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Toxoplasmosis is caused by the protozoon Toxoplasma gondii that can infect almost all warm-blooded hosts including horses and humans. Horse meat is one of the most important meat products for human consumption. However, data on seroprevalence of T. gondii in horses intended for human consumption in Northern China is scarce. Thus, a total of 614 serum samples were collected from Jilin Province and Inner Mongolia Autonomous Region (IMAR) between 2015 and 2017, and were detected the seroprevalence for T. gondii by indirect hemagglutination assay test. In the prevalence study, the overall seroprevalence of T. gondii in horses was 17.92% (110/614) by IHA test, at the cut- off 1:64. Horses collected from Changchun (13.58%, P  = 0.02) has a significantly lower seroprevalence than those from Meihekou City (21.72%) and Tongliao City (22.81%). Moreover, a significant difference of T. gondii seroprevalence was found between horses ages at less than 12 months (22.75%) and ≥12 months or higher (16.42%, P  = 0.002). To our knowledge, this is the first report of seroprevalence of T. gondii in horses in Jilin and IMAR, Northern China. Logistic regression suggested that age and geographical location of horses were identified as risk factors. These findings will provide the useful data for controlling and preventing toxoplasmosis in horses and/or other hosts in China. [ABSTRACT FROM AUTHOR]

Natural frequencies are attractive in structural damage detection as they can be conveniently measured and are usually less contaminated by experimental noise. However, generally natural frequencies alone are not sufficient for a unique solution when applied in finite element model (FEM) updating based damage detection. In view of this, a damage detection method by using a parked vehicle induced frequencies variation is proposed in this paper. Firstly the phenomenon of frequency variation caused by a parked vehicle is illustrated via a simulated simply supported beam. Then a FEM updating based damage detection method is proposed by using measured frequencies of the vehicle-bridge system with the vehicle parked at different locations. Numerical and experimental examples with different damage scenarios are conducted to verify the feasibility of the proposed method. The results indicated that it possesses the ability of taking advantage of the high accuracy and overcomes the insufficient quantity of the natural frequencies for damage detection. [ABSTRACT FROM AUTHOR]

Bored root piles are a new type of pile in which the load-bearing capacity can be significantly improved by jacking prefabricated roots into the soil through reserved holes. In this study, numerical simulations and computations are incorporated with field tests to fully investigate the complex load-bearing behaviour of bored root piles under vertical loading. The established numerical model is validated using a measured load-displacement curve obtained from self-balanced field tests. Using the validated numerical model, the load-transfer mechanism is investigated in terms of the load-displacement curve, axial force, shaft friction, and load-share ratios of different components. Results show that the roots share a significant proportion of the load, whereas the load-share ratios of the different root layers indicate temporal and sequence effects. Parametric studies are performed to investigate the effects of different root configurations on the vertical load-bearing behaviour of bored root piles. The results show that root layer spacing is the most important factor affecting the load-bearing capacity. Three failure modes of bored root piles are formulated in terms of root layer spacing. The results of this study can facilitate the design and application of bored root piles. [ABSTRACT FROM AUTHOR]

Applying signal processing tools on quasi-static moving load induced response to localize damage is extremely promising in the field of structural health monitoring. However, it is still an issue to quantify damage for such methods for the lack of definite correspondence between damage severities and damage indexes they adopted. This paper aims to develop a two-stage method with the ability to quantify structural damages by using the quasi-static moving load induced displacement response. As the displacement response of beam structure caused by quasi-static moving load is in close proximity to displacement influence line (DIL), this paper investigates the correspondence between damage parameters and several DIL related features systematically. Then a damage localization index is defined based on area of the region encircled by the DIL change (DILC) and element (ADE), and a damage quantification equation is established based on the area of the region encircled by the DILC and beam (ADB), respectively. Such a two-stage method can take better advantage of the rich test data provided by moving load test, localize and quantify damage with few sensors rapidly. Numerical and experimental examples are carried out to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Root piles constitute a new type of pile in which a series of prefabricated reinforced concrete roots are inserted into the surrounding soil to improve the bearing capacity of the pile foundation. To investigate the nonlinear behaviour of root piles under lateral loading, an extended beam on nonlinear Winkler foundation (BNWF) model incorporating the soil–root interactions is proposed in this paper. The proposed model is aimed at simultaneously describing the additional bearing capacity provided by roots and the nonlinear soil–root interactions for laterally loaded root piles. Lateral loading tests are conducted on two full–scale root piles to verify the applicability and reliability of the proposed model. It is demonstrated that the proposed model can describe the lateral behaviour of root piles with a reasonable calculation accuracy. Further parametric analyses are conducted to investigate the lateral bearing behaviour of the root piles. It is found that the root pile increases the lateral bearing capacity of the piles owing to the roots. Increasing the number or length of roots and locating them in shallow soil layers can improve the lateral bearing capacity of the root piles. The obtained results are useful for the design and application of root piles. [ABSTRACT FROM AUTHOR]

The transmissibility based operational modal analysis (TOMA) has drawn great attention due to its insensitivity to the nature of external excitation. Different from conventional modal identification approaches working in the frequency domain, it opens up a new path to find the system poles by utilizing mode shape information. Recently, the power spectral density transmissibility (PSDT) driven peak picking (PP) approach was proposed by authors for large-scale linear engineering structures under a single operational loading condition. As a nonparametric method, however, the PSDT-driven PP approach identifies natural frequencies by just observing signal-based features subjectively without fitting a parametric model. An enhanced PSDT approach is proposed in this study. The system poles are identified by employing the least-squares complex frequency-domain (LSCF) estimator, following which the mode shapes are evaluated by utilizing singular value decomposition (SVD) technique for PSDT matrix. As a result, a stabilization diagram containing the information of frequency, damping ratio and mode shape can be constructed to separate the stable system poles. Furthermore, the asymptotic analysis is implemented to investigate the robustness of PSDT to noise effect. The presented approach is able to maintain the benefits of PSDT and at the same time leads to an improvement of the modal parameter estimation. It is computationally efficient, simple, stable and robust to noise. A numerical example subjected to ground motion and two structures tested in the field are employed to demonstrate the efficiency and accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

A residual-based Gaussian process model (GPM) framework is proposed for finite element model updating (FEMU). The core idea of the proposed method is that GPM is adopted to characterize the relationship between the residual and the selected parameters. Within the residual-based GPM framework, the powerful variance-based global sensitivity analysis can be analytically implemented for parameter selection, and the rate of convergence of the optimization process is accelerated substantially by providing the analytical gradient and Hessian information. A real-world arch bridge is presented to illustrate the proposed residual-based GPM framework and verify its feasibility in FEMU. [ABSTRACT FROM AUTHOR]

