Journal of Engineering and Thermal Sciences
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Seismic performance of beam-type covered bridge considering the superstructure – substructure interaction and bearing mechanical property
Get PDFModern covered bridges have attracted attention due to their multifaceted commercial functionalities, making them increasingly prevalent in construction projects throughout China. To investigate the seismic performance of the beam-type covered bridge, finite element models (FEMs) of conventional building structure, conventional bridge structure and covered bridge structure were established via OpenSEES. The effects of bearing mechanical properties on the seismic response of the whole covered bridge and impacts of lower bridge structure on the interlayer drift ratio of upper building, as well as influences of upper building structure on bearing displacement and pier displacement and stress were deeply explored by using (Incremental dynamic analysis) IDA method. Furthermore, the seismic performance of the covered bridge was evaluated under two levels of seismic hazards. Results indicate that under the seismic events may occur, the interaction between superstructure and substructure is adverse to the longitudinal seismic performance of the superstructure and wall pier of the covered bridge, but do not significantly impact the lateral seismic response of the superstructure. The existence of the superstructure notably reduces the displacement of bearings. Moreover, higher bearing stiffness lead to a more pronounced interlayer drift ratio within the superstructure of the covered bridge. The influence of bearings on the displacement and stress of wall piers is not affected by the superstructure- substructure interaction. This study involved the nonlinearity of the structure and the randomness of seismic actions and clarified the impacts of factors on the seismic response of the beam-type covered bridge. Finally, a reasonable layout of the bearings was proposed
Rolling bearing fault analysis based on variational mode decomposition and multiscale arrangement entropy
Get PDFRolling bearings in operation will appear nonlinear characteristics of the fault vibration signal. In the process of fault feature extraction, a single permutation entropy (PE) produces unsatisfactory results and low accuracy. In this paper, a new diagnostic method was proposed, which was based on variational mode decomposition (VMD) and multiscale permutation entropy (MPE) to diagnose and analyze rolling bearing faults, multi-scale aligned entropy features of intrinsic mode function (IMF) of faulty vibration signals were extracted, and then support vector machine (SVM) and K-nearest neighbor algorithm (KNN) were used to analyze these features, and the maximum attribution metrics were used to determine classification results. The test results show that this method can improve the detection accuracy by comparing with other test analysis methods
Determinated area (DA) treatment goal when treating malocclusions with jaw functional orthopedics (JFO): Contribution to scientific evidence
Get PDFOne of the goals of malocclusion treatment with Jaw Functional Orthopedics (JFO) is to obtain touch of the inferior incisors against the superior incisors in Determinate Area (DA). It is postulated that this touch would bring better stimuli and consequently faster results. Surface electromyographic study of the muscles was performed in Masseter, Temporal and suprahyoid muscles bilaterally from 159 patients undergoing malocclusion treatment with functional orthopedic appliances (FOA). To record muscle electric activity were used a conditioning signal module from Lynx Electronics Ltda with 8 channels, model EMG1000; software AqDAnalysis 4,18 from Lynx Electronics Ltda.; Software Lynx BioInspector 1,8r; passive surface electrodes (Ag/AgCl) from Noraxon Dual Electrodes (USA); dischargeable reference electrodes Kendall Meditrace (Ag/AgCl) – Canada. Frequency calibration was 2000 Hz, with 2048 sample by channel and time 1,024 seconds, and filters regulation was 20 Hz and 1000 Hz. The results found prove that there is a better electromyographic activity (bilaterally balanced) of the studied muscles when there is touch on DA. Conclusion. Touch in DA improves the neuromuscular response of patients treated with JFO. sEMG is a trustable tool to analyze masticatory muscles function for Diagnosis, Treatment and evaluation post treatment/gained objective
Vehicle suspension based on torsion bar and elastic hinge
Get PDFThe article is devoted to the development of a vehicle suspension with a nonlinear characteristic based on a torsion bar and an elastic hinge with a given characteristic on the example of tracked vehicles for constructing oil and gas pipelines. The characteristic of the elastic hinge is such that when the existing torsion bar suspension and the elastic hinge are connected in parallel, the desired characteristic is obtained. For this non-linear characteristic in the static displacement region, low stiffness was obtained, but the total stored energy at the maximum deflection of the balance bar of the resulting suspension is greater than that of existing torsion suspensions. The smoothness of the tracked vehicles with a low stiffness of the suspension increases significantly. The calculation of vibrations of the proposed suspension under kinematic excitation was carried out. A harmonic function is considered as the trajectory of the profile; a function corresponding to a single obstacle and a function corresponding to an ascent to a ledge of a given height. The elastic hinge is a pneumatic spring moving between the guides of the design form. The force characteristic of the hinge depends on the shape of the guides and on the pressure in the air spring. The calculation of the circular shapes of the guides of the elastic hinge is given. The values of the forces arising between the pneumatic spring and the guides are determined
An improved semi-supervised prototype network for few-shot fault diagnosis
