Explore the vast range of titles available.

Short pitch corrugation has been a problem for railways worldwide over one century. In this paper, a parametric investigation of fastenings is conducted to understand the corrugation formation mechanism and gain insights into corrugation mitigation. A three-dimensional finite element vehicle–track dynamic interaction model is employed, which considers the coupling between the structural dynamics and the contact mechanics, while the damage mechanism is assumed to be differential wear. Various fastening models with different configurations, boundary conditions, and parameters of stiffness and damping are built up and analysed. These models may represent different service stages of fastenings in the field. Besides, the effect of train speeds on corrugation features is studied. The results indicate: (1) Fastening parameters and modelling play an important role in corrugation formation. (2) The fastening longitudinal constraint to the rail is the major factor that determines the corrugation formation. The fastening vertical and lateral constraints influence corrugation features in terms of spatial distribution and wavelength components. (3) The strengthening of fastening constraints in the longitudinal dimension helps to mitigate corrugation. Meanwhile, the inner fastening constraint in the lateral direction is necessary for corrugation alleviation. (4) The increase in fastening longitudinal stiffness and damping can reduce the vibration amplitudes of longitudinal compression modes and thus reduce the track corrugation propensity. The simulation in this work can well explain the field corrugation in terms of the occurrence possibility and major wavelength components. It can also explain the field data with respect to the small variation between the corrugation wavelength and train speed, which is caused by frequency selection and jump between rail longitudinal compression modes.

Railway bridges are built to allow trains to cross over highways, valleys, or other transportation infrastructure. In recent years, the number of railway bridges subjected to over-height collision forces has increased. These collisions damage the bridge and affect the safety of the running train. In this investigation, first, a 3D GT26 train-track-bridge interaction model was created to study the effects of collision forces applied to the bridge superstructure and not to the bridge piers as a novelty of this research using the finite element analysis. Then, the dynamic responses of the railway bridge due to the GT26 train load and subjected to over-height collision forces were obtained. Finally, the different sensitivity analyses describe that changing the length of the collision area, the bridge span, and the value of collision forces affect the dynamic responses of the bridge in the contact area. The results show that maximum lateral displacement of the concrete girder in case of assuming the GT26 train 3D model plus over-height collision force is 8.88% less than the case in which considering only freight train axle-load and same over-height collision force apply to the bridge superstructure, and its value reduces from 45 mm to 41 mm. The maximum lateral displacement of the bridge deck is reduced by about 71% by increasing the collision area length from 0.2 m to 1.2 m and at the impact area rises about 43.5% by changing collision speed from 48 km/hr to 144 km/hr as collision force from 7753 kN to 13370 kN.

Variable speed operation of the train cause easily the wheel-track slipping phenomenon, inducing strong nonlinear dynamic behavior of the suspended monorail train and bridge system (SMTBS), especially under an insufficient wheel-track friction coefficient. To investigate the coupled vibration features of the SMTBS under variable speed conditions, a novel 3D train–bridge interaction model for the monorail system considering nonlinear wheel-track slipping behavior is developed. Firstly, based on the D’Alembert principle, the vibration equations of the vehicle subsystem are derived by adequately considering the nonlinear interactive behavior among the vehicle components. Then, a high-efficiency modeling method for the large-scale bridge subsystem is proposed based on the component mode synthesis (CMS) method. The vehicle and bridge subsystems are coupled with a spatial wheel-track interaction model considering the nonlinear wheel-track sliding behavior. Furtherly, by a comprehensive comparison with the field test data, the effectiveness of the proposed method is verified, as well as the reasonable modal truncation frequencies of the bridge subsystem are determined. On this basis, the dynamics performances of the SMTBS are evaluated under different initial braking speeds and wheel-track interfacial adhesion conditions; besides, the nonlinear wheel-track slipping characteristics and their influences on the vehicle–bridge interaction are also revealed. The analysis results indicate that the proposed model is reliable for investigating the time-varying dynamic features of SMTBS under variable train speeds. Both the axle load transfer phenomenon and longitudinal slip of the driving tire would be easy to appear under the braking condition, which would significantly increase the longitudinal vehicle–bridge dynamic responses. To ensure a good vehicle–bridge dynamics performance, it is suggested that the wheel-track interfacial friction coefficient is larger than 0.35.

