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This study proposes a frequency domain vehicle-track coupling model for the CRTS (China railways track system)-III type damping track system based on the two-dimensional vehicle-track-viaduct coupling model, and utilizes dynamic compliance method to determine the dynamic compliance for the vehicle and track systems. The accelerations for the viaduct are hereinafter obtained and are compared between CRTS-III damping track system and conventional CRTS-III track system, and the structure-borne noises for near field and far field of the viaduct are assessed with finite element method (FEM). The acoustic contribution rates for the substructures of the viaduct to the near-field and far-field noises are analyzed. The results reveal that in comparison with the conventional CRTS-III system, the CRTS-III damping track system can mitigate the viaduct acceleration peak with 69.9%, and mitigate the average acceleration with 60.4%. The near field and far field noise measurement points are captured for the CRTS-III damping track system, the sound pressure levels decline by 8.15 dB and 8.36 dB, respectively. The acoustic contribution rates for the viaduct top plate reach 65.28% and 68.30%, respectively. The viaduct top plate thus becomes the major noise source and the damping track system can effectively mitigate the structure-borne noise of the viaduct.

Marine un-bonded flexible pipes wrapped with fiber-reinforced polymer are essential in offshore oil and gas exploration because of their high flexibility and reliability. These flexible pipes may be subjected to tensile loads, compressive loads, and torsional loads, causing the armor wires to undergo large displacements that may result in failure. This study develops a nonlinear simplified finite element model to investigate the mechanical behavior of flexible pipe armor wires under various types of load. The stiffness change rule of flexible pipe armor wires is obtained from numerical simulations of the flexible pipe tensile armor layer under combined loads. The results reveal that the flexible pipe stiffness under combined loads varies significantly from that under single loads, and the combination of different load types can either increase or decrease the stiffness. This study provides essential reference data for the further design, fabrication, and application of flexible pipes.

This study introduces the dynamic impact factor (IF) assessment of a concrete filled steel tube (CFST) butterfly arch bridge with both experimental and numerical results. The modal parameters are identified from the measured accelerations and the IFs are computed from the dynamic strain responses. Four well-known bridge design codes are applied to assess the experimental IFs. A vehicle-bridge coupled vibration system is established to numerically investigate certain effects of vehicle speed, road roughness and structural damping on the IF. Both experimental and numerical results indicate that the IFs of distinct structural components vary significantly, suggesting that a uniform formula is insufficient to describe the impact effect of the whole bridge, which has been generally adopted in many bridge design codes. For the irregular shaped CFST arch bridge, the experimental method is currently the most accurate way to determine dynamic IF. New methodologies must be developed to support the engineers to design safer complex bridges and new formulations must be developed to be part of the bridge codes.

Footbridges usually suffer from vibrations induced by the actions of pedestrians, which calls for various control measures to improve the serviceability. This study described the dynamic analysis and Tuned Mass Damper (TMD) implementation for a single-pylon cable-stayed footbridge scaled model, aimed at providing an experimental case study regarding of vibration control design of slender structures. A scaled model for the real footbridge was designed based on similarity principles. Then, the dynamic behavior of the footbridge was assessed by ambient vibration tests. The natural frequencies and mode shapes were identified from operational vibration measurements by covariance-driven stochastic subspace identification algorithm. The frequency of first vertical bending modes is 2.10 Hz, falling into the human walking frequency range [1.6, 2.4] Hz. Therefore, the footbridge needs vibration control to improve its serviceability. Finally, a self-made TMD using lead, spring and oil buffer was implemented on the scaled model of the footbridge. The laboratory forced vibration test was employed to illustrate the effectiveness of the TMD. By installing TMD, the acceleration response at mid-span of the footbridge was remarkably reduced. The study could provide meaningful reference for vibration control design of the full-scale footbridge.

