In order to evaluate thermal effects on bridge pylons in extreme weather in Hengduan Mountain region of western China, a method was applied to a long span suspension bridge that the characteristics of the temperature field and temperature stress of the bridge pylon were analyzed, and two anti-crack strategies were investigated. First, a scheme was introduced to identify and simulate the extreme weather at the bridge based on measured data. And then the characteristics of the temperature field and the associated temperature stress of the pylon in simulated extreme weather were analyzed with the software ANSYS. Finally, two strategies were proposed to solve the issue of potential crack of the pylon under extreme weather condition, adding organic coatings or a layer of UHPC (ultra high-performance concrete) on the pylon surface. The results indicate that the pylon is at risk of cracking when the tensile stress at its surface reaches 2.19 MPa in strong cooling weather. And both strategies can effectively reduce the maximum tensile stress of the surface to a safe level. As for the strategy of adding the organic coatings, the white organic coating is more favorable; so is the layer of UHPC of 0.08 m. Compared with their budget and construction, adding white organic coating is recommended as the better anti-crack strategy for the bridge pylon in this study.

In order to study the influence of artificial crust layer formed by in-situ solidified on the pile-soil stress ratio of prestressed pipe pile composite foundation, field experiments and numerical simulation analysis were carried out based on the mud pit section of Qianqing-Binhai highway in Shaoxing. On this basis, both the stress response and deformation of prestressed pipe pile composite foundation under embankment load were studied. From the pile-soil stress ratio, the influence of artificial crust layer on the bearing performance of pile composite foundation was emphatically discussed. In addition, the influence mechanism of design parameters such as the ratio of embankment height to net distance between pile caps and the ratio of pile cap width to net distance between pile caps on the development of pile-soil stress ratio were preliminarily studied. It shows that artificial crust layer can improve the bearing capacity. Under the experimental conditions, the maximum horizontal displacement of artificial crust layer combined prestressed pipe pile composite foundation occurs 5～6 m below the ground surface, which is different from traditional composite foundation decreases gradually along the depth. The pile-soil stress ratio is between 23 and 37, which is higher than that of traditional pile composite foundation.

In order to study the relationship among the fire exposure time, the content of coarse aggregate, and the macroscopic damage of tunnel lining concrete, a thermo-mechanical coupling test device of lining concrete was independently improved according to the actual fire exposure characteristics of tunnel lining, and the damage law of concrete test blocks with 20%, 30%, and 40% coarse aggregate was studied under the load ratio constant of 28% and different fire exposure time. The results show that when there is no fire accident, no deterioration appears on the surface of the lining concrete under a small load, and the quality does not change greatly. The residual compressive strength increases. Under the action of thermo-mechanical coupling, as the fire continues, a few micro-cracks form on the surface of the test block after 0.5 h of fire exposure, and wide cracks appear on the surface after 1.0 h of fire exposure, with many small cracks distributed and some cracks crossing each other. After 2.0 h of fire exposure, the bottom surface of the test block is seriously damaged. The time and degree of fire development are crucial to the damage to the lining structure. As the content of coarse aggregate of concrete decreases, the internal temperature conduction velocity of concrete slows down; the temperature value at the same position becomes smaller, and the apparent damage increases significantly. The mass loss rate of concrete with 20% coarse aggregate can reach 8.14%, while that of concrete with 40% coarse aggregate is only 4.10%, which indicates that when the strength is the same, concrete with high-content coarse aggregate has better fire resistance.

Detecting tunnel surface cracks has been one of the important tasks for subway operators. To achieve the automatic detection of tunnel cracks, this paper proposed an automatic labeling and recognition algorithm for tunnel crack samples, which combined crack feature extraction with deep learning. The paper also established an image feature library of crack samples based on the feature of tunnel cracks and improved the structure of the deep convolution network, namely AlexNet. In addition, the paper designed a track-sliding tunnel image acquisition system and inspection vehicle and then established a dataset consisting of 4 500 crack image samples and 1 500 test images, so as to verify the feasibility and effectiveness of the algorithm. The result shows that the clarity of the collected images meets the requirements, and the designed algorithm can complete the automatic labeling of cracks. The recognition rate of the crack image dataset is 97.8%, which can verify the effectiveness of the algorithm and the acquisition system.