It is inevitable that metro shield tunnels undergo uneven settlement during both construction and long-term operation, ultimately leading to structural damage, intensified wheel-track interactions, and a decline in both vehicle running safety and riding comfort. Often overlooked, random track irregularities can also impact the evaluation of metro running safety and riding comfort under uneven tunnel settlement. Based on a three-dimensional vehicle-track dynamic interaction model, this paper examined the effects of random track irregularities on running safety and riding comfort indexes, taking into account various settlement wavelengths and settlement amplitudes. Results indicate that random track irregularities can have significant impacts on the running safety and riding comfort indexes under a small settlement amplitude, most notably on the train vertical acceleration.

Uneven tunnel settlement has adverse effects of varying degrees on tunnel structures, track structures, and metro train operating conditions. With increasing emphasis on the safety and comfort of metro operations, it is necessary to assess the metro running safety and comfort under uneven settlement conditions. Utilizing a vehicle-track dynamic interaction model, this paper analyzes the variations in the wheel load reduction rate, maximum vertical acceleration of the car body, and the stability index under cosine-shaped settlement curves with different settlement wavelengths and amplitudes, as well as at various running speeds. Results show that three indexes are positively correlated with the settlement amplitude under a fixed settlement wavelength, and negatively correlated with the settlement wavelength under a fixed settlement amplitude and vehicle speed. Additionally, derailment is likely to occur at a 10 m settlement wavelength.

To understand human to human dealing accurately, human interaction recognition (HIR) systems require robust feature extraction and selection methods based on vision sensors. In this paper, we have proposed WHITE STAG model to wisely track human interactions using space time methods as well as shape based angular-geometric sequential approaches over full-body silhouettes and skeleton joints, respectively. After feature extraction, feature space is reduced by employing codebook generation and linear discriminant analysis (LDA). Finally, kernel sliding perceptron is used to recognize multiple classes of human interactions. The proposed WHITE STAG model is validated using two publicly available RGB datasets and one self-annotated intensity interactive dataset as novelty. For evaluation, four experiments are performed using leave-one-out and cross validation testing schemes. Our WHITE STAG model and kernel sliding perceptron outperformed the existing well known statistical state-of-the-art methods by achieving a weighted average recognition rate of 87.48% over UT-Interaction, 87.5% over BIT-Interaction and 85.7% over proposed IM-IntensityInteractive7 datasets. The proposed system should be applicable to various multimedia contents and security applications such as surveillance systems, video based learning, medical futurists, service cobots, and interactive gaming.

Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways. They can cause significant wheel-rail dynamic interactions, leading to wheel-rail noise, component damage, and deterioration. Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities. However, the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape. In this study, novel theoretical models were developed for three categories of rail weld irregularities, based on measurements of the high-speed railway from Beijing to Shanghai. The vertical dynamic forces in the time and frequency domains were compared under different running speeds. These forces generated by the rail weld irregularities that were measured and modeled, respectively, were compared to validate the accuracy of the proposed model. Finally, based on the numerical study, the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network (ANN), and the optimum combination of parameters for this model is found. The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature. The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.