Structure-borne noise from railway bridges has become increasingly severe due to increased train speeds and axle loads. Constrained layer damping can suppress structural vibration and noise considerably across a wide frequency range by dissipating vibrational energy via damping layer shear deformation. This paper proposes a theoretical method of calculating the train-induced vibration and noise of a constrained layer damping-enhanced railway bridge based on the train–track–bridge coupled vibration, the modal strain energy method, and statistical energy analysis. First, the vibration responses of bridge decks were obtained via train–track–bridge coupled vibration calculations. Second, the constrained layer damping subsystem modal loss factors were determined via modal strain energy analysis and converted to damping loss factors in 1/3 octave band. Third, upon substituting the vibration energies of the decks and the damping loss factors of constrained layer damping subsystems into the statistical energy analysis power balance equations, the transmitted vibration energy results from various bridge subsystems were determined by solving the referenced equations. The structure-borne noise from the bridge was finally determined by analyzing the vibratory energies of all of the bridge subsystems using vibro-acoustic theory. Numerical analysis and field measurements of vibration and noise from a three-span steel–concrete composite bridge before and after constrained layer damping installation were performed. The predicted train-induced vibration and noise agreed well with the measured results. The stringer web and flange vibration velocity levels were reduced by 10.5 dB and 6.1 dB, respectively, and the sound pressure level at a measurement point 25 m (horizontal) from the track centerline and 1.5 m off the ground decreased by 4.3 dB(A).

Large-scale structural optimization often requires numerous finite element analyses to assess the feasibility of the derived solutions during the optimization process, which consume most of the computational cost. To enhance the computational efficiency, this study introduces a filter strategy aiming to eliminate the redundant constraint violation evaluations in large-scale structural optimization using metaheuristic algorithms. Based on the solution selection rule, this study separates the metaheuristic algorithms into two categories: replacement and elitism. The filter mechanism founds on elitism of the metaheuristic algorithms and reduces substantially the number of structural analyses without compromising the effectiveness of the optimization algorithms and the constraint handling techniques. This study also defines a parameter, R, to assess the enhancement performance of the computational efficiency improved by the proposed method. Results from both mathematical simulations and two large-scale structural optimization examples using various metaheuristic algorithms demonstrate that the harmony search (HS) leads always to the lowest R value. The R value is less than 0.4 and is even as small as 0.09 for the 942-bar example, which means over 90% of time savings compared with the penalty method and the Deb rule and the quality of the final optimum also does not depend on the value of R.

Structural damage detection using vibration-based techniques and transmissibility is investigated and proposed with elaborating the mathematical interrelationship between modal assurance criterion (MAC) and cosine similarity measure. From this interrelationship, two new damage indicators, namely cosine based indicator (CI) and extended transmissibility damage indicator (ETDI), are drawn out. Even MAC and cosine similarity measure are normally adopted separately; their kernel agrees well with each other. In this study, we extend these two indicators, derive two new damage indicators, CI and ETDC, and apply them in a transmissibility based structural damage detection technique. In order to verify the feasibility of the developed damage indicators, experimental data for a three-story benchmark structure is adopted. The results from the benchmark demonstrate well performance of both indicators in damage detection, which might imply their potential applicability in further real engineering structures.

Measurement technology based on structured light is a current research focus in the field of visual measurement and is widely applicable to various fields of industrial measurement. How to quickly and accurately locate and continuously track the rail head and rail waist region from dynamically changing laser fringe images remains a key issue to be solved in rail profile detection and analysis. An algorithm based on deep learning is proposed in this paper to realize the recognition of different types of rail profiles. A template-matching driven temporal and spatial contextual tracking algorithm is then employed to achieve rapid tracking of the railhead laser stripe. This method effectively solves the problem of profile measurement for passing trains at crossings and realizes accurate positioning and fast tracking of various types of laser stripes.