Box-shape profiled steel sheet is usually used as the bearing element, with external claddings and spacers together, they constitute a double-layer profiled steel sheet wall system. In order to study the influence of external cladding and spacers on the flexural behavior of box-shape profiled steel sheet, 8 double-layer profiled steel sheet composite specimens and 2 box-shape profiled steel sheet standard specimens were tested for both pressure and suction loading conditions. The influences of the stiffness of external cladding and the height of spacers on the bending capacity and flexural stiffness of the double-layer profiled steel sheet were analyzed. The test results showed that when the spacer height is 100 mm, compared with the standard specimen, the bending capacity can be increased by 27.6% and 111.3%, and the flexural stiffness by 17.3% and 56.7% for the composite specimens with external cladding type I and Ⅱ, respectively, under wind pressure loading condition; and the bending capacity can be increased by 32.1% and 77.6%, and the flexural stiffness can be increased by 29.4% and 48.1% respectively for wind suction case. When the external cladding is type Ⅱ, compared with the standard specimen, the bending capacity can be increased by 66.9% and 111.3%, and the flexural stiffness by 39.9% and 56.7% for the composite specimens with spacer height 200 mm and 100 mm, respectively, under wind pressure loading condition; and the bending capacity can be increased by 59.1% and 77.6%, and the flexural stiffness can be increased by 33.5% and 48.1% respectively for wind suction case. Thus considering the system effect of the external cladding and spacers, the bending capacity and flexural stiffness of the inner box-shape profiled steel sheet can be significantly improved, and greater stiffness of the external cladding can bring better performance. Based on theoretical analysis and Eurocode, combining with the influence of the stiffness of external cladding and the height of spacers, the global design formula of the box-shape profiled steel sheet is proposed, including system effect. The analytical results obtained using this formula coincide well with the experimental ones.

In order to study the effects of freak wave parameters on the wave force of a new dumbbell-shaped bridge structure, a series of wave flume model tests were conducted. Firstly, the influences of peak frequency, frequency bandwidth and focusing position on wave elevation time history and wave crest around the dumbbell-shaped bridge were analyzed. And the influences of the wave parameters mentioned above on the freak wave force time history and the statistical peak value were investigated. Finally, based on the classical diffraction theory, a simplified calculation method for the freak wave force spectrum on the new dumbbell-shaped bridge structure was proposed. The results show that the peak frequency, focusing positions and frequency bandwidth have little influence on the wave elevation around the dumbbell-shaped bridge structure with a small difference of less than 3%. The peak frequency and focusing positions have great influence on the freak wave force of dumbbell-shaped bridge structure. When the peak frequency increases from 0.6 Hz to 1.1 Hz, the horizontal wave force increases first and then decreases with a maximum range of 11.0%, while the vertical wave force decreases by 57.0%. When the frequency bandwidth increases from 0.5 Hz to 0.8 Hz, the horizontal wave force decreases by 2.1% and the vertical wave force increases by 5.9%. When the focusing position moves from the surge side of the structure to the back/opposite side, the change amplitude of horizontal wave force is less than 5%, and that of vertical wave force is less than 3%. The comparison of experimental data and theoretical analysis proves that the simplified algorithm based on the diffraction theory can effectively estimate the wave force spectrum of dumbbell-shaped bridge structure under freak waves.

In order to investigate the response relationship between the gas explosion mechanism and parameters such as water depth, inlet pressure, inlet volume, and connected area of dry/wet areas, a 1∶50 scale hydraulic model test system was first conducted to observe the gas explosion jetting process and analyze the variation law of pressure in the shaft. Secondly, a prediction model for the maximum jetting height of the shaft and the critical conditions of the gas explosion were established according to the definition of the gas explosion. Finally, the influences of different variables on the impact load of different baffles in the bottom of the shaft were compared. The results show that the pressure in the baffle-drop shaft fluctuates sharply during a gas explosion. On the one hand, it is caused by the release of high-pressure air mass; on the other hand, high-speed movement of the air-water mixture makes the local pressure in the shaft imbalanced, which contributes to strong fluctuation. The empirical formula established by the multiple linear regression model can effectively predict the maximum jetting height of the baffle-drop shaft. The critical condition established according to the response relationship between the gas explosion intensity and different variables can accurately determine whether a gas explosion occurs. Except for the inlet pressure, submerged state of the baffle, and measured point location, the hydrodynamic load on the baffle in the bottom of the shaft during the gas explosion is also related to the randomness of air-water mixture jetted on the baffle bottom. The maximum hydrodynamic load on the baffle bottom during a gas explosion is more than 10 times as much as the hydrodynamic load on the baffle surface under normal discharge conditions.

