ORCID Profile
0000-0001-5319-5858
Current Organisations
Huazhong University of Science and Technology
,
The Hong Kong Polytechnic University
,
Hong Kong Polytechnic University
,
Nanyang Technological University
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Publisher: Elsevier BV
Date: 11-2015
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 10-2023
Publisher: American Society of Civil Engineers (ASCE)
Date: 2016
Publisher: World Scientific Pub Co Pte Ltd
Date: 12-2012
DOI: 10.1142/S0219455412500526
Abstract: A huge number of data can be obtained continuously from a number of sensors in long-term structural health monitoring (SHM). Different sets of data measured at different times may lead to inconsistent monitoring results. In addition, structural responses vary with the changing environmental conditions, particularly temperature. The variation in structural responses caused by temperature changes may mask the variation caused by structural damages. Integration and interpretation of various types of data are critical to the effective use of SHM systems for structural condition assessment and damage detection. A data fusion-based damage detection approach under varying temperature conditions is presented. The Bayesian-based damage detection technique, in which both temperature and structural parameters are the variables of the modal properties (frequencies and mode shapes), is developed. Accordingly, the probability density functions of the modal data are derived for damage detection. The damage detection results from each set of modal data and temperature data may be inconsistent because of uncertainties. The Dempster–Shafer (D–S) evidence theory is then employed to integrate the in idual damage detection results from the different data sets at different times to obtain a consistent decision. An experiment on a two-story portal frame is conducted to demonstrate the effectiveness of the proposed method, with consideration on model uncertainty, measurement noise, and temperature effect. The damage detection results obtained by combining the damage basic probability assignments from each set of test data are more accurate than those obtained from each test data separately. Eliminating the temperature effect on the vibration properties can improve the damage detection accuracy. In particular, the proposed technique can detect even the slightest damage that is not detected by common damage detection methods in which the temperature effect is not eliminated.
Publisher: Elsevier BV
Date: 09-2001
Publisher: World Scientific Pub Co Pte Ltd
Date: 03-06-2022
DOI: 10.1142/S0219455422501619
Abstract: Structural damage identification based on the long short-term memory (LSTM) neural network (NN) is proposed in this study. To address the hyperparameters selection problem for the LSTM, the Jaya algorithm is applied to minimize the difference between the observed and predicted data in the validation datasets and determine the LSTM network’s optimal hyperparameters, including the number of nodes, learning rate, and maximum iteration number. Frequency-domain data, such as natural frequencies and mode shapes, are used as input of the network, and then damage locations and extents are utilized as output. Measurement uncertainties are introduced during NN training to improve the robustness of the model. Numerical and experimental studies showed that the proposed method can identify structural damage accurately when measurement noise is considered, even for damage scenarios beyond the training datasets.
Publisher: American Society of Civil Engineers (ASCE)
Date: 05-2008
Publisher: Elsevier BV
Date: 07-2017
Publisher: Hindawi Limited
Date: 05-2020
DOI: 10.1002/STC.2521
Publisher: SAGE Publications
Date: 16-09-2021
DOI: 10.1177/13694332211042780
Abstract: The constant changes to which telecommunications have accustomed us in recent decades oblige a similar adaptation in other branches of engineering. Structures such as monopoles and short lattice towers are becoming increasingly wind-sensitive and dynamically active with the introduction of 5G technology, which will require new larger and heavier antenna equipment. Expert consultants agree the need to revise the current accounting for structural d ing that has not changed in design codes after more than 30 years. A complete set of full-scale field tests is presented to obtain reliable structural d ing values in short communications structures. The described methodology analyses free-decaying responses obtained after excitation of the main analysed cantilevered modes in the time domain. A standardized acquisition system based on local accelerometers and an external innovative system using the Video Gauge TM system are required to obtain the desired responses, which use curve-fitting and the eigensystem realization algorithm to estimate modal properties such as the corresponding modal structural d ing. The results obtained using the presented methodology agree on higher values of structural d ing for both d ing estimators and perfectly converge with consultant feedback, which suggested over-conservative (i.e. low) values of structural d ing as compared to the conventional values used in civil engineering.
Publisher: Elsevier BV
Date: 07-2012
Publisher: SAGE Publications
Date: 10-09-2019
Abstract: Substructuring methods possess many merits in model updating and damage identification of large-scale structures. With substructuring methods, a global structure is ided into a number of independent substructures. Only the substructures are repeatedly analyzed and the re-analysis of the global structure is thereby avoided. This article reviews widely used dynamic substructuring methods for model updating and damage identification of large-scale structures. These methods can be categorized into forward and inverse substructuring approaches. The former is a conventional process that assembles the vibration properties of each substructure to obtain the vibration properties of the global structure. The latter, on the contrary, disassembles the vibration properties of the global structure into those of the substructures. In each category, both frequency and time domain methods have been developed and will be reviewed.