Hongqi Viaduct, a multi-span simply-supported bridge in Zhuzhou city, Hunan Province, China, collapsed progressively during the mechanical demolishing of the bridge on May 17, 2009. Totally nine spans collapsed in the accident and it is a typical domino-type progressive collapse. The accident resulted in the loss of 9 lives and 16 injuries. Investigations were conducted after the accident to determine the cause of the unexpected progressive collapse. This paper is aimed at presenting a summary of the bridge before and after the incident, the demolishing plans and field investigations after the accident. To better understand the cause and mechanism of the progressive collapse, a numerical simulation is carried out. A detail 3D finite element (FE) model is developed by using the explicit FE code LS-DYNA. The bridge components including the bridge slabs, wall-type piers, longitudinal and transverse reinforcement bars are included in the model. The non-linear material behaviour including the strain rate effects of the concrete and steel rebar are considered. The model is used to simulate the bridge collapse induced by demolishing, and the domino-type progressive collapse of the bridge is clearly captured. Based on the numerical results, the reason for the failure is discussed and better understood. Finally, the possible mitigation methods of such progressive collapses of multi-span viaducts are suggested. [ABSTRACT FROM AUTHOR]

Abstract: A method based on the wavelet ridges of continuous wavelet transform is proposed for the instantaneous frequency identification of time-varying structures. To eliminate noise effect, a penalty function is imposed first, and then the dynamic optimization technique is implemented for wavelet ridge extraction. The instantaneous frequencies are then identified from the extracted wavelet ridges. To validate the proposed method, a numerical example of a two degree-of-freedom spring–mass–dashpot system with time-varying stiffness is studied. The numerical results indicated that the proposed method is efficient in extracting wavelet ridges and tracking the instantaneous frequencies of the time-varying system even the numerical responses are contaminated by 10% Gauss white noise. An experiment on the cable with varying tension force is set up in the laboratory. The time-varying natural frequency is achieved by applying linear and sinusoidal varying tension forces respectively. The instantaneous cable frequencies are then identified by the proposed method. The experiment results further verified that the proposed method can effectively identify the instantaneous frequencies of time-varying structures with a high accuracy. [Copyright &y& Elsevier]

Abstract: Dealing with the boundary conditions is one of the difficult problems when using wavelet function as trial function to carry out structural analysis. In this paper, the two-dimensional tensor product trigonometric Hermite wavelet that has both good approximation characteristics of trigonometric function and multi-resolution, local characteristics of wavelet is proposed as trial function, and the united formulation of elastic bending, vibration and buckling of rectangle thin plate (on elastic foundation) with different boundary conditions is derived based on the principle of minimum potential energy. Two approaches, hierarchical and multi-resolution approach, are presented to improve calculation accuracy. The impact of proposed method is discussed by different numerical examples. Due to the Hermite interpolation properties, the proposed trigonometric wavelet method can process all kinds of boundary conditions conveniently. The solution accuracy of hierarchical method can be increased steadily with raising the order of wavelet, while the solution accuracy of multi-resolution method can be improved along with increasing the scale of wavelet. [Copyright &y& Elsevier]

Abstract: To get a good electrical resistance accumulation behavior under cycle loading, the alloy content in the polycrystalline constantan is one of the key issues. Based on the principle of the orthogonal experiment design, in the paper, 8 kinds of polycrystalline constantan foils containing different levels of alloy components were prepared using the same technology. Through a series of fatigue experiments carried out in the laboratory, the foil electrical resistance change laws with the varying percentage of Ni, Mn and Fe were obtained. The obtained electrical resistance accumulation behavior was then used to determine the best alloy content combination in the polycrystalline constantan foils by statistical methods. It is demonstrated that the foil electrical resistance accumulation was enhanced with the increase in Mn percentage, but the increases in Ni and Fe percentages have the contrary effect in the studied range of alloy contents. [Copyright &y& Elsevier]

Abstract: Fast-running response surface models that approximate multivariate input/output relationships of time-consuming physical-based computer models enable effective finite element (FE) model updating analyses. In this paper, a response surface-based FE model updating procedure for civil engineering structures in structural dynamics is presented. The key issues to implement such a model updating are discussed such as sampling with design of experiments, selecting the significant updating parameters and constructing a quadratic polynomial response surface. The objective function is formed by the residuals between analytical and measured natural frequencies. Single-objective optimization with equal weights of natural frequency residual of each mode is used for optimization computation. The proposed procedure is illustrated by a simulated simply supported beam and a full-size precast continuous box girder bridge tested under operational vibration conditions. The results have been compared with those obtained from the traditional sensitivity-based FE model updating method. The real application to a full-size bridge has demonstrated that the FE model updating process is efficient and converges fast with the response surface to replace the original FE model. With the response surface at hand, an optimization problem is formulated explicitly. Hence, no FE calculation is required in each optimization iteration. The response surface-based FE model updating can be easily implemented in practice with available commercial FE analysis packages. [Copyright &y& Elsevier]

Abstract: The wavelet transform is combined with Shannon entropy to detect structural damage from measured vibration signals in this paper. Damage features such as wavelet entropy, relative wavelet entropy and wavelet-time entropy are defined and investigated to detect and locate damage. The damage identification method is examined by a numerically simulated case and two laboratory test cases. It is demonstrated that wavelet-time entropy is a sensitive damage feature in detecting the abnormality in measured successive vibration signals, while relative wavelet entropy is a good damage feature to detect damage occurrence and damage location through the vibration signals measured from the intact (reference) and damaged structures. In addition, the relative wavelet entropy method is flexible in choosing the reference signal simultaneously measured from any undamaged location of the target structure. This advantage is particularly interesting in detecting the damage of existing structures because data from the intact (undamaged) structure is not required. [Copyright &y& Elsevier]

Abstract: A wavelet-based stochastic finite element method is presented for the bending analysis of thin plates. The wavelet scaling functions of spline wavelets are selected to construct the displacement interpolation functions of a rectangular thin plate element and the displacement shape functions are expressed by the spline wavelets. A new wavelet-based finite element formulation of thin plate bending is developed by using the virtual work principle. A wavelet-based stochastic finite element method that combines the proposed wavelet-based finite element method with Monte Carlo method is further formulated. With the aid of the wavelet-based stochastic finite element method, the present paper can deal with the problem of thin plate response variability resulting from the spatial variability of the material properties when it is subjected to static loads of uncertain nature. Numerical examples of thin plate bending have demonstrated that the proposed wavelet-based stochastic finite element method can achieve a high numerical accuracy and converges fast. [Copyright &y& Elsevier]