In order to provide a scientific basis for water seepage control and later protection research of Leshan Giant Buddha, this study conducts quantitative monitoring and sampling of water seepage and atmospheric precipitation of Leshan Giant Buddha for the first time, analyzes the source and characteristics of water seepage, and studies the weathering mechanism of sandstone combined with water chemical properties and rock composition.The study shows that groundwater is the main source of water supply to water seepage in the chest of Leshan Giant Buddha during the level and dry periods, and atmospheric precipitation is the main source of water supply during the wet period. Abundant solute compositions are found in water seepage samples, with the pH value being 7.70. Since 2009, the annual average pH value of precipitation in Leshan City is higher than 5.60 and increases year by year. Until 2015, the annual average pH value of precipitation is higher than 7.00, and the precipitation has changed from acidic to alkaline. The hydrochemical type of water seepage in the chest of Leshan Giant Buddha is carbonate-calcium-type Ⅱ and sulfate-calcium-type Ⅲ. The cation is mainly Ca^{2 +} , and the anion is SO₄²⁻ and HCO₃⁻. The rock in the chest of Leshan Giant Buddha is mainly composed of CaCO₃ and SiO_2. Therefore, the rock is prone to being corroded after being exposed to air and water. Rock weathering contributes more than 90% of the ions in the seepage water sample, and H₂CO₃ and H₂SO₄ jointly affect the weathering of sandstone in Buddha.

In order to reflect the whole process of stress-strain of rock subjected to freeze thawing in the cold region under external force, this paper uses the theory of statistical damage mechanics and assumes that the strength of rock microelements obeys Weibull distribution. Then, according to the maximum tensile strain failure criterion, a damage model of rock subjected to freeze thawing in the cold region is established by considering the coupling effect of freeze thawing and load. The theoretical solution of the model parameters is deduced, and the damage model is verified by the test results and damage constitutive model of the predecessors. The evolution law of the total damage curve of the rock under different freeze-thaw cycles is discussed, and the model parameters are analyzed. Finally, the influence of the freeze-thaw cycle on the stability of tunnel engineering is calculated by the numerical simulation method. The results show that the model established in this paper can well reproduce the stress-strain curve of the rock and reflect the post-peak strength of the rock. The total damage evolution curve of the rock under different freeze-thaw cycles is S-shaped, and it can be divided into three stages: initial damage stage, accelerated stage, and complete damage stage. Weibull distribution parameters m and $ {f}_{0} $ represent the brittle and plastic characteristics of rock, respectively. Additionally, with the increase in freeze-thaw cycles, the vertical displacement and the maximum principal stress of the tunnel surrounding rock increase. Meanwhile, the maximum principal stress of tunnel lining also increases. However, the stress of the tunnel surrounding rock increases slightly. After 10 freeze-thaw cycles, the settlement of surrounding rock at the top of the tunnel arch and the uplift of surrounding rock at the bottom increase by 17.87% and 19.24%, respectively; the maximum tensile stress and compressive stress extremes of the tunnel surrounding rock increase by 2.70% and 2.01%, respectively, while those of the tunnel lining increase by 21.52% and 17.87%, respectively.