Publisher: SAGE Publications
Date: 19-10-2021
DOI: 10.1177/13694332211042788
Abstract: Connecting the ends of girders with a continuous slab-deck to make a multiple-span simply supported girder bridge provides many benefits, but there is no suitable nonlinear analysis model which considers continuous slab-deck cracking under tension and bending. In this article, the rotational spring model is further refined to replace the restraining effects at both ends of the girder by the simplified mechanical model associated with axial stiffness, bending stiffness, and shear stiffness. Then, it is introduced into the analysis of continuous slab-deck. The more accurate rotations and displacements of both ends of continuous slab-deck are obtained to investigate the more precise moment and tension of the continuous slab-deck. Furthermore, this article presents an improved nonlinear analysis model of continuous slab-deck based on a detailed boundary rotational spring model. The displacements of important positions and the strain of key components in continuous slab-deck after cracking are investigated by numerical analysis and full-scale model test to verify the accuracy of the proposed nonlinear analysis model. The result shows that the nonlinear analysis model presented in this article could successfully evaluate the depth of cracks and the stress of rebars in continuous slab-deck, and it is instructional in predicting the cracking state of the continuous slab-deck and the reinforcement design.
Publisher: American Society of Civil Engineers (ASCE)
Date: 2008
Publisher: Elsevier BV
Date: 06-2020
Publisher: SAGE Publications
Date: 24-06-2019
Abstract: Accurate measurement of dynamic displacement is important for the structural health monitoring and safety assessment of supertall structures. However, the displacement of a supertall structure is difficult to be accurately measured using the conventional methods because they are either inaccurate or inconvenient to be set up in practice. This study provides an accurate and economical method to measure dynamic displacement of supertall structures accurately by fusing acceleration and strain data, which are generally available in the structural health monitoring system. Dynamic displacement is first derived from the measured longitudinal strains based on geometric deformation without requiring mode shapes. An optimization technique is utilized to optimize the deployment of strain sensors for achieving more accurate strain-derived displacement. The strain-derived displacement is then combined with measured acceleration via a multi-rate Kalman filtering approach. Applications to a numerical supertall structure and a laboratory cantilever beam verify that the proposed method accurately estimates displacement including both high-frequency and pseudo-static components, under different noise cases and s ling rates. A full-scale field test on the 600 m-high Canton Tower is implemented to validate the applicability of the proposed method to real supertall structures. Error analysis demonstrates that the data fusion displacement is more accurate than the global position system-measured displacement in the time and frequency domains.
Publisher: Hindawi Limited
Date: 18-02-2022
DOI: 10.1002/STC.2937
Publisher: MDPI AG
Date: 25-03-2018
DOI: 10.3390/IJMS19040981
Publisher: SAGE Publications
Date: 27-01-2023
DOI: 10.1177/13694332231153976
Abstract: This work provides a comprehensive review of previous studies concerning the static thermal behaviors of various types of bridges, including beam bridges, arch bridges, cable-stayed, and suspension bridges. Given that thermal behaviors are closely associated with the temperature distribution of bridges, the basis of the heat transfer analysis is briefly introduced first. The studies of the temperature distribution and the temperature actions of each type of bridge are then reviewed from the perspective of theoretical analysis, numerical simulation, experimental tests, and field monitoring. Finally, some existing problems are discussed, and future research topics are recommended.
Publisher: Elsevier BV
Date: 2014
Publisher: Elsevier BV
Date: 12-2012
Publisher: SAGE Publications
Date: 02-2011
Publisher: Elsevier BV
Date: 02-2014
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 02-2013
Publisher: World Scientific Pub Co Pte Ltd
Date: 12-05-2023
DOI: 10.1142/S0219455424500056
Abstract: This paper develops a modal derivative enhanced Kron’s substructuring method to calculate the structural responses and response sensitivities of geometrically nonlinear systems. The proposed method ides the global structure into substructures, which are then assembled in a dual form. The substructural displacements are approximated around the initial linear equilibrium position by using a quadratic modal manifold governed by a few master modes only. A time-variant reduction basis augmented by the master modal derivatives is derived from the quadratic modal manifold, enabling the geometric nonlinearities to be accurately captured. With the reduction basis, the global system is transformed into a reduced one containing the master modes only. Subsequently, the master modal responses and response sensitivities are solved efficiently from the reduced system. The global structural responses and response sensitivities are finally recovered from the master modal solutions based on the quadratic modal manifold. The effectiveness of the proposed method is demonstrated through its application to a thin plate structure. The reduced system enjoys the merit of Kron’s substructuring method that does not contain the interface degrees of freedom. Besides, the proposed reduced system is formed from the quadratic modal manifold directly. Its size is equal to the number of master modes of the substructures and smaller than that of the conventional method, where its size grows quadratically with the number of master modes.