Abstract: The channel failures due to combined bending and web crippling may occur at the highly concentrated interior loading when there is no load stiffener in cold-formed thin-walled steel beams. This paper presents accurate finite element models to predict the behavior and ultimate strengths of cold-formed steel channels subjected to pure bending as well as combined bending and web crippling. Both geometric and material nonlinearities are considered in the finite element analysis. The nonlinear finite element models are verified against experimental results of cold-formed steel channels subjected to pure bending as well as combined bending and web crippling. The finite element analytical results show a good agreement with the experimental results in terms of the ultimate loads and moments, failure modes and web load-deformation curves thus validating the accuracy of the finite element models. The verified finite element models are then used for an extensive parametric study of different channel dimensions. The channel strengths predicted from the parametric study are compared with the design strengths calculated from the North American Specification for cold-formed steel structures. It is shown that the design rules in the North American Specification are generally conservative for channel sections with unstiffened flanges having the web slenderness ranged from 7.8 to 108.5 subjected to combined bending and web crippling. It is demonstrated that the nonlinear finite element analysis by using the verified finite element models against test results is an effective way to predict the ultimate strengths of cold-formed thin-walled steel members. [Copyright &y& Elsevier]

Abstract: Most of vibration-based damage detection methods require the modal properties that are obtained from measured signals through the system identification techniques. However, the modal properties such as natural frequencies and mode shapes are not such a good sensitive indication of structural damage. The wavelet packet transform (WPT) is a mathematical tool that has a special advantage over the traditional Fourier transform in analyzing non-stationary signals. It adopts redundant basis functions and hence can provide an arbitrary time-frequency resolution. In this study, a damage detection index called wavelet packet energy rate index (WPERI), is proposed for the damage detection of beam structures. The measured dynamic signals are decomposed into the wavelet packet components and the wavelet energy rate index is computed to indicate the structural damage. The proposed damage identification method is firstly illustrated with a simulated simply supported beam and the identified damage is satisfactory with assumed damage. Afterward, the method is applied to the tested steel beams with three damage scenarios in the laboratory. Despite the noise is present for real measurement data, the identified damage pattern is comparable with the tests. Both simulated and experimental studies demonstrated that the WPT-based energy rate index is a good candidate index that is sensitive to structural local damage. [Copyright &y& Elsevier]

Abstract: Vibration-based structural health monitoring usually needs to extract vibration characteristics from operational vibration measurements. The stochastic subspace identification (SSI) algorithm is an advanced technique for performing such an operational modal analysis. A newly developed signal processing technique, called empirical mode decomposition (EMD), is capable of dealing with non-stationary signals. An EMD-based stochastic subspace identification procedure utilizing operational vibration measurements is presented in this paper. The output-only measurements are first decomposed into modal response functions by means of the EMD technique, on the basis of specified intermittency frequencies. The stochastic subspace identification method is then applied to the decomposed signals to yield the modal parameters. A case study of the operational measurements from a real bridge is presented, in order to illustrate the applicability of the proposed technique. It is demonstrated that the stable pole in the stabilization diagrams becomes unique and the vibration characteristics are easily identified for the decomposed signals, bypassing the influence of other modal components and fake frequencies due to unwanted noise. [Copyright &y& Elsevier]

Abstract: A baseline finite element model is a reference in structural damage detection and long-term health monitoring. An ambient vibration measurement based procedure is presented to develop such a baseline model for a newly constructed Qingzhou cable-stayed bridge over the Ming River, Fuzhou, China. A 605m main span of the bridge is currently the longest in the world among all completed composite-deck cable-stayed bridges. The procedure includes several tasks: finite element modeling, field ambient vibration testing, parametric studies and model validation. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of large span cable-stayed bridges with a low range (0–1.0Hz) of natural frequencies of interest. Some important issues in the modeling of such a complicated bridge, such as the initial equilibrium configuration due to dead load, geometrical nonlinearities, concrete slab, the shear connection of the composite deck, and the longitudinal restraints of the end expansion joints, have been clarified. The developed three-dimensional finite element model of the bridge has achieved a good correlation with the measured natural frequencies and mode shapes identified from field ambient vibration tests. [Copyright &y& Elsevier]

Abstract: An analytical and experimental modal analysis has been carried out on the Qingzhou cable-stayed bridge in Fuzhou, China. Its main span of 605 m is currently the longest span among the completed composite-deck cable-stayed bridges in the world. An analytical modal analysis is performed on the developed three-dimensional finite element model starting from the deformed configuration to provide the analytical frequencies and mode shapes. The field ambient vibration tests on the bridge deck and all stay cables were conducted just prior to the opening of the bridge. The output-only modal parameter identification is then carried out by using the peak picking of the average normalized power spectral densities in the frequency-domain and stochastic subspace identification in the time-domain. A good correlation is achieved between the finite element and ambient vibration test results. It is demonstrated that the analytical and experimental modal analysis provide a comprehensive study on the dynamic properties of the bridge. The ambient vibration tests are sufficient to identify the most significant modes below 1.0 Hz of this kind of large span cable-stayed bridge. The validated finite element model with respect to ambient vibration test results can serve as the baseline for a more precise dynamic response prediction and long-term health monitoring of the bridge. [Copyright &y& Elsevier]

An ambient vibration-based seismic evaluation procedure of a three span continuous girder bridge is presented. The procedure includes field ambient vibration testing, finite element (FE) modeling, selection of earthquake ground motion, time history analysis and seismic safety evaluation of the bridge. Ambient vibration tests were carried out to determine the dynamic characteristics of the bridge, i.e. eigenfrequencies, mode shapes and damping ratios. A three-dimensional FE model was calibrated based on the ambient vibration test results. The results of the seismic analysis show that a few steel members have to be strengthened and anchor bolts of bearings may fail. [Copyright &y& Elsevier]

Old temples built in ancient time in Nepal are traditional and monumental structures with historic and archaeological importance. It is now an essential issue to evaluate their seismic safety for future earthquakes. Seismic evaluation method needs the fundamental dynamic properties of the temples. In this paper, dynamic properties of selected 10 typical multi-tiered temples are obtained by using the finite element method. Three of those temples are tested by ambient vibration methods under wind-induced excitation to obtain the real dynamic properties and validate the finite element models. Based on validated finite element model from the test, an empirical formula is proposed to estimate the natural period of vibration of Nepalese temples. Seismic capacity evaluation is then performed using the seismic coefficient method. To achieve a more realistic result, 3D dynamic analysis is carried out by the response spectrum method. Results show that the masonry temples in Nepal have fundamental time period less than 0.6 s. Damping ratio lies between 1% and 6%. The most crucial parts of Nepalese temples are the piers between the openings at the base level. Most of the failure modes are associated with tensile and compressive stresses. [Copyright &y& Elsevier]