To accurately predict the propagation of elastic waves in rails and explore the necessity of considering the bending-torsional coupling (BTC) of Timoshenko beam, a rail-fastener spatial infinite model considering the BTC of the beam was developed based on the spectral element method (SEM) and the symplectic method (SM). Based on model verification, the BTC effect of Timoshenko beam on the lateral natural frequency and velocity admittance of the rail was analyzed, and the effect of vertical preload dependence of fastener pads on the lateral bending vibration characteristics of the rail was analyzed theoretically and experimentally. The research results show that because of the BTC effect of the beam, the lateral bending resonance frequency (BRF) of the rail increases by about 29.6 Hz, and the bending and torsional pinned-pinned modes appear simultaneously in the lateral bending vibration of the rail. The vertical preload dependence of fastener pads mainly affects the lateral low- and mid-frequency vibrations of the rail. As the preload increases, the lateral BRF of the rail increases. When the preload is increased from 30 kN to 50 kN, the measured lateral BRF increases by about 13.7 Hz, while the increase is about 12.5 Hz and 21.7 Hz by considering the BTC effect of the beam or not. The variation law of lateral BRF of the rail considering the BTC of the beam under different preloads is closer to the measured results.

In order to describe the damage evolution process of layered rock mass more truly and accurately, a damage constitutive model for layered rock mass considering the residual strength was established, which adopted modified Lemaitre strain equivalence hypothesis, combining the elastic theory of transversely isotropic materials and the damage mechanics theory. The accuracy of the model was verified by the triaxial test data of shale, phyllite, and slate, and the whole process damage evolution law of rock mass with different bedding angles was analyzed. The research results showed that the model could describe the elastic deformation of layered rock mass, but also reflect the post-peak strain softening process well. In the initial loading process, the damage value of rock mass was near zero. With the increase of stress, the damage value showed slow growth, accelerated growth, and decelerated growth, until it reached the residual strength and then stabilized at one. When the bedding angle of the shale was 60°, the damage evolution curve was the steepest, the damage speed was the fastest, and it shale failed first. Because the phyllite was thinner in thickness and lower in strength, it failed first when the bedding angle was 90°. However, the slate was relatively thick and had higher strength, and it failed first when the bedding angle was 45°. The existence of a weak bedding surface of rock mass led to the anisotropy of mechanical properties and failure modes, and the damage evolution law showed remarkable differences.

In order to guide the shield tunneling control and crack prevention design of segmental lining during the construction of subway section tunnels, a numerical model of the fabricated lining structure of shield tunnels considering joints and segments was established. Based on the constitutive model of concrete smeared cracking, the cracking behavior of linear segmental lining under the adverse jacking force caused by axial tilt and end face lateral displacement of the jack was studied. The research results show that under the above two kinds of adverse jacking force, the segmental lining cracks caused by the jacking force can be divided into bolt hole cracks in the key block, longitudinal cracks in hand holes, and longitudinal cracks in the annular surface of the segment. The crack width is the largest at the ring-direction bolt hole in the key block when the jack axis is tilted axially, and the width of the three types of cracks exceeds the construction limit when the axial inclination angle reaches 3°. The width is the largest at the annular surface of the lining and the ring-direction bolt hole in the key block when the end face of the jack laterally shifts. Specifically, the overall downward lateral displacement of the end face is the most unfavorable situation. The cracking of segmental lining will increase steel reinforcement stress at the crack location, and the relationship between steel reinforcement stress and crack width is not affected by the change of inclination angle of the jacking force. Furthermore, the crack width is positively correlated with the steel reinforcement stress. During shield construction, the adverse jacking force of shield tunneling should be strictly controlled. In order to control the occurrence of cracks, it is suggested to strengthen the reinforcement in the position where cracks are easy to occur.

In order to study the durability of high-performance concrete (HPC) bridges in the marine environment, based on the rapid indoor freeze-thaw test of concrete, the durability of HPC under the coupled action of chloride salt erosion and freeze-thaw cycles was tested, and the mass loss rate and relative dynamic elastic modulus of concrete under different water-binder ratios, fly ash contents, and air contents were analyzed. According to the test analysis results, a quality prediction attenuation model of HPC under the coupled action of chloride salt erosion and freeze-thaw cycles was established. The results show that the water-binder ratio has a great influence on the salt-freezing resistance of HPC. The salt-freezing resistance of concrete decreases with the increase in the water-binder ratio, and it is suggested that the water-binder ratio should not be greater than 0.45; the addition of fly ash will reduce the salt-freezing resistance of concrete, and the salt-freezing resistance can hardly meet the requirements when the fly ash content is high. Therefore, the fly ash content should not be higher than 30%; as air content increases, the salt-freezing resistance of concrete first increases and then decreases. The air content of concrete considering the salt-freezing resistance requirements is recommended to be selected within the range of 4.5%–5.5%.