Publisher: Elsevier BV
Date: 02-2016
Publisher: Elsevier BV
Date: 06-2003
Publisher: Elsevier BV
Date: 12-2011
Publisher: American Society of Civil Engineers (ASCE)
Date: 07-2002
Publisher: Elsevier BV
Date: 05-2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2022
Publisher: Elsevier BV
Date: 03-2019
Publisher: Hindawi Limited
Date: 23-06-2016
DOI: 10.1002/STC.1900
Publisher: Wiley
Date: 2002
DOI: 10.1002/EQE.137
Publisher: Elsevier BV
Date: 2017
Publisher: Medknow
Date: 2018
Publisher: Springer Science and Business Media LLC
Date: 15-07-2010
Publisher: World Scientific Pub Co Pte Lt
Date: 05-01-2014
DOI: 10.1142/S0219455413500612
Abstract: Shear connectors are generally used to link the slab and girder together in slab-on-girder bridge structures. Damage of shear connectors in such structures will result in shear slippage between the slab and girder, which significantly reduces the load-carrying capacity of bridges. A damage detection approach based on transmissibility in frequency domain is proposed in this paper to identify the damage of shear connectors in slab-on-girder bridge structures with or without reference data from the undamaged structure. The transmissibility, which is an inherent system characteristic, indicates the relationship between two sets of response vectors in frequency domain. Measured input force and acceleration responses from hammer tests are analyzed to obtain the frequency response functions at the slab and girder sensor locations by the experimental modal analysis. The transmissibility matrix that relates the slab response to the girder response is then derived. By comparing the transmissibility vectors in undamaged and damaged states, the damage level of shear connectors can be identified. When the measurement data from the undamaged structure are not available, a study with only the measured response data in the damaged state for the condition assessment of shear connectors is also conducted. Numerical and experimental studies on damage detection of shear connectors linking a concrete slab to two steel girders are conducted to validate the accuracy and efficiency of the proposed approach. The results demonstrate that the proposed method can be used to identify shear connector damages accurately and efficiently. The proposed method is also applied to the condition evaluation of shear connectors in a real composite bridge with in-field testing data.
Publisher: SAGE Publications
Date: 18-05-2022
DOI: 10.1177/13694332221102223
Abstract: This paper presents a framework for the conditional simulation of a 3D nonstationary wind field for super-long sea-crossing bridges based on wind speed time histories measured by limited anemometers on site. The variations of wind characteristics along the bridge deck with multi-elements are considered in this framework. The wind characteristics, including mean wind speeds, mean wind directions, turbulence intensities, turbulence integral scales, evolutionary wind spectra and spectral parameters, coherence functions and function parameters, at the measurement points are first obtained by analyzing the measured wind speed time histories. The wind characteristics are then extended over all the simulation points along the deck of the sea-crossing bridge using the spatial interpolation method and considering the variation of deck height above the sea level using the profiles of mean wind speeds, turbulence intensities and turbulence integral scales estimated from the measured wind speed time histories. After working out wind cross correlation functions, wind speed time histories at all simulation points over the sea-crossing bridge can be conditionally simulated. The proposed framework is finally applied to a real 22.9 km sea-crossing bridge under Typhoon Higos. The conditionally simulated wind speed time histories at all simulation points of the bridge are acceptable and consist a complete wind field which can be used for the buffeting analysis of the bridge.
Publisher: Elsevier BV
Date: 09-2000
Publisher: Elsevier BV
Date: 11-2020
Publisher: Elsevier BV
Date: 04-2022
Publisher: Elsevier BV
Date: 05-2014
Publisher: Hindawi Limited
Date: 08-10-2018
DOI: 10.1002/STC.2274
Publisher: Springer Science and Business Media LLC
Date: 09-2007
Publisher: SAGE Publications
Date: 28-03-2017
Abstract: The vibration of beams on foundations under a vehicular load has attracted wide attention for decades. The problem has numerous applications in several fields such as highway structures. However, most of analytical or semi-analytical studies simplify the vehicular load as a concentrated point or distributed line load with the constant or harmonically varying litude, and neglect the presence of the vehicle and the road irregularity. This article carries out an analytical study of vibration on an infinite Pasternak-supported Timoshenko beam under vehicular load which is generated by the passage of a quarter car on a road with harmonic surface irregularity. The governing equations of motion are derived based on Hamilton’s principle and Timoshenko beam theory and then are solved in the frequency–wavenumber domain with a moving coordinate system. The analytical solutions are expressed in a general form of Cauchy’s residue theorem. The results are validated by the case of an Euler–Bernoulli beam on a Winkler foundation, which is a special case of the current system and has an explicit form of solution. Finally, a numerical ex le is employed to investigate the influence of properties of the beam (the radius of gyration and the shear rigidity) and the foundation (the shear viscosity, rocking, and normal stiffness) on the deflected shape, maximum displacement, critical frequency, and critical velocity of the system.