Maintenance and repairing in actual engineering for long-term used structures, such as pipelines and bridges, make structural damage detection indispensable, as an unanticipated damage may give rise to a disaster, leading to huge economic loss. A new approach for detecting structural damage using transmissibility together with hierarchical clustering and similarity analysis is proposed in this study. Transmissibility is derived from the structural dynamic responses characterizing the structural state. First, for damage detection analysis, hierarchical clustering analysis is adopted to discriminate the damaged scenarios from an unsupervised perspective, taking transmissibility as feature for discriminating damaged patterns from undamaged ones. This is unlike directly predicting the structural damage from the indicators manifestation, as sometimes this can be vague due to the small difference between damaged scenarios and the intact baseline. For comparison reasons, cosine similarity measure and distance measure are also adopted to draw out sensitive indicators, and correspondingly, these indicators will manifest in recognizing damaged patterns from the intact baseline. Finally, for verification purposes, simulated results on a 10-floor structure and experimental tests on a free-free beam are undertaken to check the suitability of the raised approach. The results of both studies are indicative of a good performance in detecting damage that might suggest potential application in actual engineering real life.

Accurate and efficient damage detection in long-term health monitoring for structures still encounters many difficulties due to the effect of environment. Furthermore, recorded big data requires efficient damage detection algorithm. In this study, an efficient and effective damage detection algorithm is proposed using transmissibility along with Mahalanobis distance and Hotelling T-square. A numerically simulated beam and an experimentally tested laboratory structure are used to validate the proposed algorithm. Results demonstrate good performance of the proposed technique in damage detection.

Detecting structural damage in operational conditions still encounters some difficulties, especially in early-stage, as environmental varieties impose challenges in real engineering applications and may require large computational efforts in the structural health monitoring and potential maintenance. Unlike conventional strategies employing frequency response function or response data, a damage detection methodology is addressed in this study by employing transmissibility functions that retains a strong interrelation with structural damage or deterioration, in order to avoid the measurement of excitation, together with principal component analysis that leads to reduction in computational costs. In this procedure, transmissibility is extracted from the structural responses and main features are selected by principal component analysis for less computational costs. Then, via distance measures damage indicators are constructed for both intact and damaged states, and finally a numerical simulation with a clam...

Bayesian operational modal analysis and modal strain energy are employed for determining the damage and looseness of bolted joints in beam structures under ambient excitation. With this ambient modal identification technique, mode shapes of a damaged beam structure with loosened bolted connections are obtained based on Bayesian theory. Then, the corresponding modal strain energy can be calculated based on the mode shapes. The modal strain energy of the structure with loosened bolted connections is compared with the theoretical one without bolted joints to define a damage index. This approach uses vibration-based nondestructive testing of locations and looseness of bolted joints in beam structures with different boundary conditions by first obtaining modal parameters from ambient vibration data. The damage index is then used to identify locations and looseness of bolted joints in beam structures with single or multiple bolted joints. Furthermore, the comparison between damage indexes due to different looseness levels of bolted connections demonstrates a qualitatively proportional relationship.

This study proposed a novel vibration mitigation slab track plate design to mitigate the vibration induced in urban rail transit operations. The optimal recipe for the newly designed slab track plate is obtained by a series of laboratory tests, and both newly designed vibration mitigation slab track plates and normal slab track plates are fabricated and hereinafter tested. The newly designed slab track plate was examined with a series of laboratory tests in comparison with the normal slab track plate. The PolyMAX method is then adopted for extracting the modal properties, including resonant frequencies, and damping ratios are also determined for both the designed slab and normal slab track plates. A vibration mitigation level (Ls) is defined to address the vibration mitigation performance taking the acceleration response of the normal slab track plate as reference. The newly designed slab track plate demonstrated better dynamic and damping characteristics in comparison with the normal slab track plate. Under the same excitation force, the newly designed slab track plate can mitigate 8.9 dB on average in the frequency range [20, 400] Hz, expressing the feasibility of effective vibration mitigation capacity.