• A bridge dynamic response analysis method considering the spatial dependency of uncertain parameters. • The uncertain parameter is described by a non-probabilistic interval field model. • The spatial dependency of the interval field is quantified by the Karhunen-Loève expansion. • The proposed method significantly reduces the computational effort and improves the computational efficiency. Uncertain parameters with spatial dependency exist in actual bridges inevitably, which significantly affect the bridge dynamic response. However, such spatial dependency is often neglected when investigating its influence on bridge response. This study proposes a bridge dynamic response analysis method considering the spatial dependency of uncertain parameters. Firstly, the bridge uncertain parameter is described by a non-probabilistic interval field model, and the spatial dependency between adjacent values of the interval field is quantified by the Karhunen-Loève like expansion. Thus the bridge is transformed into a system with multidimensional interval parameters by finite element method. Then, the system with multidimensional interval parameters is decomposed into several one-dimensional subsystems with only one interval parameter. Finally, the interval parameters of each one-dimensional system are divided into several subintervals with small uncertainties, and the dynamic response is obtained by combining analysis of subinterval results. Numerical examples are used to verify the accuracy and efficiency of the proposed method, and the results indicate that the proposed method significantly reduces the computational effort and improves the computational efficiency. Higher level of spatial dependency of the interval field, larger subinterval number, and lower uncertainty level of the non-probabilistic interval field leads to higher dynamic analysis accuracy. [ABSTRACT FROM AUTHOR]

The vibration signals are usually assumed to be stationary for the sake of simplicity, but actually many signals are not definitely stationary, and ignoring the non-stationary characteristics of signals may affect the follow-up analysis directly. Therefore, proper evaluation of the non-stationarity of the analyzed signal is an inevitable and very important preprocessing procedure. In this paper, a recurrence quantification analysis-based signal non-stationarity assessment method using the recurrence plot, a time–time plane, is presented. The aiming of this method is to quantify the non-stationarity of structural operational vibration signals, and extract the non-stationary sensitive features of structural operational vibration signal from its recurrence plot. Hence various recurrence patterns in the recurrence plot are studied, of which different patterns indicate that the signals have different characters. Drift and disruption represent the signal non-stationarity. The drifted pattern means that the signal contains a trend or drift, and the disrupted pattern means that sudden changes occurred in the signal. Meanwhile, variation rules of local recurrence density in the recurrence plots caused by those non-stationarity patterns, are discussed. Afterwards, based on the variation of local recurrence density and Taguchi's quality loss function, a new non-stationarity measurement, named recurrence loss value, is proposed. Then the comparison between the existing measurement recurrence trend and the proposed measurement recurrence loss value is conducted. Results show that the recurrence trend is mainly sensitive to the drift, and the recurrence loss value is not only sensitive to the disruption but also effective to the drift. Finally, the proposed measurement is further verified by assessing the non-stationarity of structural operational vibration signals. Those examples have demonstrated that the recurrence loss value has a promising feasibility in the practical engineering application. • RP is firstly adopted to evaluate the non-stationarities in structural dynamics. • This paper presents practicable definition for forms of non-stationarity in RPs. • A novel measurement recurrence loss value is proposed for nonstationarity assessment. • Comparison with existing measurement proves that the proposed is more effective. [ABSTRACT FROM AUTHOR]

• The data of 44 articles (including data on 46,723 pigs) met the selection criteria. • The pooled prevalence of T. gondii in pigs in China was 29% (13,363/46,723). • The prevalence of T. gondii infection in pigs in different regions, and in different types, varied considerably. • Continuous monitoring the prevalence of T. gondii in pigs is necessary. Toxoplasma gondii , is one of the most important foodborne zoonotic pathogens, which can infect virtually all warm-blooded animals, including pigs, and causes severe illness in congenitally infected infants and even death in patients with AIDS. Pigs (Sus scrofa) are one of the most important intermediate hosts of T. gondii , and human transmission occurs through consumption of raw or poorly cooked pork. In this systematic review and meta-analysis, we searched Chongqing VIP, Wanfang, Chinese Web of Knowledge, PubMed, and ScienceDirect databases for published papers regarding Toxoplasma infection in pigs in China, from inception to Oct 29, 2017. Search strings included whether they reported the samples of more than 30 pigs and provided information that allowed us to establish the prevalence of Toxoplasma infection. Moreover, we excluded repeated studies, reviews, other host studies, as well as studies with inconsistent data, incomplete information, those that only provided prevalence data, and those outside of Mainland China. We extracted the numbers of pigs with Toxoplasma infection from the obtained studies, and calculated the pooled prevalence of Toxoplasma infection in the pigs using a random-effects model. The data of 44 articles (including data on 46,723 pigs) were compliant with the standards. The pooled prevalence of T. gondii infection in pigs in China was 29% (95% CI 24–34), with 25% (95% CI 18–32) in pigs sampled before 2010 and 28% (95% CI 21–36) in pigs sampled in 2010 or later. The pooled prevalence of T. gondii in pigs from Northeast China (20%, 95% CI 14–26) was significantly lower than those from other regions (North China: 40%, 95% CI 32–47; Northwest China: 32%, 95% CI 13–51; East China: 30%, 95% CI 20–41; and South China: 35%, 95% CI 26–45; Central China: 23%, 95% CI 14–31; Southwest China: 33%, 95% CI 15–52). The estimated pooled prevalence of T. gondii infection was 36% (95% CI 25–47, 8,018/21,892) in pigs tested by ELISA, 24% (95% CI 19–28, 4,304/18,608) in pigs examined by IHA, and 19% (95% CI 8–31, 1,041/6,223) in pigs detected by other methods. Moreover, 1202 of 7470 piglets were detected as T. gondii -positive, and the prevalence (17%) was lower than that in fattening pigs (25%, OR = 1.28), sows (34%, OR = 2.13), and breeding boars (35%, OR = 2.46). Our findings suggested that toxoplasmosis is common in pigs in Mainland China. It is necessary to monitor the prevalence of T. gondii in pigs, and powerful and effective regulatory measures should be undertaken to reduce human exposure to T. gondii via the consumption of pork. [ABSTRACT FROM AUTHOR]