In order to investigate the heterogeneous traffic flow characteristics formed by the combination of connected autonomous vehicles (CAVs) and human-pilot vehicles (HPVs), as well as the impact of bus driving behavior on this environment, four following modes in heterogeneous traffic flow are initially analyzed: human-pilot car following, human-pilot bus following, adaptive cruise control (ACC) following, and cooperative adaptive cruise control (CACC) following. Subsequently, based on the characteristics of each following model, a cellular automaton model for vehicle following and lane-changing is constructed, which comprehensively considers the characteristics of CAV platoons, the response time characteristics of drivers and CAVs, and the cutting-in behavior of HPVs. By setting the following mode judgment parameters, different following mode characteristics are integrated to achieve a unified model representation. Lastly, through simulation experiments, the queuing intensity of CAVs at different penetration rates and the impact of bus lane-changing behavior on traffic flow are analyzed. The results indicate that promoting CAVs to form platoons at a certain penetration rate is more effective in improving road traffic efficiency than merely increasing the CAV penetration rate; a moderate amount of bus lane-changing contributes to the full utilization of road traffic capacity, while excessive bus lane-changing hinders normal traffic. The traffic efficiency attenuation caused by bus lane-changing decreases as the CAV penetration rate increases; under synchronized flow conditions, the execution rate of human-pilot cars is negatively correlated with road traffic efficiency; however, under congested flow conditions, the impact of human-pilot car execution rate on traffic efficiency is negligible.

When pedestrians move on the slope, their force condition, speed, and mental states are different from those on the flat road, so it is difficult to apply the existing social force model for effective simulation. Therefore, the social force model was improved by considering the movement characteristics of pedestrians on slopes. The improved model calibrated pedestrian speed on slopes based on previous empirical data to a desired value, and the probability calculation method of pedestrian falls under the pushing behavior was proposed. Meanwhile, pedestrian falls, injuries, and impatience were simulated according to their weight, acceleration, body pressure, and waiting time in real time. The simulation results of pedestrian counterflow on slopes show that the increase in slope gradient and initial pedestrian density prolongs the movement time and increases the per capita accident rate of the crowd to 38.0%. Pedestrian impatience contributes to the formation of lane effects but reduces the movement efficiency of the crowd. In the fundamental pedestrian flow diagram, the trend of the flow-density relationship under high slopes is not as obvious as that under a flat road, and the average speed of pedestrians under different slopes is relatively close.

To reduce the carbon emissions from logistics vehicles, this paper presented a two-echelon location routing problem (2E-LRP) model aiming at minimizing carbon emissions based on a carbon emission calculation method employing emission factors as the key parameter. The paper also designed a two-stage hybrid algorithm (TSHA) capable of rapidly solving a large-scale problem. The algorithm first simplified the 2E-LRP into the two-echelon facility location problem without taking vehicle routes into account and called Cplex to solve it to obtain the location solution of distribution centers and the assignment solution of customers. Based on the above solutions, the 2E-LRP was transformed into independent vehicle route problems, and then an improved ant colony algorithm was employed for a solution. All six largest-sized instances from the standard Prodhon benchmark were tested. The test results show that the TSHA-Ⅱ, with the same algorithm ideas as TSHA, can reduce the computation time to about 25 seconds with a decrease of 2.3% in solution quality. The TSHA is stable in solving 2E-LRP considering carbon emissions and can be used as an effective algorithm to solve the 2E-LRP considering carbon emissions.