Get PDFThe collection of labeled data for transient mechanical faults is limited in practical engineering scenarios. However, the completeness of sample determines quality for feature information, which is extracted by deep learning network. Therefore, to obtain more effective information with limited data, this paper proposes an improved semi-supervised prototype network (ISSPN) that can be used for fault diagnosis. Firstly, a meta-learning strategy is used to divide the sample data. Then, a standard Euclidean distance metric is used to improve the SSPN, which maps the samples to the feature space and generates prototypes. Furthermore, the original prototypes are refined with the help of unlabeled data to produce better prototypes. Finally, the classifier clusters the various faults. The effectiveness of the proposed method is verified through experiments. The experimental results show that the proposed method can do a better job of classifying different faults
Investigation of the propagation characteristics of train-induced vibration at Guangzhou Baiyun railway station
Get PDFIn densely populated cities, the increasing popularity of railways and urban rail transit interchange hubs has led to the extensive use of land resources and raised concerns about the environment, especially the inevitable noise and vibration impact. This study aims to identify the propagation patterns of roof structure vibrations in railway complexes through experimental research, with the premise of maintaining normal train operation and safety, in order to lay a foundation for developing vibration mitigation strategies and optimizing functional layout. The results found that the train-induced vibrations are strongest at track level, but decrease as they move vertically and horizontally. Vibrations from passing trains are most noticeable within a single floor slab and beams, with minimal transmission at the base of columns
Effect of welding axial stresses on the strength of a welded pipe joint with a defect
Get PDFThe use of an integrated approach to determining the static strength of operated main pipelines with surface defects makes it possible to take into account the effect of residual weld stresses in combination with operational loads. In this case, it is important to determine the nature of the welding stress distribution for welded structures made of high-strength steels. Here, there is non-uniformity of stresses concerning magnitude and gradient, which is due to technological methods. A mathematical model of the experimental-calculation method is proposed. Such a model allows describing such stresses. A two-parameter criterion for brittle-tough fracture of a material which takes into account the influence of residual stresses is used. It is shown that the combination of residual stresses and operating loads has a significant effect on the safety factor. At the same time, conditions are possible under which compressive residual stresses have a favourable effect on the static strength of a pipeline with a defect
Prediction of concrete sulfuric acid corrosion evaluation index model based on grey system theory
Get PDFIn order to predict the impact of sulfate corrosion on concrete, based on grey system theory, GM(1,1) and GM(1, N) models were used to predict and analyze the compressive strength and relative dynamic elastic modulus of concrete under sulfuric acid corrosion. The results show that the prediction error of the GM(1,1) model for concrete sulfate corrosion attenuation is within 5 %, and the residual size test of the GM(1, N) model for concrete sulfate corrosion is within 10 %
Tensor analysis of tornadoes: a new analytical and numerical model
Get PDFThis research proposes a new mathematical formulation of tornadoes based on the theory of tensor analysis and simulation in a non-inertial dynamics framework, both in two and three dimensions. This model may show the spherical upward movement of air in a tornado without taking into account vertical convection. A tornado requires several elements, including geocentric latitude, the Coriolis effect, increased airspeed in the upper atmosphere, and increased air pressure. Computing the three-dimensional location of the tornado or hurricane, as well as the mathematical models of airflow motion and the Earth's rotation in three-dimensional (3D) space, can determine a tornado's airflow characteristics. To show tornado patterns, we employed computer software that computed motion dynamics and did numerical computations. The results of 2-D modeling and simulation indicated that the greater the initial tornado angular speed, the larger the tornado area. Three-dimensional modeling and simulation also show that tornadoes are more powerful at higher geocentric latitude angles. The novelty of this study is that this model can be used to explain tornado patterns. In our research, we combine tensor analysis, computational modeling, as well as 2D and 3D simulations for simulating tornadoes for the first time. The scientific application of this finding is that researchers at the Meteorology, Climatology, and Geophysics Agency will be able to analyze a tornado and geophysical phenomena more readily with simulations and models
JTC online comprehensive fault diagnosis method based on angle feature and linear trend feature
Get PDFAiming at the problem of incompatibility of the fault diagnosis method between JTC (Jointless Track Circuit) compensation capacitor and tuning zone, based on the amplitude envelope mathematical model of induced voltage of locomotive signal, an online comprehensive fault diagnosis algorithm for multi-compensation capacitor and tuning equipment fault was proposed. It is characterized by the angle of the tangent vector of the amplitude envelope at the compensation capacitor and the linear trend within the three compensation capacitor sections close to the transmitter when the tuning device fails, the angle feature and linear trend feature are extracted to determine the fault type. Experimental results show that the proposed algorithm can accurately detect multi-compensation capacitor faults and tuning equipment faults with high accuracy and high efficiency, especially the sudden multi-compensation capacitor faults and tuning zone unit breaking faults. The accuracy of the algorithm for JTC fault diagnosis is verified under different signal-to-noise ratio and ballast resistance fluctuation, which shows that the algorithm has strong applicability