Purpose: To prospectively evaluate safety and efficacy of biliary stent placement with iodine-125 (125I) seeds in patients with malignant obstructive jaundice (MOJ).Materials and Methods: From July 2011 to June 2014, 55 patients were enrolled (group A, 11 men and 17 women, mean age 70.93 y ± 8.58; group B, 14 men and 13 women, mean age 70.26 y ± 9.71). All patients were randomly assigned to placement of a biliary stent with 125I seeds (group A) or biliary stent only (group B). After stent placement, outcomes were measured regarding relief of MOJ. Clinical success rate, survival time, and safety were recorded. P < .05 was considered to indicate significant difference.Results: Stents were successfully placed in all 55 patients. MOJ was relieved in all patients, and there were no significant differences in complications related to stent insertion between the 2 groups. Mean and median stent patency were 191 days ± 19.8 (95% confidence interval [CI], 152-230 d) and 179 days ± 191.4 (95% CI, 87-267 d) in group A and 88.3 days ± 16.3 (95% CI, 61-114 d) and 77 days ± 88.2 (95% CI, 65-86 d) in group B (P < .001, log-rank test). Mean and median survival time were 222.6 days ± 21.0 (95% CI, 181-263 d) and 241 days ± 18.2 (95% CI, 179-270 d) in group A and 139.1 days ± 14.5 (95% CI, 110-167 d) and 142 days ± 16.3 (95% CI, 83-177 d) in group B (P < .001, log-rank test).Conclusions: 125I seeds combined with biliary stent placement could significantly improve stent patency. The procedure seems to be safe and to extend survival compared with self-expandable biliary stent placement. [ABSTRACT FROM AUTHOR]

Highlights • This paper proposes a novel two-phase damage detection method for structures under a moving load. • The proposed method utilizes both wavelet signal processing and wavelet finite element model for damage detection. • The proposed method consists of two sequential phases, namely localization and quantification. • The proposed method is successfully validates it via a laboratory experiment of a scaled beam structure. Abstract This paper proposes a damage detection method with two phases, namely, localization and quantification, for beam structures subjected to moving load and successfully validates it via a laboratory experiment. Firstly, the discrete wavelet transform (DWT) is applied to decompose the displacement response change induced by a moving vehicle and locate potential structural damages. Then adaptive-scale wavelet finite element model (WFEM) updating is employed to estimate the damage severity in the identified damage regions in a progressive fashion. The elemental scales of WFEM are adaptively changed according to not only the moving vehicle position but also the progressively identified damage regions. Such a method can effectively minimize the number of modeling degree-of-freedoms (DOFs) and updating parameters during optimization. The feasibility and effectiveness of the proposed method is examined through a laboratory experiment with different damage scenarios. The results indicate the proposed method can achieve good consistency between structural modeling, damage scenarios, and load conditions, as well as an optimal tradeoff between damage detection accuracy and efficiency. [ABSTRACT FROM AUTHOR]

Highlights • A reliable risk assessment tool under spatial varying ground motions is proposed. • The spatial variability of ground motions on the seismic risk is investigate. • Repair time of bridge under multi-support and uniform excitations are compared. • The effect of spatial variability and hazard curve on seismic risk is examined. Abstract Current probabilistic seismic risk assessment framework does not fully address the impact of the spatial variability of ground motions on long bridges. However, recent studies have highlighted that long-span bridges are more vulnerable to damage due to spatial varying ground motions. To achieve this increased vulnerability, this research presents a reliable risk assessment tool for long-span bridges subjected to spatial varying ground motions. The proposed method includes the following tasks: (i) the simulation of spatially variable ground motions, (ii) creation of numerical bridge model, (iii) generation of probabilistic seismic demand models, (iv) development of component and system fragility curves, (v) estimation of annual exceedance of damage through site-compatible hazard curves, and (vi) computation of repair time. As an illustration, a cable-stayed bridge is selected to highlight the effect of spatial variability of ground motions on the seismic risk and repair time of individual bridge components and bridge system in comparison to uniform excitations. Additionally, a sensitivity analysis is performed to examine the effect of spatial variability parameters and hazard curve-related parameters on the seismic risk of the bridge. [ABSTRACT FROM AUTHOR]

• A Domain-adversarial Neural Network based damage detection method for bridge structures. • The domain invariant feature space between the source and target domain is extracted by adversarial training. • The damage label information is transferred from the source domain to the target domain for damage detection. • The proposed method can reduce the distribution gap and achieve higher damage detection accuracy. Bridge damage detection methods based on moving load induced response and deep learning are popular, and they are effective when the training data generated by a finite element model (FEM) and the testing data measured from the actual bridge have the same distribution. However, their distributions are normally different due to the measurement and model error. This paper proposes a Domain-adversarial Neural Network (DANN) based damage detection method for bridge structures. The moving load induced displacement responses of the FEM and the actual bridge are taken as network inputs, and the feature space with the minimum differentiation between the edge distributions of the FEM (source domain) and the actual bridge (target domain) is extracted by adversarial training between the domain discriminator and the feature extractor. This feature space is a domain invariant feature of the source domain and the target domain and contains damage information only. Thus the damage label information is transferred from the source domain to the target domain for damage detection. Numerical and experimental examples manifest that the proposed method can reduce the distribution gap between the source domain and the target domain, and achieve higher damage detection accuracy than that of the traditional deep learning method by using a small number of sensors without a large amount of damage label data. [ABSTRACT FROM AUTHOR]

Mode shape curvature change has been regarded as a promising damage localization index (DLI). However, its application is limited by the requirement for high spatial resolution and reference mode shapes, and the central difference method induced low anti-noise ability. This paper aims to develop a new damage localization method by using the mode shapes extracted from moving vehicle response for beam structures without reference data. The first order mode shape with high spatial resolution in damaged state is extracted from the response measured on a moving vehicle via Hilbert transform (HT). Then regional mode shape curvature (RMSC) in damaged state which takes advantage of the high spatial resolution of mode shapes provided by moving vehicle test is defined to enhance the anti-noise ability. Subsequently the RMSC in undamaged state is estimated by the RMSC in damaged state and polynomial approximation under the assumption that RMSC in undamaged state has smooth surface. Finally an index is formulated based on RMSC before and after damage to localized damage. Numerical studies are conduced to investigate the effect of noise, moving velocity, uneven distribution of beam flexural rigidity, and road roughness on the accuracy of the proposed DLI. [ABSTRACT FROM AUTHOR]

A unified consideration of the computation of the local and global sensitivity of structural Power Spectral Density (PSD) functions for random responses is conducted utilizing the Pseudo-Excitation Method (PEM). Analytical formulae enabling the calculation of sensitivity of the first and the second order with respect to chosen parameters are derived on the basis of an efficient direct algebraic method. The analytical formulae are compact, devoid of modal truncation problem and efficient to program. Also, global sensitivity analysis is implemented analytically by incorporating Gaussian process model to provide an approximate relationship between PSD functions and the sensitive parameters. It is investigated how scattering of parameters could induce variation in response spectra from a more comprehensive viewpoint. The validity and efficiency of the presented methods are illustrated using a numerical example. [ABSTRACT FROM AUTHOR]