To calculate passenger flow distribution in urban rail transits, a passenger flow assignment method based on inference of passenger spatiotemporal path is proposed with the data collected from the automatic fare collection (AFC) and train timetables. Firstly, the passenger travel time parameters are estimated with the above two types of data. The feasible path set of each origin–destination (OD) in the whole network is then obtained by using the feasible path search algorithm based on the node-inserting method. Subsequently, according to the inbound and outbound information from passenger smart cards, train timetable and matched feasible path set, an inference model of passenger effective travel path and train set is built to obtain the effective travel result set. Finally, a train operation is developed with the obtained effective result set, train load capacity, and train timetable to determine the sole effective travel path and riding train. A calculation system for the passenger flow in urban rail transit networks is designed and developed, and a case study is conducted on weekday passenger flow data of urban rail transit. The results show that the average difference of section passenger flow between the calculated results and operation reference data of upstream and downstream is 2.03% and 3.90%, respectively, and the trend of train load rate confirms to the line routing. Moreover, the source of transfer passenger flow at transfer station is stable in the morning and evening peaks, but the proportion of sources in the morning peak is more stable that in the evening peak.

Most of power allocation algorithms are based on ideal channel state information (CSI) to achieve performance optimization, which is not applicable in train-to-train (T2T) dual mobile terminal communication. For the hybrid network scenario of T2T and train-to-ground (T2G) in urban rail transit system, the CSI feedback delay is introduced to study the power allocation algorithm that can still guarantee the communication quality under non-ideal conditions. Given the situation that a single T2G user reuse a single T2T user pair, the optimization goal is to maximize the total transmission rate of T2G users, and a power allocation model is constructed under multiple constraints. First, according to a step-by-step concept, the non-convex model is divided into two sub-models of optimal allocated power calculation and optimal multiplexing users matching. Second, the optimal solution and the optimal value of the objective function in the feasible region are analyzed through linear programming, and the optimal distribution power is solved by the dichotomy. Finally, after screening the set of feasible multiplex pairs, the Hungarian algorithm is used for matching. Simulation results show that the proposed algorithm allows for the interruption probability constraint of T2T communication and the total transmission rate of T2G users in the urban rail transit system, and controls CSI feedback delay within 1.0 ms.

In order to solve the problem of misoperation of catenary and traction cables in a new continuous cable power supply system using the existing sectional protection scheme, firstly, the mechanism of load current on current longitudinal differential protection of the catenary was studied, and a fault component current longitudinal differential protection scheme of the catenary was proposed. Then the phasor method was used to analyze the influence of capacitance current on the existing protection scheme of traction cables under no load condition. The protection of longitudinal current difference was realized by shunting reactors at both ends of the traction cable in each sectional loop under no load and cutting off the reactor under load. The results show that the load current in the catenary supplied by the traction transformers on both sides is the cause of the misoperation of the current longitudinal differential protection of the catenary. However, the proposed short-circuit protection of the catenary composed of fault component current is not affected by the normal load current under the bilateral power supply. Under no load condition, the capacitance current will change the amplitude and phase angle of the end current of the traction cable compared with the first end current, resulting in the misoperation of the protection. The proposed method of shunting reactors at both ends of traction cables can solve this problem.

The bidirectional converter device can effectively inhibit the fluctuation of the DC-side grid voltage at traction substation, reduce the current transmitted between regions, and limit the rail potential. As the collaborative control strategy of the bidirectional converter and rectifier unit will directly affect the power flow of urban rail traction power supply system, a coordinated power supply scheme composed of a bidirectional converter device and a 24-pulse rectifier is proposed, and the comprehensive output characteristics of traction substation with this scheme are analyzed. The power supply calculation model of traction substation is established, allowing for the accurate active power loss of converter device, and a multi-state switching control strategy with hysteresis comparison is proposed to calculate the cooperative power flow for urban rail traction power supply system with a bidirectional converter device. Compared with Simulink simulation results, the effectiveness and accuracy of the algorithm are verified. In the simulation of a subway project, under the collaborative power supply scheme, when the traction network pressure increases, the maximum rail potential decreases by 12.6%–15.6% and 14.7%–17.5% up and down the whole line, respectively. The loss of DC traction power supply system and the overall cost of the system can be reduced by 9.7% and 1.17% at most. As the rectifier starting voltage of the bidirectional converter device increases, the rectifier/inverter power of some traction substations increases, and the loss of DC traction power supply system increases first and then decreases, but the rail potential changes little. In practice, when the inverter starting voltage of the bidirectional converter is fixed, increasing the rectifier starting voltage appropriately can achieve better energy saving.