Publisher: Hindawi Limited
Date: 02-2009
DOI: 10.1002/STC.303
Publisher: World Scientific Pub Co Pte Lt
Date: 09-2013
DOI: 10.1142/S1793431113500280
Abstract: In this paper, a mesoscale model is adopted to simulate concrete behavior under dynamic split tension. The concrete material is assumed to comprise coarse aggregates, mortar matrix, and an interfacial transition zone (ITZ). In the mesh generation process, random coarse aggregate particles are generated from a certain aggregate size distribution and then placed into the mortar matrix with ITZ between the coarse aggregate edge and the mortar matrix. Different aggregate shapes, such as circular, oval, and polygons are modeled to analyze the gravel and crushed stone aggregates. Numerical simulation is used to model the dynamic damage responses of a typical cylinder concrete specimen and a cube specimen under split tension. Velocity boundary is added as the dynamic loading. Reasonable tensile stress–strain relationships are obtained at the macroscale level and the detailed stress wave distribution and the crack pattern are obtained at the mesoscale level. These numerical results agree well with conventional experimental results. It also shows that cracks are affected by aggregate distribution.
Publisher: Elsevier BV
Date: 09-2003
Publisher: World Scientific Pub Co Pte Lt
Date: 06-2014
DOI: 10.1142/S0219455414400069
Abstract: Traditional structural system identification and damage detection methods use vibration responses under single excitation. This paper presents an auto/cross-correlation function-based method using acceleration responses under multiple ambient white noise or impact excitations. The auto/cross-correlation functions are ided into two parts. One is associated with the structural parameters and the other with the energy of the excitation. These two parts are updated sequentially using a two-stage method. Numerical and experimental studies are conducted to demonstrate the accuracy and robustness of the proposed method. The effects of measurement noise and number of measurement points on the identification results are also studied.
Publisher: Hindawi Limited
Date: 2013
DOI: 10.1155/2013/706798
Abstract: In substructuring methods, the substructures are independently analyzed under free-free conditions. For a free-free substructure, its stiffness matrix is singular and rank deficient due to rigid body motion. The variables associated with the inverse of the stiffness matrix are not easy to be accurately determined in the usual manner. This study expands on the previous research on the substructuring methods by taking a deeper look at the analysis of a free-free substructure. A well-conditioned stiffness matrix is constructed for the analysis of a free-free structure. Some difficulties associated with the analysis of the free-free substructures can be solved in a simple and effective way. The substructural eigensolutions and eigensensitivity are solved from the well-conditioned stiffness matrix, other than the singular stiffness matrix. The proposed well-conditioned eigenequation is accurate and efficient to calculate the substructural eigensolutions and eigensensitivity. The properties addressed in this paper are not limited to be used for the analysis of a free-free substructure in many substructuring methods, and they are promising to be generalized to a range of analysis relevant to a free-free structure.
Publisher: Wiley
Date: 14-02-2011
Publisher: SAGE Publications
Date: 02-2094
DOI: 10.1260/1369-4332.15.10.1739
Abstract: The integrity of ageing bridges is in doubt because of increasing traffic loads, deterioration of materials, possible damage during service, and revised code requirements. Traditional methods in prediction of load varying capacity of bridges are usually based on the design blueprints and may not reflect the bridge condition as is. In this paper, the nonlinear finite element analysis, incorporating the model updating technique, is used to predict the behaviour of a 30-year-old slab-girder bridge. The original finite element model based on the design drawings is updated by modifying the stiffness parameters of the girders, slab, shear connectors and bearings so that the vibration properties of the model match the field vibration measurement data. The updated model represents the present condition of the bridge better than the original model that is based on the design blueprints. The load carrying capacity of the bridge is then calculated using the original and updated finite element models, respectively, with consideration of nonlinear material properties. The comparison shows that the bridge load carrying capacity under the present condition is lower than that under the design condition, whereas is still above the design requirement. The influence of the shear connectors on the load carrying capacity is specially investigated.
Publisher: Elsevier BV
Date: 2011
Publisher: Elsevier BV
Date: 03-2018
Publisher: Elsevier BV
Date: 05-2017
Publisher: American Society of Civil Engineers
Date: 11-03-2010
Publisher: Elsevier BV
Date: 2013
Publisher: SAGE Publications
Date: 05-2013
DOI: 10.1260/1369-4332.16.5.899
Abstract: Structural damage detection methods using vibration measurements have been developed for decades. Measurement selections may affect damage detection results, because inevitable uncertainties are involved in vibration testing. A new sensor placement index is defined as the ratio of two parameters, namely, the contribution of measurement points to a Fisher information matrix, and the damage sensitivity to the measurement noise. A large value of the contribution vector represents that the corresponding measurement points are sensitive to the damage and measurements at these points are more prominent for structural damage identification, whereas a small noise sensitivity value indicates measurement points that are less influenced by noises. Consequently, the points with large index values are chosen as the measurement subset. The effectiveness of the proposed technique is verified using a laboratory-tested steel frame. The damage detection using different measurement selection schemes shows that the present technique can identify multiple damages of the structure more accurately. The effect of the measurement number is also investigated.