This paper presents a numerical evaluation of the effectiveness of shock absorber devices installed between roller bearing and stopper in reducing viaduct damage. The effectiveness of thickness and types of shock absorber devices on mitigating viaduct damage is investigated accordingly. The thickness of shock absorber devices is from 0 cm to 8 cm, with increment of 2 cm. The viaduct seismic performance is evaluated for five cases based on the thickness of shock absorber devices. In addition, three cases are studied based on the different design parameters of shock absorber devices. The three cases include viaducts with strain hardening, elastic, and strain softening shock absorber devices. Moreover, the pounding forces between roller bearing and stopper, pier damage, displacement of superstructures, relative displacement between two decks, and bending moment–curvature relationship at the pier base are evaluated. Results show that the application of thick shock absorber devices on viaducts can significantly mitigate viaduct damage. The strain softening shock absorber devices plays a more important role in reducing viaduct damage. [ABSTRACT FROM AUTHOR]

Coherence function as a fundamental measure of the degree of relationship between two time series has numerous applications in diversified fields such as financial economics, stochastic simulation and signal processing. In this study, the magnitude-squared coherence function which enables one to identify frequency-domain correlation between two time series is revisited with a view towards extracting natural frequencies directly for dynamic structural systems. This study makes a successful attempt at mathematically proving that coherence function in the modal domain converges to unit while coherence matrix converges to a matrix of ones as the frequency approaches the system poles. On the basis of these results, three new indexes incorporating the information of coherence functions or singular spectrum of coherence matrix are formulated as effective tools for natural frequency detection. A numerical example of a shear building is analyzed to illustrate the accuracy and efficiency of the proposed methods. Furthermore, a case study is performed using data measured from an operational vibration test of the Canton Tower located in China. The real application of this high-rise building demonstrates that all three new indexes proposed in this study for structural natural frequency identification can achieve satisfactory results. Compared to the conventional peak picking approach using power spectral density directly, the proposed methods are able to reduce the risk of identifying false modes. Both the simulated data and field testing data confirm the efficiency and robustness of the proposed coherence-based methods for structural natural frequency identification under operational conditions. [ABSTRACT FROM AUTHOR]

High-precision vehicle-track coupled dynamical models play a vital role in assessing the running safety of the vehicle, tracking fatigue behavior, and establishing a digital twin for high-speed railways. This study established a high-fidelity vehicle-track coupled dynamical model as a forward solver, which was then updated in a Bayesian inference framework based on the field tests of rail irregularities and wheel/rail normal contact forces. The prediction errors corresponding to different time steps were represented through a Gaussian process (GP) model characterized by a covariance function with the Gaussian kernel to incorporate the correlation between different time steps. To cope with the considerable expense of the likelihood function calculations with large-scale loop operations and the computational burden due to the large batch of repetitive evaluations of the high-fidelity forward model involved in the stochastic sampling from the posterior probability distribution, a metamodel-powered parallelizing stochastic sampling scheme was adopted. The posterior distribution could be formulated by replacing the expensive explicit model evaluation involved in the likelihood function with a Polynomial-Chaos-Kriging (PC-Kriging) predictor providing a surrogate mapping between the wheel/rail normal contact forces and physical parameters. Finally, a parallelizing computing scheme running across multiple CPU cores on high-performance computers was realized to sample from the vectorized formula of the emulator-powered posterior distribution. Field test data from a high-speed railway in China was adopted to demonstrate that the Bayesian inference scheme can quantify the uncertainties of the core physical parameters of the high-fidelity vehicle-track coupled dynamical system by efficiently trading off accuracy and computational efficiency. • A Bayesian inference scheme is proposed to update the vehicle-track dynamic model based on the wheel-rail force measurements. • A high-fidelity vehicle-track coupled dynamic model is established as a forward solver to calculate the wheel-rail force. • A PC-Kriging-powered parallelizing sampling scheme overcomes the computational challenges of Bayesian inference. • The prediction errors are modeled as a Gaussian process to incorporate the correlation among different time steps. • The computational efficiency and accuracy are verified by a field test study. [ABSTRACT FROM AUTHOR]

Investigating the bridge dynamic characteristics under operational traffic load is critical for bridge health monitoring. As vehicles traverse the bridge, the bridge frequencies present time-varying characteristics owing to the effect of vehicle-bridge dynamic interaction. The recently introduced variational nonlinear chirp mode decomposition (VNCMD) demonstrates significant benefits in identifying structural instantaneous frequencies (IFs) from the measured responses. However, its practical application is limited by the requirement for artificially setting priori parameters (i.e., upper bound of noise level and number of modal components). In this study, a modified VNCMD (MVNCMD) is proposed to overcome this limitation and is employed to identify the IFs of the bridge under moving vehicle using single sensor data. First, by modifying the optimization function, the proposed MVNCMD adopts a novel algorithm framework that eliminates the necessity for presetting the upper bound of noise level. An autoregressive spectrum-based method is then introduced to preset the number of modal components. The proposed MVNCMD is evaluated using a synthetic non-stationary signal, demonstrating its effectiveness in identifying IFs and overcoming the limitations of the original VNCMD. Furthermore, the numerical simulation involving different parameter analysis and laboratory experiments of the coupled vehicle-bridge system are conducted to validate the effectiveness of the proposed method. It is to be shown that the proposed MVNCMD method is capable of identifying the IFs of the bridge under moving vehicle using single sensor data and outperforms other time-frequency methods in terms of identification accuracy, which provides a robust tool for analyzing the time-varying characteristics of the vehicle-bridge interaction system. • Novel time-frequency method for time-varying characteristics analysis of bridge under moving vehicle with limited sensors. • Modified VNCMD for overcoming the difficulty of presetting priori parameters of original VNCMD. • Numerical simulation and laboratory experiments for demonstrating the effectiveness of the proposed method. • Discussing the effects of vehicle mass, vehicle speed, and road surface roughness on bridge frequencies. [ABSTRACT FROM AUTHOR]

Bridge structures are vulnerable to severe damage in previous earthquake events. Meanwhile, the earthquake-induced site liquefaction can significantly affect the seismic performance of bridge structures. Seismic fragility analysis is considered as an effective approach for evaluating seismic performance of bridge structural systems exposed to seismic hazards. This study aims to assess seismic fragility of a ground-bridge structure system considering site liquefaction. Based on the probabilistic seismic demand model (PSDM) and joint probabilistic seismic demand model (JPSDM), a holistic framework for fragility analysis considering site liquefaction is proposed to derive the liquefaction fragility as well as the structural system fragility. The system fragility surfaces obtained by the proposed method can reflect the influence of site properties on the damage exceeding probability of bridge structures. The results demonstrate an increasing probability of undergoing high-level damage states for the whole system containing highly loose sand under strong earthquakes, which may provide significant basis for probabilistic-based aseismic design. • A holistic framework for assessing structural system seismic fragility is proposed. • Site liquefaction fragility is assessed using a practical liquefaction severity index. • Pushover analysis is utilized to determine the structural damage bound limits. • Seismic fragility for both structural components and system is fully explored. • Influence of site liquefaction on structural system fragility is explored. [ABSTRACT FROM AUTHOR]

