Abstract:To boost the operational efficiency of parallel flow intersections and further eliminate the conflict between left-turn non-motor and straight-through motor vehicles, a control strategy for non-motor vehicle crossing was proposed and then integrated with motor vehicle crossing and pedestrian crossing into a unified optimization model. Considering the constraints such as signal phase sequence, green light timing, cycle length, capacity of the waiting area for leftk-turn non-motor vehicles, clearance time of non-motor vehicles, and lane balance, the linear programming optimization model was constructed so as to maximize traffic capacity. Results show that two-step street crossing and optimization design could both solve the crossing problem of left-turn non-motor vehicles, which are effective alternative design schemes for non-motor vehicle crossing at parallel flow intersections. Compared with conventional design, the two-step street crossing reduced the motor vehicle delay by 35.02% and 55.52% respectively in high and low traffic flow scenarios, while the optimization design reduced it by 42.71% and 65.60% respectively. The two-step street crossing caused a significant increase in left-turn non-motor vehicle delays, so it is not applicable when the flow of left-turn non-motor vehicles is high. The maximum motor vehicle traffic volume of conventional design was most affected by the flow of left-turn non-motor and straight-through motor vehicles. It indicates that avoiding the conflicts between left-turn non-motor vehicles and straight-through vehicles plays a significant role in improving the traffic capacity at intersections, which can be helpful for promoting the development of green travel.

Abstract:To analyze the reasons for the fracture of fastener clips in high-speed railway operating lines, SKL15 clips were studied as the object using a method of combining field test and simulation analysis. First, an on-site investigation of rail corrugation and vibration response characteristics of clips was performed. Then, a finite element model of the fastening system was established. The modal characteristics of the clips in their free and assembly states were analyzed, and a harmonic response analysis was carried out based on the modal superposition method. The reliability of the model was proved by comparing the field test results with the simulation results. Finally, in combination with the test results and the railway operation situation, the fracture causes of the fastener clips were analyzed, and remedial measures were put forward. Results showed that the main reason for the fracture of clips was that the load frequency excited when the train passed through the corrugation section with a significant wavelength of 50-60 mm at a speed of 120 km/h was very close to the modal frequency (550–650 Hz) of the clips in the assembly state, which caused the clips to have a strong resonance effect and resulted in the significant increase in the stress at the heel end of the clips, and eventually, fatigue damage. As a result, some solutions were put forward, such as rail grinding, train speed adjustment, and clip structural optimization.

Abstract:Due to the complex profile of a bridge girder with several corners, the flow around its section exhibits obvious flow separation and reattachment phenomena. It is necessary to assess how atmospheric turbulence affects aerodynamic force. A segment model pressure wind tunnel test was carried out, and the mean and fluctuating pressure distributions in a uniform wind field and three grid-generated wind fields were obtained. The changes in the aerodynamic forces were evaluated, and the effects of turbulence on flow separation and reattachment phenomena were analyzed. Results showed that turbulence significantly changed the separation and reattachment characteristics of the section at the leading edge (especially the upper surface at zero and positive attack angles and the lower surface at negative attack angles), which in turn affected the aerodynamic characteristics of the bridge section. As the turbulence intensity increased, the amplitude of the mean pressure coefficient at the separation point near the leading edge increased, while the reattachment point moved upstream. The influence of turbulence intensity on separation and reattachment became more noticeable with the increase in the wind attack angle. The force coefficient was more affected by turbulence intensity at a high attack angle than at a small attack angle, mostly because of the pressure changes at the leading edge.

Abstract:In order to investigate the ground vibration induced by the operation of high-speed trains during earthquakes, a seismic load input formula in the frequency domain was derived based on the equivalent load method, and the equivalent linearization method was adopted to describe the nonlinear response of soil. On the basis of the two-and-a-half-dimensional finite element method (2.5D FEM) of ground vibration under high-speed train load, a 2.5D finite element model of nonlinear layered ground under combined seismic and high-speed train loads was established. The effects of vehicle speed and soil stiffness on the layered ground vibration under combined loads were analyzed. Results showed that the ground vibration displacement at the center of the track caused by seismic and high-speed train loads increased with the increase in vehicle speed, and it decreased with the increase in the stiffness of ground soil under the same vehicle speed. There was a low-frequency amplification effect for ground vibration under the joint effect of earthquake and high-speed train loads, which was more obvious for higher speed and softer ground. The medium- and high-frequency ground vibration induced by combined loads was mainly affected by the train load. The ground vibration near the center of the track was greatly affected by the combined action of seismic and high-speed train loads, while that far away from the center of the track was mainly affected by the seismic load and less affected by the high-speed train load.