Publisher: SAGE Publications
Date: 02-2011
DOI: 10.1260/1369-4332.14.1.103
Abstract: Massive infrastructure projects developed in Hong Kong make for big challenges and unique opportunities for engineers and researchers. The construction of the cables-stayed Stonecutters Bridge sets up a new landmark in the bridge engineering community, with its main span exceeding 1,000 m as well as its sophisticated instrumentation system comprising more than 1,500 sensors. The development of structural health monitoring (SHM) technology has evolved for over 10 years in Hong Kong since the implementation of the so-called “Wind And Structural Health Monitoring System (WASHMS)” on the suspension Tsing Ma Bridge in 1997. The successful engineering paradigms of implementing and operating SHM systems for five cable-supported bridges and experiences gained by practice and research in the past decade have promoted the applications of this technology beyond Hong Kong and extending from long-span bridges to high-rise structures. In this paper, the evolution in the design methodology for SHM systems, the advancement in several aspects of SHM technology, and a performance comparison between the early implemented and lately developed SHM systems for large-scale bridges are first outlined. Subsequently, the concept of the so-called “life-cycle structural health monitoring (LSHM)” is addressed by exploring the integration of in-construction monitoring and in-service monitoring and by realizing such an integrated system to a super-tall tower structure. The issue on how an SHM system benefits structural vibration control is also discussed.
Publisher: Elsevier BV
Date: 07-2015
Publisher: Elsevier BV
Date: 06-2009
Publisher: Elsevier BV
Date: 07-2011
Publisher: American Society of Civil Engineers (ASCE)
Date: 03-2006
Publisher: Springer Science and Business Media LLC
Date: 04-07-2015
Publisher: Elsevier BV
Date: 06-2021
Publisher: Springer Science and Business Media LLC
Date: 18-08-2013
Publisher: Elsevier BV
Date: 06-2023
Publisher: Trans Tech Publications, Ltd.
Date: 07-2011
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMM.71-78.733
Abstract: In the mesoscale modeling, concrete is assumed consisting of three components, i.e., coarse aggregates, mortar matrix, and the interfacial transition zone (ITZ), each with different material behavior. The shape and the percentage of the coarse aggregate are the key factors in the mesoscale numerical simulation. The present paper investigates the effect of the coarse aggregate shape on the concrete behavior under high strain rate compression. Simplified methods are adopted to construct the aggregate distribution. Three different aggregate shapes, i.e., circular, oval and polygons, are generated to model the gravel and crushed stone aggregates, respectively. Using these different aggregate shapes, concrete specimens under high strain rate compression are modeled. Numerical results show that the aggregate shapes have a significant effect on the crack path, whereas little effect on the overall responses of the concrete specimen.
Publisher: Elsevier BV
Date: 06-2016
Publisher: Elsevier BV
Date: 2011
Publisher: Elsevier BV
Date: 07-2007
Publisher: Hindawi Limited
Date: 15-04-2021
DOI: 10.1002/STC.2738
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2012
Publisher: SAGE Publications
Date: 30-06-2009
Abstract: Although vibration-based structural damage detection methods have demonstrated various degrees of success, the damage detection of civil structures still remains as a challenging task. The main obstacles include the insensitivity to local damage and the high sensitivity to measurement noise. A new structural damage detection method based on the statistical moments of dynamic responses of a structure has been recently proposed by the authors, and the numerical study manifested that the proposed method is sensitive to local structural damage but insensitive to measurement noise. The experimental investigation on this method is presented in this article. Three shear building models with and without damage were built and subjected to ground motions generated by a shaking table. The displacement and acceleration responses of each building model at each floor were recorded. The recorded ground motion and building responses as well as identified structural d ing ratios were then used to identify damage locations and severities using the statistical moment-based damage detection method. The identified damage locations and severities were compared with the theoretical values. The comparison is found satisfactory, and the method proposed is effective and feasible.
Publisher: Hindawi Limited
Date: 25-03-2018
DOI: 10.1002/STC.2175
Publisher: Springer International Publishing
Date: 24-10-2021
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2018
Publisher: Springer Science and Business Media LLC
Date: 24-01-2013
Publisher: Elsevier BV
Date: 08-2019
Publisher: SAGE Publications
Date: 26-03-2017
Abstract: Since the last two decades, the electro-mechanical impedance technique has undergone extensive theoretical and experimental transformations coupled with the evolution of newer practical adaptations and variants. Notable among these are the metal wire–based variant, the dual piezo configuration and the embedded configuration, over and above the conventional surface-bonded configuration. Although there is a plethora of electro-mechanical impedance–related research devoted to metallic structures, only a limited number of studies are available for reinforced concrete structures, which are characterized by more complex behaviour and pose multiple problems for the electro-mechanical impedance sensors such as small range and high d ing due to heterogeneous constitution. This article presents, for the first time, a comprehensive comparative study covering four different variants, namely, the surface-bonded single piezo configuration, the embedded single piezo configuration and the metal wire single piezo configuration in electro-mechanical impedance technique for structural health monitoring of a real-life-sized reinforced concrete beam subjected to destructive testing. The article also proposes a modified and more practical version of the dual piezo configuration called the modified dual piezo configuration, employing concrete vibration sensors. It is found that the modified dual piezo configuration is the most expedient among all variants in capturing the damage with respect to the first occurrence of cracks and the final warning of ultimate failure. Metal wire single piezo configuration is good in detecting the first level of damage however, its efficiency ceases thereafter when crack size increases. It can be considered as an alternative to surface-bonded single piezo configuration in the scenarios where the damage level is incipient. The sensitivity of the modified dual piezo configuration increases with increasing number of actuators connected in parallel due to an increase in the output current. Also, contrary to the surface-bonded single piezo configuration, the susceptance signature of the modified dual piezo configuration is equally sensitive to damage due to the absence of capacitance part in its admittance signature. Hence, its susceptance can also be used for damage severity measurement for incipient damage level in reinforced concrete structures. The surface-bonded single piezo configuration is found to be best in quantifying damage severity in terms of the equivalent stiffness parameter. Embedded single piezo configuration and metal wire single piezo configuration, on the other hand, correlate well with the global dynamic stiffness of the structure. Overall, the proposed integration enables an early detection of damage, its propagation and improved severity measurement for reinforced concrete structures, thus contributing to new application protocols.