This paper proposes a new nonlinear structural model updating method based on the instantaneous frequencies and amplitudes of the decomposed dynamic responses under forced vibration. The instantaneous frequencies and amplitudes of the decomposed mono-component are first extracted by analytical mode decomposition (AMD) and Hilbert transform. Then, an objective function based on the residuals of instantaneous frequencies and amplitudes between experimental structure and nonlinear model is created for calibration of the nonlinear model. In this paper, the structural nonlinear properties are simulated by using hysteresis material parameters of Bouc–Wen model, and the optimal values of the hysteresis parameters are obtained by minimizing the objective function using the simulated annealing global optimization method. To validate the effectiveness of the proposed method, a three-story nonlinear shear type structure under earthquake and harmonic excitations is simulated as a numerical example. Then, the proposed method is verified by the shake table test of a real high voltage switch structure under forced vibration. The updated nonlinear structural model is further evaluated by the shake table test of the switch structure subjected to a new severe excitation. Both numerical and experimental results have shown that the proposed method can effectively update the nonlinear model and the updated model can be further used to predict the nonlinear responses due to new severe excitations. [ABSTRACT FROM AUTHOR]

• Temperature tests are conducted in a large environmental simulation test system. • Two 1:4 scaled models of five CRTS Ⅱ slab tracks with two boundary conditions. • Temperature, stress and displacement increase nonlinearly with temperature increase. • Temperature, stress and displacement decrease linearly with temperature decrease. • The constraint condition accelerate the temperature and temperature gradient. • Constraint condition decelerate temperature transfer from track slab to CAM layer. The environmental temperature plays an important role in thermal performance of materials and structure in CRTS Ⅱ ballastless slab track under operational condition. In this paper, two 1:4 geometric scaled models of five CRTS Ⅱ slab tracks on a simply-supported box girder under three environmental temperatures rising and dropping cases were conducted in a large-scale environmental simulation testing chamber, respectively. In order to study the effect of constraint conditions on the bond of cement asphalt mortar (CAM), the internal temperature distribution, stress and displacement of two scaled models with constraint and freedom boundary conditions are also compared. Results show that the internal temperatures, longitudinal stresses and displacements of the track structure increase nonlinearly within an increase of the environmental temperature. Accordingly, these same responses decrease linearly within a temperature decrease. Most importantly, when the environmental temperature variation is + 26.5℃, the testing axial force at the two ends of the prototype track structure reaches 2,849kN, and the relative longitudinal displacement between the track slab and base plate become larger with a decrease of the environmental temperature, especially for the lowest temperature of −20℃. Moreover, fixed constraint condition decelerates the temperature transfer of the track slab to CAM, since it leads to the larger absolute temperatures and stresses of the track structure compared to the free constraint. [ABSTRACT FROM AUTHOR]

• A method is proposed for damage identification under nonstationary excitations. • UARDM is a new type of RP that represents dynamic characteristics of the structure. • Multi-label CNN model decouples the identification of damage locations and levels. • The proposed method performs with higher identification accuracy and efficiency. Civil engineering structures inevitably suffer from nonstationary ambient excitations in practice, which make conventional damage identification methods relying on the stationary assumption ineffective. This study presents a novel method based on unthresholded assembled recurrence distance matrix (UARDM) and multi-label convolutional neural network (CNN) for structural damage identification under nonstationary excitations. UARDM is a new type of recurrence plot (RP) that is proposed to integrate information of multiple channels and dispense with the artificially selected threshold. It reveals intrinsic dynamic characteristics of the structure using its vibration responses from the perspective of global probabilistic autocorrelation. After that, CNN is applied to automatically extract damage-sensitive features of UARDMs and classify them for the identification of damage cases. Instead of the traditional single-label CNN model that labels each combination of damage location and level as an objective class, the multi-label CNN model is developed to decouple the identification processes of damage locations and levels in order to improve the identification accuracy and computational efficiency. It evaluates the damage level at each location through a sub-branch with an independent set of labels and detects the damage locations by fusing information of all the sub-branches. A comprehensive comparison was conducted among single-label and multi-label CNN models input with raw accelerations, unthresholded multivariate recurrence plots (UMRPs), unthresholded recurrence plots (URPs) and UARDMs through numerical simulation and experimental test. It was demonstrated that the proposed structural damage identification method based on UARDM and multi-label CNN was able to identify multiple damage locations and levels under various stationary and nonstationary excitations with higher accuracy, efficiency and robustness, and even able to detect multiple-damage cases that were not measured beforehand and involved in the training dataset. [ABSTRACT FROM AUTHOR]

A layerwise (zigzag) finite element formulation is developed for the buckling analysis of stiffened laminated plates. The laminated plate is discretized into layers along the thickness direction. Each layer of the laminated plate is modeled by the degenerated shell elements, and the stiffener is modeled by the general 3-D beam elements. Layers are stacked together according to the interlayer continuity. In-plane displacements are considered in the derivation of geometric stiffness matrix. The advantage of the proposed model is its applicability to both thin and thick laminated plates. The significance of this study lies in the disclosure of the interaction between the lateral buckling of the stiffener and the buckling of the laminate. The inverse iteration method is adopted to extract the lowest eigenvalue corresponding to buckling. Parametric and comparative studies are conducted for different plate aspect ratios, plate thickness to length ratios, degrees of layer orthotropy, ply orientations, and stiffener depth to plate thickness ratios. [Copyright &y& Elsevier]

To investigate the structural dynamics of a container subjected to a vented hydrogen explosion, 48 field tests were conducted in a 40-foot container with roof vents and an end vent. The effects of the hydrogen concentration, ignition position, and obstacles on the evolution of the dynamic responses were investigated. Three stages were generally observed for displacements: (1) At the stage of the vent rupture, the displacement could be approximated as a quasi-static response, and there was a linear relationship between the peaks of positive overpressure and displacement. (2) Structural deformation appeared as reciprocating vibration at the stage of Helmholtz oscillation. (3) The structure exhibited relatively weak irregular fluctuation when high-frequency acoustic oscillation occurred. Two types of the structural acceleration with low and high amplitudes resulting from Helmholtz oscillation and acoustic oscillation, respectively, were clearly observed. For the end-vented explosion, multiple peaks were observed for the displacement at the quasi-static stage due to the rupture, discharge, and external explosion. Moreover, the displacement was sensitive to hydrogen concentration, whereas the number of obstacles and the ignition position had significant influences on the peak acceleration for roof venting. This work conducted the fundamental explanation for the evolution law of structural responses induced by vented hydrogen explosions from the perspective of structural dynamics and enriched the experimental accumulation in a large-scale container with congestion in this field. [Display omitted] • 48 field tests of the vented hydrogen explosion in a large-scale container were conducted. • The effects of concentration, ignition positions and obstacles on the structural dynamics were investigated. • Analysis of three stages with vent rupture, Helmholtz oscillation and high-frequency acoustic oscillation were studied. • A linear relationship between the peaks of positive overpressure and displacement was found in the stage of the vent rupture. • The evolution mechanism of structural dynamics under hydrogen explosion venting was experimentally revealed. [ABSTRACT FROM AUTHOR]