Abstract:In view of the problem that it is difficult to realize fault isolation when using the analytical redundancy relations-based fault diagnosis (ARRBFD) method, this paper presents a dual improved particle filter method for fault isolation. The method employs the joint estimation model composed of state and parameter estimation particle filters to jointly estimate the values of system state and potential fault parameter, and it achieves fault isolation by comparing the estimated value of the potential fault parameter with its nominal value. In the joint estimation model, on the basis of the traditional random perturbation method, an improved random perturbation method was developed to realize the parameter time update, which uses the maximum likelihood estimation method to obtain the parameter time update gradient. Then, a sampling method was proposed to improve the sampling particle quality, which takes into account the current measured values in the sampling process and introduces the idea of particle swarm optimization and simulated annealing optimization. Simulation results show that under the two types of parametric faults assumed in this paper, the joint estimation model based on dual particle filter outperformed the joint estimation model based on extended state space in terms of robustness, calculation speed, and estimation accuracy. The proposed method significantly improved the estimation performance in the joint estimation model based on the dual particle filter. In conclusion, the proposed method meets the requirements of computational efficiency and estimation accuracy for parametric fault isolation, and it can realize the fault isolation when applying the ARRBFD method.

Abstract:The experimental study of infrared radiation and hot air collaborative heating of asphalt pavement was conducted, and the influence of coupling of different heating factors on the effect of road heating was analyzed. On the basis of analyzing the mechanism of collaborative heating on asphalt pavement and considering the specific requirements of the experiment, an experimental platform was designed and a simulation model of collaborative heating of asphalt pavement and experimental platform was established. With the aid of CFD simulation software for simulation analysis, the structural design and heating performance simulation analysis of the collaborative heating experimental platform were carried out. Results showed that the designed experimental platform could evenly distribute the hot air within the heating distance and wind speed range required for the collaborative heating experiment. The collaborative heating plate could evenly heat the road surface when the heating distance was adjusted. The hot air generator could continuously provide hot air with stable and controllable temperature and wind speed for the heating experiment. The results verified that the heating performance of the experimental platform meets the requirements of the collaborative heating experiment under multi-factor coupling, which provides a theoretical basis for the design and manufacture of collaborative heating experimental platform and the development of the collaborative heating device for thermal regeneration of asphalt pavement in the future.

Abstract:To reduce the vibration hazard of adjacent buildings caused by metro operations, a vibration reduction method of thickening the base floor of raft foundation buildings was proposed, and the vibration reduction effect of the thickened floor was studied. The three-dimensional model of “tunnel-soil-building” was established, and the model and vibration source load were verified using measured data and empirical formula. The vibration reduction effect of the thickened base floor of raft foundation building under the conditions of ordinary track bed, elastic long sleeper track bed, and steel spring floating slab track bed was examined. The influence of the horizontal distance between the building center and the metro tunnel center on the vibration reduction effect of the thickened floor was analyzed. Results showed that the thickened raft foundation effectively consumed the vibration energy caused by metro, reducing the vibration response of adjacent buildings. When the damping track bed was employed in the metro line, the damping effect was weakened to a certain extent. The vibration reduction effect of the thickened base floor was related to the horizontal distance between the building and the tunnel centerline. The closer the distance was, the better the vibration reduction effect was. Finally, a prediction method for quickly calculating the vibration reduction effect of the thickened base floor of raft foundation building was proposed, which can provide a reference for practical engineering.

Abstract:To optimize the train planning for through operation of urban rail transit, the operation organization method of through operation was analyzed, the passenger flows under through operation mode were classified, and a method of calculating the imbalance coefficient of the maximum load was proposed. A train planning optimization model for the through operation of urban rail transit was established by considering multi-group train operations and the imbalance of the load factor. The objective of this model was to minimize the travel cost of passengers, the operation cost of enterprises, and the imbalance coefficient of the load factor. Three decision variables, the location of turn-back stations, the frequency of different routing trains, and the formation of train groups, were solved by a hybrid coding genetic algorithm. Taking the Beijing Metro Fangshan Line and Line 9 as an example, the train planning optimizations for peak and off-peak hours were studied. The operational indicators such as load factors under through operation mode and independent operation mode were compared and analyzed. The effects of different objective weights on the optimal solution and optimization results were investigated. Results showed that during peak hours, compared with the independent operation mode, the optimization effect of the through operation mode was improved by 12.85% without changing the train formation plan. During off-peak hours, the multi-group train operation significantly improved the balance of the load factor. Through weight analysis, it was found that with the decrease in passenger service level weight and the increase in operating enterprise cost weight, the frequency of through trains decreased, the section of through operation gradually declined, and the effect of through operation steadily deteriorated.

