytical and thorough FEM simulation outputs. This relation is intended to validate those previously developed mathematical and numerical models of the RNC isolator based on the real experimental measurements in this paper. A comparative study of the results is then performed, and the main observations are highlighted. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-05T01:03:05.176122-05:
      DOI: 10.1002/stc.1817
       
  • Vision‐based multipoint displacement measurement for structural
           health monitoring
    • Authors: Dongming Feng; Maria Q. Feng
      Abstract: A novel noncontact vision sensor for simultaneous measurement of structural displacements at multiple points using one camera is developed based on two advanced template matching techniques: the upsampled cross correlation (UCC) and the orientation code matching (OCM). While existing studies on vision sensors are mostly focused on the time‐domain performance evaluation, this study investigates the performance in both time and frequency domains through a shaking table test of a three‐story frame structure, in which the displacements at all the floors are measured by using one camera to track either high‐contrast artificial targets or low‐contrast natural targets on the structural surface such as bolts and nuts. Excellent agreements are observed between the displacements measured by the single camera and those measured by high‐performance laser displacement sensors. The results of structural modal analysis based on the measurements by the vision sensor and reference accelerometers also agree well. Moreover, the identified modal parameters are used to update the finite element model of the structure, demonstrating the potential of the vision sensor for structural health monitoring applications. This study further examines the robustness of the proposed vision sensor against ill environmental conditions such as dim light, background image disturbance, and partial template occlusion, which is important for future implementation in the field. Significant advantages of the proposed vision sensor include its low cost (a single camera to remotely measure structural displacements at multiple points without installing artificial targets) and flexibility to extract structural displacements at any point from a single measurement. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-05T00:45:34.260543-05:
      DOI: 10.1002/stc.1819
       
  • Using a phase difference detection technique for monitoring the structural
           health of bridge piers
    • Abstract: In this study, a new technique for monitoring the structural health of bridge piers, from the point of view of earthquake‐induced damage, is introduced and then simulated and evaluated using a scaled model of a typical bridge. This system uses the detection of phase difference between two synchronous receiver nodes, connected through a wireless sensor network, and utilizes an array of inexpensive, high‐frequency oscillator circuits (4 GHz) as wireless transmitters, placing them at the important structural positions of the bridge piers, and then receiving and analyzing the signals sent by these transmitters to the two receiver nodes. The proposed monitoring system measures the changes in phase difference between two synchronous receiver nodes before and after damage (displacement or deformation); it shows an accuracy of a tenth of a millimeter in the simulations, and it also has high reliability in monitoring the structural heath of the bridge because it provides a real‐time report of the status of each transmitter (activated, deactivated, and damaged). The proposed system is low in price compared to other structural health monitoring (SHM) methods and also entails a much lower volume and complexity of data processing than similar techniques. This study did not carry out any field trials, but a complete simulation using an array of six transmitters (TX) and two receivers (RX) was conducted for a scaled model with six piers, and mathematical and geometrical principles and signal processing and simulation details were thoroughly examined. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-05T00:26:16.908969-05:
      DOI: 10.1002/stc.1813
       
  • Field dynamic test and Bayesian modal identification of a special
           structure – the Palms Together Dagoba
    • Abstract: The Palms Together Dagoba at Famen Temple is a 12‐story steel‐reinforced concrete building, which comprises a vertical inversion and setback tubes with two inflection points formed along its height. It contains two towers with the first two and the top two floors connected, while the remaining floors are separated forming an irregular configuration. During its construction, an earthquake of 8.0 magnitude struck about 500 km away. The seismic intensity at the site is reported to be 6, which may result in some cracks for the local structures. This paper presents the work on field test 1 month after the earthquake and modal identification of the Dagoba. To determine the dynamic characteristics of this structure, ambient vibration tests were performed. Four setups were designed to cover all the degrees of freedom of interest involving the floors from the ground to the roof. A recently developed Bayesian method incorporating multi‐setups was employed to identify the modal properties by using the data in all the setups simultaneously. In addition to the most probable values, the associated posterior uncertainties were also obtained, providing an estimation tool to assess the accuracy of the modal parameters. These results were utilized to investigate the modal properties of this structure. The influence due to the earthquake was also studied based on the observation in the field. Before the full‐scale field tests, shaking table tests were also implemented. The dynamic properties from the two different tests, as well as their posterior uncertainties, were compared and discussed in the paper. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-03T02:41:06.979489-05:
      DOI: 10.1002/stc.1816
       
  • Impact energy level assessment of composite structures using
           MUSIC‐ANN approach
    • Authors: Yongteng Zhong; Jiawei Xiang, Haifeng Gao, Yuqing Zhou
      Abstract: Impact damage effects on the residual mechanical properties of the structure can be quite detrimental, and failure patterns depend strongly on the impact energy levels. This paper presents impact energy level assessment method using 2D multiple signal classification (MUSIC) and artificial neural network (ANN) approach for composite structures. Because uniform linear array has the shortcoming of the half‐plane mirror effect, 2D MUSIC algorithm using a plum blossom sensor array is firstly applied to locate the position of impact and extract impact energy feature. Secondly, the relation impact energy feature, impact position, and impact energy level at different measurement points are established using ANN approach. Through the trained ANN, the impact energy level can be predicted when the position and impact energy feature results of unknown impact are given as input. Finally, the proposed method is applied to a quasi‐isotropic epoxy laminate plate and a large stiffened carbon fiber composite structure showing its successful performance on composite structure. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-03T02:26:41.036773-05:
      DOI: 10.1002/stc.1815
       
  • Proof of concept of the structural health monitoring of framed structures
           by a novel combined experimental and theoretical approach
    • Authors: D. Isidori; E. Concettoni, C. Cristalli, L. Soria, S. Lenci
      Abstract: One of the most important issues in engineering is the detection of structural damages. During its life cycle, a building, besides the exposure to operational and environmental forces, can be subjected to earthquakes or to other non‐ordinary loads. These events may have a deep impact on the building safety, and thus, a continuous monitoring of the structure health conditions becomes desirable or even necessary in many cases. In this context, the usage of vibration‐based structural health monitoring (SHM) systems is spreading from big infrastructures applications, like bridges, dams or skyscrapers, to the historical heritage and to public or residential buildings. The aim of this work is to propose a combined experimental and numerical methodology to perform the SHM of structures of the civil engineering lying in seismic hazard zones. A relatively low cost SHM prototype system based on this approach is developed. The data acquired by the system are provided to a finite element method (FEM) numerical model to detect the appearing, the rise and the distribution of local damages and to estimate a global damage level. The system has been tested and calibrated on a three‐storey prototype model. The procedure for the estimation of the damage level is calibrated by comparing the experimental quantities measured during cyclic failure tests with the FEM model predictions. Copyright © 2015 John Wiley & Sons, Ltd.
      PubDate: 2015-11-02T05:55:39.331486-05:
      DOI: 10.1002/stc.1811
       
 
 
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