Publisher: Wiley
Date: 20-11-2003
DOI: 10.1002/NME.876
Publisher: Elsevier BV
Date: 08-2021
Publisher: SAGE Publications
Date: 02-06-2020
Abstract: Existing studies on sparse Bayesian learning for structural damage detection usually assume that the posterior probability density functions follow standard distributions which facilitate to circumvent the intractable integration problem of the evidence by means of numerical s ling or analytical derivation. Moreover, the uncertainties of each mode are usually quantified as a common parameter to simplify the calculation. These assumptions may not be realistic in practice. This study proposes a sparse Bayesian method for structural damage detection suitable for standard and nonstandard probability distributions. The uncertainty corresponding to each mode is assumed as different. Variational Bayesian inference is developed and the posterior probability density functions of each unknown are in idually derived. The parameters are found to follow the gamma distribution, whereas the distribution of the damage index cannot be directly obtained because of the nonlinear relationship in its posterior probability density function. The delayed rejection adaptive Metropolis algorithm is then adopted to generate numerical s les of the damage index. The coupled damage index and parameters in the variational Bayesian inference are successively calculated via an iterative process. A laboratory-tested frame is utilised to verify the effectiveness of the proposed method. The results indicate that the sparse damage can be accurately detected. The proposed method has the advantage of high accuracy and broad applicability.
Publisher: Elsevier BV
Date: 06-2018
Publisher: Springer Science and Business Media LLC
Date: 12-2011
Publisher: Elsevier BV
Date: 05-2020
Publisher: MDPI AG
Date: 04-07-2019
DOI: 10.3390/EN12132573
Abstract: When compared with horizontal-axis wind turbines, vertical-axis wind turbines (VAWTs) have the primary advantages of insensitivity to wind direction and turbulent wind, simple structural configuration, less fatigue loading, and easy maintenance. In recent years, large-scale VAWTs have attracted considerable attention. Wind loads on a VAWT must be determined prior to structural analyses. However, traditional blade element momentum theory cannot consider the effects of turbulence and other structural components. Moreover, a large VAWT cannot simply be regarded as a planar structure, and 3D computational fluid dynamics (CFD) simulation is computationally prohibitive. In this regard, a practical wind load simulation method for VAWTs based on the strip analysis method and 2D shear stress transport (SST) k-ω model is proposed. A comparison shows that the wind pressure and aerodynamic forces simulated by the 2D SST k-ω model match well with those obtained by 2.5D large eddy simulation (LES). The influences of mean wind speed profile, turbulence, and interaction of all structural components are considered. A large straight-bladed VAWT is taken as a case study. Wind loads obtained in this study will be applied to the fatigue and ultimate strength analyses of the VAWT in the companion paper.
Publisher: Hindawi Limited
Date: 29-09-2017
DOI: 10.1002/STC.2107
Publisher: SAGE Publications
Date: 21-11-2016
Abstract: The electro-mechanical impedance technique has developed rapidly during the past few decades as a reliable health monitoring component of civil structures. However, the high cost of impedance analyzer/LCR meter conventionally used for data acquisition in the electro-mechanical impedance technique restricts its wide use in real applications. This article provides a comprehensive study of exploring the low-cost electro-mechanical impedance technique for health monitoring of concrete under destructive testing using multiple piezo configurations. The experimental scheme ensures separate acquisition of both the real and the imaginary components of the electro-mechanical impedance signature for detailed analysis, a feature not available in some previous low-cost adaptations. The piezo configurations covered here for comparison are the surface-bonded piezo configuration, the embedded piezo configuration, and the metal wire piezo configuration. The repeatability of the proposed low-cost electro-mechanical impedance technique is checked and the results are compared with the traditional counterpart utilizing conventional LCR meter. The two electro-mechanical impedance approaches show similar trends of the conductance signature for all configurations. In particular, the metal wire piezo configuration can be adopted as an excellent alternative in practice for reinforced concrete structures when the direct surface bonding is not feasible. Overall, the low-cost version of the electro-mechanical impedance technique is effective to detect the presence of the damage.