Abstract:In view of the limitation of the traditional anti-drop-beam devices of railway bridges, a new corrugated steel energy dissipation anti-drop-beam device was developed for railway bridges in high earthquake intensity areas. The formula for calculating the mechanical properties of corrugated steel energy dissipation anti-drop-beam device was deduced and established. A simplified design method of energy dissipation anti-drop-beam device for railway bridges was proposed, and the design and analysis software of the device was developed. The mechanical performance test of the energy dissipation anti-drop-beam device was carried out. Taking a typical long-span continuous beam in an eight-degree earthquake intensity region of Chongqing-Kunming high-speed railway as the research object, the energy dissipation anti-drop-beam device of the bridge was designed, and the impact of the device on the seismic performance of the bridge was analyzed. Results show that the design method and mechanical parameter calculation theory of the new energy dissipation anti-drop-beam device had strong adaptability and high calculation precision, which met the accuracy requirement of engineering applications. The hysteretic curve of the anti-drop-beam device was full, the energy dissipation ability was enhanced, and the low cycle fatigue performance was good. The designed energy dissipation anti-drop-beam device could meet the seismic performance requirements of high-speed railway long-span bridges, with good effect of shock absorption and energy dissipation, which could reduce the end displacement of long-span continuous girder bridge by about 25%.

Abstract:In order to improve the accuracy of short-term traffic flow prediction, an improved traffic flow predicting model was proposed by using the adaptive beetle antennae search (BAS) algorithm to optimize the radial basis function (RBF) neural network. This was done in consideration of the drawbacks of the traditional RBF neural network model for short-term traffic flow prediction, such as fixed center value and vulnerability to drift data interference. In this model, the adaptive step size was utilized to improve the iteration speed and optimization ability of BAS algorithm. The center of the RBF hidden layer was determined based on the DBSCAN cluster, and thus the neural network structure was optimized. Traffic flow datasets were collected from real road network for training, and the proposed model was compared with widely-used models, such as BP neural network, RBF neural network, and generalized RBF neural network. Results showed that in comparison with the BP neural network, the proposed method reduced the mean absolute error by 1.87, the mean absolute percentage error by 15.96, and the root mean square error by 3.24%; the fitting degree of the proposed method was improved by 3.96%. In comparison with the generalized RBF neural network, the proposed method reduced the mean absolute error by 1.36, the mean absolute percentage error by 5.01, and the root mean square error by 2.19%; the fitting degree of the proposed method was improved by 2.5%. The proposed short-term traffic flow prediction model can provide accurate predictions for intelligent traffic guidance.

Abstract:Based on the visibility detection principle, this paper aims to enhance the accuracy for highway visibility detection in foggy weather through improving the existing dark channel prior algorithm by considering the atmospheric transmittance intensity, transmittance, atmospheric extinction coefficient, and the actual distance from a point in the image to the camera. Firstly, the problem of reconstructing 2D scene to 3D scene on the highway was solved by combining the rectangular area ranging and the actual scene object size. The K-means clustering algorithm was used to obtain the point with the minimum depth of field on the dividing line of the video image. The actual distance from the point to the camera was obtained by using the constructed ranging model. Secondly, in view of the deficiency of the traditional dark channel prior theory in solving the atmospheric transmittance intensity, a local entropy method based on image segmentation was proposed to obtain the atmospheric transmittance intensity. Then, the transmittance was obtained by using the dark channel prior theory, and the visibility was calculated by the visibility detection principle. Finally, according to the video image of K113+000 of Rilan Highway in foggy weather, the improved dark channel prior algorithm was compared with the traditional dark channel prior algorithm experimentally, and the results were referenced to the detection results of visibility detector. Results showed that when the actual visibility was about 100 m, the mean relative error (MRE) detected by the improved algorithm was 6.25%, which was 2.38% less than that of the traditional algorithm. When the actual visibility was about 150 m, the MRE detected by the improved algorithm was 6.17%, which was 3.06% less than that of the traditional algorithm. When the actual visibility was about 200 m, the MRE detected by the improved algorithm was 5.71%, which was 3.41% less than that of the traditional algorithm. With the increase in light intensity, the improved dark channel prior method has higher detection accuracy and can better adapt to the highway in daytime foggy weather.

Abstract:To promote the application of reliability analysis (probabilistic geometric design) in highway safety design and crash prediction, this paper develops crash prediction models to establish the relationship between the multi-mode failure probability of cars and car crashes. Firstly, considering the multi-mode failure as the breakthrough point, a multi-mode failure system was established based on three possible failure modes (skidding, rollover, and insufficient sight distance) of single-car on combination sections of vertical and horizontal curves. Then, 10 241 single-car crashes on the combination sections of vertical and horizontal curves of highway in Washington were taken as the research objects, and the multi-mode failure probability of the system was solved by Monte Carlo and wide bound method. Finally, three crash prediction models including negative binomial model, random effects negative binomial model, and random parameters negative binomial model were developed by taking multi-mode failure probability and road factors as explanatory variables. Moreover, the relationship between multi-mode failure probability and single-car crashes was explored. Results show that among the three models, the random parameters negative binomial model outperformed the other two models. When the multi-mode failure probability was considered, the influence of road geometric factors on the single-car crashes was weakened. Except for two exposure variables, the multi-mode failure probability had the greatest impact on single-car crashes. The number of single-car crashes was approximately linearly related to the multi-mode failure probability, and the intercept of the fitting curve was not 0. The results can be used in the reliability design of highway.