Summary In this paper, a damage-detection approach using the Mahalanobis distance with structural forced dynamic response data, in the form of transmissibility, is proposed. Transmissibility, as a damage-sensitive feature, varies in accordance with the damage level. Besides, Mahalanobis distance can distinguish the damaged structural state condition from the undamaged one by condensing the baseline data. For comparison reasons, the Mahalanobis distance results using transmissibility are compared with those using frequency response functions. The experiment results reveal quite a significant capacity for damage detection, and the comparison between the use of transmissibility and frequency response functions shows that, in both cases, the different damage scenarios could be well detected. Copyright © 2015 John Wiley & Sons, Ltd.

In this paper, a transmissibility based damage detection methodology using artificial intelligence is proposed. Structural health monitoring requires accurate damage detection in real engineering while the environmental uncertain-ties make this a challenge. In order to reduce this effect, artificial intelligence, such as artificial neural networks might be a possible strategy for achieving a better interpretation of the monitored data during operational condition. In this study, transmissibility is taken into account as damage sensitive feature because it accounts for the response data only. Then, auto-associative neural network is employed for detecting the structural damage and predicting its severity. In order to validate our proposed technique, a ten-floor structure is simulated and studied. The results show good perfor-mance in detecting damages. DOI: http://dx.doi.org/10.5755/j01.mech.23.5.15339

This paper presents a methodology for damage detection and localization in composite beams using vibration data, Particle Swarm Optimization (PSO) and Genetic Algorithm (GA). The data was acquired by developing a software that performs dynamic analysis of composite beams based on the Finite Element Method (FEM). The objective function makes use of natural frequencies and Modal Assurance Criterion. After validating the effectiveness of the proposed method, a comparative study between the performances of PSO and GA in detecting multiple and single damage scenarios is carried out. Then, the effect of noise is investigated by taking different noise levels in the modal data. It appears that the noise has a negligible effect on the performance of the presented approaches.DOI: http://dx.doi.org/10.5755/j01.mech.23.4.15254

This paper proposes a methodology to process and interpret the complex signals acquired from the health monitoring of civil structures via scale-space empirical wavelet transform (EWT). The FREEVIB method, a widely used instantaneous modal parameters identification method, determines the structural characteristics from the individual components separated by EWT first. The scale-space EWT turns the detecting of the frequency boundaries into the scale-space representation of the Fourier spectrum. As well, to find meaningful modes becomes a clustering problem on the length of minima scale-space curves. The Otsu&rsquo, s algorithm is employed to determine the threshold for the clustering analysis. To retain the time-varying features, the EWT-extracted mono-components are analyzed by the FREEVIB method to obtain the instantaneous modal parameters and the linearity characteristics of the structures. Both simulated and real SHM signals from civil structures are used to validate the effectiveness of the present method. The results demonstrate that the proposed methodology is capable of separating the signal components, even those closely spaced ones in frequency domain, with high accuracy, and extracting the structural features reliably.

A new transmissibility-based damage detection and quantification approach is proposed. Based on the operational modal analysis, the transmissibility is extracted from system responses and transmissibility coherence is defined and analyzed. Afterwards, a sensitive-damage indicator is defined in order to detect and identify the severity of damage and compared with an indicator developed by other authors. The proposed approach is validated on data from a physics-based numerical model as well as experimental data from a three-story aluminum frame structure. For both numerical simulation and experiment the results of the new indicator reveal a better performance than coherence measure proposed in Rizos et al., 2008, Rizos et al., 2002, Fassois and Sakellariou, 2007, especially when nonlinearity occurs, which might be further used in real engineering. The main contribution of this study is the construction of the relation between transmissibility coherence and frequency response function coherence and the construction of an effective indicator based on the transmissibility modal assurance criteria for damage (especially for minor nonlinearity) detection as well as quantification.