• A total of 35 papers containing 12,354 horses from 17 countries were analyzed. • The global seroprevalence of Toxoplasma gondii among horses is 11.29%. • Horses collected after 2010 has a higher seroprevalence of T. gondii than that collected before 2010. • A higher seroprevalence was observed in horses aged of more than 5 years-old. • Presence of cats in farm has positive affect on T. gondi i seropositivity. Toxoplasmosis, one of the most common zoonoses worldwide, is caused by Toxoplasma gondii. T. gondii can infect almost all warm-blooded animals, including humans. Horses are an intermediate host of T. gondii , representing a potential risk for humans. To determine the T. gondii seroprevalence in horses worldwide, a global meta-analysis was conducted. A total of 35 publications were obtained by searching the PubMed, ScienceDirect, Chinese Web of knowledge (CNKI) and Wanfang databases. A total of 12,354 horses were assessed, of which 1580 were positive for T. gondii. The pooled overall seroprevalence of horses infected by T. gondii was 11.29%. No significant difference of T. gondii seroprevalence was observed between male and female horses. The seroprevalence of T. gondii in horses from different countries varied. Our findings suggest that toxoplasmosis is prevalent in horses worldwide. Therefore, it is necessary to implement continuous monitoring of the status of T. gondii seroprevalence in horses. Moreover, powerful regulatory measures should be implemented to prevent and control the spread of toxoplasmosis. [ABSTRACT FROM AUTHOR]

• A combined method is proposed for instantaneous frequency identification. • The method combines the extended AMD, recursive Hilbert transform and zoom SWT. • It enables to provide good time-frequency representation for non-asymptotic signals. Civil engineering structures such as high-rise buildings and long-span cable-supported bridges usually exhibit low-frequency characteristics and the resultant response signals may be non-asymptotic (the amplitude change rate is higher than its phase change rate) and even have closely-spaced frequency components. The identification of satisfactory instantaneous frequencies of such response signals is a challenge faced by standard synchrosqueezing wavelet transform. The paper aims to propose a combined method to address this challenge. The proposed method combines an extended analytical mode decomposition (AMD) method, a recursive Hilbert transform and a zoom synchrosqueezing wavelet transform (consisting of frequency-shift operation and partial zoom synchrosqueezing operation). In the method, a multi-component signal, which may consist of closely spaced frequency components, is firstly decomposed into several mono-component signals by the extended AMD, and the extracted mono-components are then demodulated into asymptotic signals by recursively using the Hilbert transform. After that, a frequency-shift operation is employed to improve time resolution and a partial zoom synchrosqueezing operation is then applied to improve the frequency resolution in the narrow low frequency range of interest. Two numerical examples, an experiment on an aluminum cantilever beam with abrupt mass reduction and an experiment on a cable with time-varying tension forces are provided to illustrate the effectiveness, accuracy and robustness of the method. [ABSTRACT FROM AUTHOR]

Highlights • A Bayesian based nonlinear model updating approach is proposed. • Instantaneous amplitudes of the decomposed dynamic responses are used. • Uncertainty quantification of the model updating results due to noise is conducted. • Numerical and experimental investigations are conducted to validate the approach. • Reliable and accurate nonlinear model updating results are obtained. Abstract This paper proposes a Bayesian based nonlinear model updating approach using the instantaneous amplitudes of the decomposed dynamic responses. Uncertainty quantification of the model updating results due to the measurement noise is conducted. The residual of the instantaneous amplitudes of the decomposed structural dynamic responses between the test structure and the analytical nonlinear model is used to construct the maximum likelihood function. Since nonlinear model parameters and simulated error variances of the instantaneous parameters are all unknown, the extended maximum likelihood estimation method is used to update these parameters. The uncertainty in the updated nonlinear model parameters can be evaluated by using the Cram-Rao lower bound theorem with the exact Fisher Information matrix. A numerical study on a three-storey building structure model under earthquake excitation is performed to verify the accuracy and performance of the proposed approach. An experimental verification on a high voltage switch structure under harmonic excitation is conducted to investigate the accuracy of using the proposed approach for nonlinear model updating. Both numerical and experimental results demonstrate that the proposed approach is reliable and accurate for nonlinear model updating, with the capacity of considering the uncertain noise effect in the measurements. [ABSTRACT FROM AUTHOR]

• An improved LMSST with adaptive window width (ALMSST) method is proposed to identify the instantaneous frequencies (IFs) of time-varying structures. • The window width of ALMSST can be adaptively determined by combining AR-VMD and a window width optimization algorithm. • Numerical simulations and experiments verified the applicability of the proposed ALMSST method for IF identification of time-varying structures. Civil engineering structures usually exhibit time-varying characteristics under operational conditions due to changes in environment and loads. The identification of instantaneous frequencies (IFs) from measured responses of time-varying structures is a challenge when using the local maximum synchrosqueezing transform (LMSST) due to the difficulty in selecting the appropriate window width. In this study, an improved LMSST with adaptive window width (ALMSST) is proposed to circumvent the limitations of LMSST. The window width of ALMSST can be adaptively determined by combining the autoregressive power spectrum-based variational modal decomposition (AR-VMD) and a window width optimization algorithm. The AR-VMD is used to decompose the multi-component signal into mono-component signals. The Rényi entropy is adopted as an evaluation index in the window width optimization algorithm for selecting the optimal window width for each mono-component signal. Therefore, ALMSST can provide a highly concentrated time–frequency (TF) representation for all mono-component signals. Two simulated signals demonstrate that the ALMSST improves the accuracy of identified IFs compared with LMSST. Numerical simulation of a three-story shear building model with time-varying stiffness shows that ALMSST can accurately identify the IFs of time-varying structures under heavy noise. A cable test with linear and sinusoidal varying tension forces and a vehicle-bridge interaction (VBI) model system with different vehicle weights are investigated to verify the applicability of ALMSST to track the IFs of time-varying structures. Numerical simulation and experimental results illustrate that ALMSST performs well in identifying the IFs of time-varying structures. [ABSTRACT FROM AUTHOR]