Abstract:In order to study the influence of freeze-thaw (FT) damage on the flexural fatigue life of self-compacting concrete, the four-point flexural fatigue tests at different stress levels were carried out on concrete beams subjected to different FT cycles, and the Weibull distribution parameters of flexural fatigue life of concrete beams were obtained by the method of moments. The prediction models for the fatigue life of concrete beams subjected to different FT cycles under different reliability probabilities were established. Results showed that the probability distribution of fatigue life for self-compacting concrete subjected to different FT cycles could be characterized by two-parameter Weibull distribution. The dispersion of fatigue life of self-compacting concrete increased with the increase in FT cycles and decreased with the increase in stress levels. On the basis of the test data, the P_f-S-N curves of self-compacting concrete were generated, which can accurately predict the flexural fatigue life of self-compacting concrete subjected to different FT cycles. The safety factor required for the fatigue life of self-compacting concrete increased with the increase in FT cycles, which indicates that for the self-compacting concrete suffering from more serious FT damage, a larger safety factor should be adopted to ensure the safe operation of the structure.

Abstract:To explore the mechanical properties of integral abutment-RC pile-soil structure, we designed and prefabricated four integral abutment-RC pile models with different pile foundation reinforcement ratios and cross-section shapes taking an integral abutment bridge in China as background. The quasi-static test of integral abutment-RC pile-soil interaction under low cyclic loading was carried out. The effects of reinforcement ratio and cross-section shape of RC pile on the mechanical properties of abutment-RC pile-soil system were mainly studied, and the soil resistance behind abutment, the soil resistance beside pile, and the distribution of pile strain and bending moment were analyzed. Results show that under the action of cyclic displacement of abutment, the distribution of soil resistance near the abutment back along the height direction changed from “triangular” distribution to “parabolic” distribution, and that away from the back of the abutment was basically in “triangular” distribution. The resistance of soil behind abutment was affected by the reinforcement ratio and section shape of RC pile, so it is necessary to increase the reinforcement ratio of RC pile or use rectangular section to improve the integrity of integral abutment-RC pile-soil system. The cumulative deformation of pile affected the distribution of soil resistance on the sides of pile, which reduced the soil resistance behind pile and increased the soil resistance in front of pile. The specimens with larger reinforcement ratio or rectangular cross-sectional RC piles were less affected by the cumulative deformation, and the integrity of abutment-pile foundation-soil structure was better. When the integral abutment-RC pile structure moved to the river span side, the distribution of pile strain and bending moment was consistent with that of traditional pile foundation. When moving to the riverbank, the maximum strain and bending moment of pile appeared at the joint between the bottom of abutment and the top of pile. Increasing the reinforcement ratio of RC pile or adopting rectangular cross-sectional RC pile can effectively reduce the strain and bending moment of pile body and improve the mechanical performance of RC pile foundation.

Abstract:The lane-changing behavior of drivers usually has a negative impact on traffic safety. In order to ensure the safety of vehicle lane-changing and prevent traffic accidents, the risk situation of vehicle lane-changing behavior should be identified. Through the systematic study of a large number of relevant publications at home and abroad, a review of vehicle lane-changing behavior was conducted from three aspects: statistical analysis of the literature, keyword visualization, and data set analysis. The research hotspots of key influencing factors of vehicle lane-changing were summarized. By reviewing the risk assessment methods of vehicle lane-changing behavior at home and abroad, the common risk assessment methods based on traffic conflict and driving intention were summarized and analyzed. Finally, the current issues and potential future directions for the risk assessment of lane-changing behavior were discussed. The existing research indicates that the research on lane-changing behavior should be combined with the characteristics of the traffic environment, and future research should focus on lane-changing models that are more universal and portable. In addition, the changes in drivers’ driving intention and lane change decision adjustment are important research directions for the future risk assessment of vehicle lane-changing behavior. Based on the development of the Internet of Vehicles, future research should consider a wider range of influencing factors, use more traffic environment data, consider the impact of heterogeneous traffic flow environments on the risk of vehicle lane-changing behavior, and conduct more in-depth risk evaluation method studies. Researchers can use vehicle telematics to better understand driving behaviors and factors leading to traffic accidents, which opens up new opportunities and challenges for the study of comprehensive evaluation methods for vehicle lane change risk evaluation.