The prestressed-concrete continuous-girder bridge is one of the major high-speed railway bridges that plays an essential role in the railway. Using a typical high-speed railway continuous-girder bridge as a case study, a track-bridge longitudinal interaction model has been initially established with a comprehensive consideration of the components including rail, track slab, bed plate, rail fastener, cement asphalt mortar, sliding layer, and bridge structure. The damage states of the bridge and the seismic capacity model for key structural components of the bridge under various damages were defined. A probabilistic seismic demand model was constructed for structural components according to the incremental dynamic analysis of a suite of selected ground-motion. The fragility curves of the bridge components were derived and compared with that of the bridge model without a track system. Then, the failure probability of the bridge system was estimated using the first-order boundary method. Finally, the risk of the bridge was assessed via the numerical convolution method using both the fragility curves and seismic hazard function. The results are drawn as follows: (1) Owing to the longitudinal constraint of the track system, the dynamic characteristics of the bridge are changed; (2) A total of four damage levels occurred on the bridge pier without the track system, but only light and moderate damage levels appear due to the track constraint; (3) Under the same peak ground acceleration, the damage exceeding probability of the model without the track system is significantly greater than that with the track system; (4) Under the slight and moderate damage states, the upper and lower limits of the system fragility curves are governed by bridge pier. They are governed by the bearing with very low failure probability under the extensive and complete damage states; and (5) Within the 100-year design period, the probability that the bridge structure subject to slight and moderate damages is “occasional”, while it is “very unlikely” that the structure will suffer from the extensive and complete damages.

Abrupt stiffness variations along the railway track may increase the geometrical and mechanical defects of railway lines. The conjunction points of a railway track with concrete and ballast pavements, which are called slab-ballasted track transitions, are one of the main areas where vertical track stiffness changes sharply. Therefore, the potential benefits of a combined transition system along the slab-ballasted transition, made of an approach slab and additional rails, are studied in this paper. For this purpose, a vehicle-track-substructure interaction model, which included three main segments of the railway track (slab track, transition zone, and ballasted track) was programmed based on the finite element method. A test line with the mentioned combined transition system was built to measure the railway track responses through field study. Then, the three-dimensional (3D) numerical model was validated using the results obtained from the experimental tests. Afterwards, a number of parametric studies were performed to analyze the dynamic responses of the combined transition zone. The results indicated that this type of transition system promotes a smoother stiffness transition between the slab track segment and the ballasted track segment by making the transition in three gradual steps. The track displacements in the analyzed case-study gradually increased by about 22%, 28%, and 34% along the combined transition zone in the junction points of the slab and ballasted tracks.

Based on the dynamic receptance method, a vehicle–track–bridge interaction model was developed to calculate the wheel–rail interaction forces and the forces transmitted to the bridge in an elevated urban rail transit system. A prediction model integrating the finite element method–boundary element method (FEM-BEM) and the statistical energy analysis (SEA) method was established to obtain the noise from the main girder, track slab, and wheel–rail system for elevated urban rail transit. The calculated results agree well with the measured data. Thereafter, the noise radiation characteristics of a single source and the total noise of elevated urban rail transit systems with resilient fasteners, trapezoidal sleepers, and steel spring floating slabs were investigated. The results demonstrate that the noise prediction model for elevated urban rail transit that was developed in this study is effective. The diversity of track forms altered the noise radiation field of elevated urban rail transit systems significantly. Compared to monolithic track beds, where the fastener stiffness is assumed to be 60 × 106 N/m (MTB_60), steel spring floating slab tracks (FSTs), trapezoidal sleeper tracks (TSTs), and resilient fasteners with a stiffness of 40 × 106 N/m (MTB_40) and 20 × 106 N/m (MTB_20) can reduce bridge-borne noise by 24.6 dB, 8.8 dB, 2.1 dB, and 4.2 dB, respectively. These vibration-mitigating tracks can decrease the radiated noise from the track slab by −0.7 dB, −0.6 dB, 2.5 dB, and 2.6 dB, but increase wheel–rail noise by 0.4 dB, 0.8 dB, 1.3 dB, and 2.4 dB, respectively. The noise emanating from the main girder and the track slab was dominant in the linear weighting of the total noise of the elevated section with MTBs. For the TST and FST, the radiated noise from the track slab contributed most to the total noise.