Publisher: Elsevier BV
Date: 05-2011
Publisher: Elsevier BV
Date: 02-2014
Publisher: Hindawi Limited
Date: 25-08-2020
DOI: 10.1002/STC.2629
Publisher: Hindawi Limited
Date: 17-01-2012
DOI: 10.1002/STC.515
Publisher: Hindawi Limited
Date: 18-02-2019
DOI: 10.1002/STC.2343
Publisher: SAGE Publications
Date: 2013
DOI: 10.1260/1369-4332.16.1.219
Abstract: Instability damage may occur in some members of the transmission tower subjected to the downburst, and eventually the damage accumulation may further lead to the failure of the tower. Therefore, it is extremely essential to identify and repair the damaged major vertical members in tower body timely. The relationship surface of instable member among axial compression force, bending moment at the end and axial stiffness is determined. The results show that the axial stiffness of the instability members reduces to zero gradually. Accordingly, a two-step detection method of the major vertical member instability damage is presented. The first step detection is used to find the possible buckling damaged regions by using wavelet packet energy curvature change rate index. The second step is used to identify location of buckling damaged major member that appears in the possible damaged subregions based on the theory of modal strain energy and interval estimation. Finally, the proposed method is applied to a realistic transmission tower and experimental verified with a steel tube tower. The results indicate that the two-step detection method is effective and feasible.
Publisher: Hindawi Limited
Date: 22-07-2023
DOI: 10.1155/2023/2430011
Abstract: Structural health monitoring (SHM) systems may suffer from multiple patterns of data anomalies. Anomaly detection is an essential preprocessing step prior to the use of monitoring data for structural condition assessment or other decision making. Deep learning techniques have been extensively used for automatic category classification by training the network with labelled data. However, because the SHM data are usually large in quantity, manually labelling these abnormal data is time consuming and labour intensive. This study develops a semisupervised learning-based data anomaly detection method using a small set of labelled data and massive unlabelled data. The MixMatch technique, which could mix labelled and unlabelled data using MixUp, is adopted to enhance the generalisation and robustness of the model. A unified loss function is defined to combine information from labelled and unlabelled data by incorporating consistency regularisation, entropy minimisation, and regular model regularisation items. In addition, customised data augmentation strategies for time series are investigated to further improve the model performance. The proposed method is applied to the SHM data from a real bridge for anomaly detection. Results demonstrate the superior performance of the developed method with very limited labelled data, greatly reducing the time and cost of labelling efforts compared with the traditional supervised learning methods.
Publisher: SPIE
Date: 25-11-2008
DOI: 10.1117/12.839257
Publisher: Springer Science and Business Media LLC
Date: 08-01-2012
Publisher: World Scientific Pub Co Pte Lt
Date: 08-2018
DOI: 10.1142/S0219455418400047
Abstract: An accurate finite element (FE) model is frequently used in damage detection, optimization design, reliability analysis, nonlinear analysis, and so forth. The FE model updating of large-scale structures is usually time-consuming or even impossible. This paper proposes a dynamic condensation approach for model updating of large-scale structures. The eigensolutions are calculated from a condensed eigenequation and the eigensensitivities are calculated without selection of additional master DOFs, which is helpful to improve the efficiency of FE model updating. The proposed model updating method is applied to an eight-storey frame and the Jun Shan Yangtze Bridge. By employing the dynamic condensation approach, the number of iterations for the eigensensitivities is gradually increased according to the model updating process, which contributes to accelerate the convergence of model updating.
Publisher: SAGE Publications
Date: 04-06-2021
DOI: 10.1177/14759217211021938
Abstract: The l 1 regularization technique has been developed for damage detection by utilizing the sparsity feature of structural damage. However, the sensitivity matrix in the damage identification exhibits a strong correlation structure, which does not suffice the independency criteria of the l 1 regularization technique. This study employs the elastic net method to solve the problem by combining the l 1 and l 2 regularization techniques. Moreover, the proposed method enables the grouped structural damage being identified simultaneously, whereas the l 1 regularization cannot. A numerical cantilever beam and an experimental three-story frame are utilized to demonstrate the effectiveness of the proposed method. The results showed that the proposed method is able to accurately locate and quantify the single and multiple damages, even when the number of measurement data is much less than the number of elements. In particular, the present elastic net technique can detect the grouped damaged elements accurately, whilst the l 1 regularization method cannot.
Publisher: Elsevier BV
Date: 05-2021
Publisher: SAGE Publications
Date: 19-05-2019
Abstract: The guided wave technique is commonly used in the health monitoring of thin-walled structures because the guided waves can propagate far in the structures without much energy loss. However, understanding of the wave propagation in bounded layered structures is still lacking. In this study, the Lamb wave field of single- and multi-layer plates excited by surface-mounted piezoelectric wafer active sensors is theoretically analyzed using the normal mode expansion method, which is based on the elastodynamic reciprocity relation and utilizes the orthogonality relations of the Lamb wave modes. The mode participation factors of Lamb wave in single- and multi-layer isotropic plates are derived. The time domain responses are obtained through the inverse Fourier transform of the structural response spectrum, which is obtained by multiplying the transfer function with the excitation frequency spectrum. The developed normal mode expansion method is first applied to an aluminum single-layer plate. The obtained analytical tuning curves and out-of-plane velocity of the plate are in good agreement with the numerical and experimental results. Finally, the analytical wave responses of an aluminum–adhesive–steel triple-layer plate are verified through comparison with the finite element analysis and experiment. The proposed normal mode expansion method provides a reliable and accurate calculation of the wave field in single- and multi-layer plates.