Output-based structural damage detection is becoming increasingly appealing due to its potential in real engineering applications without any restriction regarding excitation measurements. A new transmissibility-based damage detection approach is presented in this study by combining transmissibility with correlation analysis in order to strengthen its performance in discriminating damaged from undamaged scenarios. From this perspective, damage detection strategies are hereafter established by constructing damage-sensitive indicators from a derived transmissibility. A cantilever beam is numerically analyzed to verify the feasibility of the proposed damage detection procedure, and an ASCE (American Society of Civil Engineers) benchmark is henceforth used in the validation for its application in engineering structures. The results of both studies reveal a good performance of the proposed methodology in identifying damaged states from intact states. The comparison between the proposed indicator and the existing indicator also affirms its applicability in damage detection, which might be adopted in further structural health monitoring systems as a discrimination criterion. This study contributed an alternative criterion for transmissibility-based damage detection in addition to the conventional ones.

The delamination problem is very important failure mechanism in certain types of composite structures. Detecting this type of damage using vibration data is currently a problem of interest to the structural health monitoring community. In this paper, we used finite element method with embedded interface for analysing damaged laminated composite structures. The flexibly modal method, in which analysis data is related to finite element modelling, is used to detect and localize delamination. Several numerical examples are presented in order to evaluate the accuracy this approach.

In this research paper, the damage in Carbon Fibre Reinforced Polymer (CFRP) laminate beams under free vibration and simply supported conditions, is investigated numerically by Finite Element Method (FEM) using Matlab program. The developed Cornwell Indicator is used for damage detection and quantification in the considered composite beams. The data was acquired by developing a software that performs dynamic analysis of composite beams based on FEM. The results show that the efficiency of the developed indicator.

Although extensive investigations exist for structural damage detection, which often solely considers the stiffness reduction, or specific damage type like concrete spalling, this study aims to address a general novelty detection procedure for detecting the novelty, or so-called outlier from structural dynamic analysis with applying cosine based indicator in frequency response functions. This study also addresses a short review for the cosine indicator and modal assurance criterion, and their interrelation as well. The eight degree-of-freedom system is considered for the verification, and proves well performance in novelty detection.

System identification performs as a core issue in structural dynamic analysis. In this study, transmissibility coherence is introduced for system identification with recalling the existing techniques based on transmissibility. Unlike previous approaches that require four-point measurement, the proposed methodology in this study only requires two-point measurement. The merit behind this approach is that the transmissibility coherence can be employed to estimate the subtraction of transmissibility between two reference points, by using auto- and cross-spectrum analysis. Verification using experimental data proves the feasibility of the proposed technique.

Beam-like structures are the most common components in real engineering, while single side damage is often encountered. In this study, a numerical analysis of single side damage in a free-free beam is analysed with three different finite element models; namely solid, shell and beam models for demonstrating their performance in simulating real structures. Similar to experiment, damage is introduced into one side of the beam, and natural frequencies are extracted from the simulations and compared with experimental and analytical results. Mode shapes are also analysed with modal assurance criterion. The results from simulations reveal a good performance of the three models in extracting natural frequencies, and solid model performs better than shell while shell model performs better than beam model under intact state. For damaged states, the natural frequencies captured from solid model show more sensitivity to damage severity than shell model and shell model performs similar to the beam model in distinguishing damage. The main contribution of this paper is to perform a comparison between three finite element models and experimental data as well as analytical solutions. The finite element results show a relatively well performance.

Structural Health Monitoring (SHM) and impact monitoring of composite structures have become important research topics in the recent year. In this research, a non-destructive vibration-based damage detection method is formulated using Genetic Algorithm (GA) and compared with classical method. The robustness and reliability of the capability to locate and to estimate the severity of damage, based on changes in dynamic characteristics of a structure, is investigated. The objective function for the damage identification problem is established by using the residual force method (FRM). Numerical experiments using finite element analysis are performed on composite beams with different damage scenarios in order to clarify the validity of the developed technique. The comparison between estimated and real damage illustrates the efficiency of the algorithm in damage detection. The results show that the present approach is correct and efficient for detecting structural local damages in composite beam structures.