Publisher: Elsevier BV
Date: 12-2011
Publisher: MDPI AG
Date: 04-07-2019
DOI: 10.3390/EN12132584
Abstract: Vertical axis wind turbines (VAWTs) exhibit many advantages and great application prospect as compared with horizontal ones. However, large-scale VAWTs are rarely reported, and the codes and guidelines for designing large-scale VAWTs are lacking. Designing a large-scale composite blade requires precise finite element (FE) modeling and stress analysis at the lamina level, while precise modeling of an entire VAWT is computationally intensive. This study proposes a comprehensive fatigue and ultimate strength analysis framework for VAWTs. The framework includes load determination, finite element (FE) model establishment, and fatigue and ultimate strength analyses. Wind load determination has been presented in the companion paper. In this study, laminated shell elements are used to model blades, which are separately analyzed by ignoring the influence of the tower and arms. Meanwhile, beam elements are used to model an entire VAWT to conduct a structural analysis of other structural components. A straight-bladed VAWT in Yang Jiang, China, is used as a case study. The critical locations of fatigue and ultimate strength failure of the blade, shaft, arms, and tower are obtained.
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 02-2014
Publisher: Hindawi Limited
Date: 13-07-2022
DOI: 10.1002/STC.3047
Publisher: Trans Tech Publications, Ltd.
Date: 05-2011
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.243-249.6127
Abstract: Concrete might be subjected to impact or blast loading. To analyze the concrete behaviors under such loading cases, it is of interest to study the dynamic damage and failure behavior of concrete under high strain rate. In the present paper, a mesoscale model is developed to numerically analyze the dynamic damage process of concrete s les under high strain rate tension. In the mesoscale model, the concrete is regarded as a three-phase composite consisting of coarse aggregate, mortar matrix, and interfacial transition zone (ITZ) between the aggregate and the mortar matrix. Different coarse aggregate shapes, such as circular, oval, and polygon, are calculated and compared. It is found that the shapes of the coarse aggregates do affect the tensile strength and failure pattern.
Publisher: SAGE Publications
Date: 07-10-2022
DOI: 10.1177/13694332221130797
Abstract: Varying temperature may cause a non-uniform temperature distribution of a bridge and lead to excessive movement and stresses of the structure. Traditional thermal analyses of bridges adopt a ide-and-conquer approach, which conducts a simplified 2D or local 3D heat-transfer analysis and then a global 3D structural analysis by inputting the calculated temperature into another bridge model. This process requires considerable manual intervention and is inefficient and may lead to inaccurate results. This study develops a unified approach of heat-transfer and structural analyses for the first time to calculate the temperature distribution and the associated responses of an entire structure by integrating the field monitoring data. The arch footbridge at the Hong Kong Polytechnic University is used as a testbed, and a detailed finite element model (FEM) of the bridge is established. The measured air temperature and solar radiation are used as the thermal boundary conditions. The hemisphere technique is adopted to calculate the view factor between different surfaces of the bridge, which are then used to obtain the solar radiation on all external surfaces in different instants on different dates. The 3D global hear-transfer analysis is conducted to obtain the temperature distribution of the entire bridge. The calculated temperature data of the bridge are then automatically input into the same FEM of the bridge to calculate the temperature-induced bridge responses via the structural analysis. The heat-transfer analysis and structural analysis share the same FEM while using different element types. Therefore, the manual intervention is avoided. The calculated and monitored temperature data and responses show a good agreement. The developed new unified approach enables an automatic and efficient analysis of thermal behaviors of bridges. This approach can be extended to other types of bridges.
Publisher: SAGE Publications
Date: 06-2011
DOI: 10.1260/1369-4332.14.3.589
Abstract: Nonlinear vibration of cables in cable-stayed bridges is usually studied by either a ide-and-conquer approach in which interaction between local motion of the cables and global motion of the bridge is not considered, or a coupled cable-beam system which can only represent a simple structure with few degrees of freedom. A cable finite element is presented in this paper which can account for in-plane and out-of-plane motions of the cable. A cable-beam system with frequency ratio of 1:1:2 is employed to verify feasibility of the cable element in analysing nonlinear vibration of the stay cable. Vibrations of the coupled cable-beam system under harmonic and random loadings are calculated and compared with the available analytical solutions that have been verified experimentally. The results demonstrate that the cable finite element can capture nonlinear vibration, in particular auto-parametric vibration of stay cables under both loading cases. Consequently it can be applied to practical structures with multiple cables.
Publisher: Springer Science and Business Media LLC
Date: 03-2010
No related grants have been discovered for Yong Xia.