In order to restrain the galloping amplitude of the positive feeder in the gale area of the Lanzhou‒Urumuqi high-speed railway and ensure the safe operation of the train, firstly, a novel type of low-wind-pressure catenary positive feeder was designed, and the aerodynamic parameters and galloping amplitude of the conventional catenary positive feeder and the low-wind-pressure catenary positive feeder under different wind loads were simulated and compared. Then, a three-dimensional finite element model of the low-wind-pressure catenary positive feeders with the three better anti-galloping effects was established and tensile loads were applied to simulate the stress condition of the positive feeder when the positive feeders were galloping. Finally, the deformation and variation stress of the low-wind-pressure catenary positive feeder were analyzed. The results show that, the deformation of the free end of the catenary positive feeder is much larger than that of the fixed end, the deformation of the aluminum strand layer is larger than that of the steel strand layer, and the further to the outer layer, the larger the strand deformation, twining alternately steel and aluminum layers can be considered in the feeder manufacturing to balance the electroconductibility and rigidity. The stress concentration occurs at the location where the strands squeezing with each other, and the stress concentration position is the same as the direction of the strand twining with each other. A buffer layer should be considered on the surface of the strands during the positive feeder manufacturing, to mitigate oscillatory shock between the strands when the positive feeder galloping, and to prolong the service life of the positive feeder. The larger the ratio of the groove radius of the low-wind-pressure catenary positive feeder to the radius of the conventional feeder, the greater the deformation of the outermost aluminum strands, the strands are more likely to break when the positive feeder is galloping. Therefore, the type selection of low wind pressure positive feeder should be comprehensively considered to balance the anti-galloping effectiveness and the service life.

In view of the corrosion detection of large thin-walled structural parts in industrial equipment, a corrosion detection method based on spectral coherence analysis using high-order Lamb waves was proposed. Firstly, the A1 mode Lamb wave with a frequency slightly higher than the cutoff frequency was adopted and transmitted at different positions on the corroded thin-walled structure, and the response signal of each propagation path was collected; then, the dispersion compensation technique was used to eliminate the dispersion effect in the signal, so the direct wave packet of A1 mode could be separated and extracted from the signal using a suitable window function. On this basis, the frequency spectrum difference coefficient (FSDC) of the extracted wave packet and the excitation signal was established as an index, which was subsequently discussed in terms of its sensitivity to corrosion defects of different widths and depths with the help of finite element simulation; finally, an experimental validation was conducted on a corroded aluminum plate, where the FSDC index of each path was combined with the probability imaging algorithm to locate and visualize the corrosion defect in the detection area. Results show that the FSDC value keeps zero for an intact path and stays between 0 and 1 for corrosions of different widths and depths. Compared with the traditional tomography method, the proposed method has better detection sensitivity and anti-interference ability.

In order to better perform the aerodynamic noise reduction design of high-speed trains, a 6-parametric model of the first bogie section of the high-speed train head car was established. The method designed by computational aeroacoustics and Latin hypercube sampling experiments was used, and the far-field aerodynamic noise, turbulent fluctuation power level, and acoustic power level inside the bogie cavity of 13 parametric models were obtained. The influence of underbody parameters on far-field and near-field aerodynamic noise was analyzed. The results show that the influence range of the underbody parameters on the far-field noise is 75.4–78.9 dB(A). The apron height, cowcatcher thickness, chamfer of the rear edge of the bogie cavity, and cavity length are negatively correlated with the far-field noise, while the chamfer of the leading edge of the cavity and the leading-edge included angle of the cowcatcher are positively correlated with the far-field noise. The changes in underbody parameters mainly affect the noise energy in the central frequency band of 315–1 250 Hz. The cowcatcher thickness and leading-edge included angle are negatively correlated with far-field noise, turbulent fluctuation power level, and acoustic power level inside the bogie cavity. The apron height is negatively correlated with the far-field noise and the turbulent fluctuation power level inside the bogie cavity and positively correlated with the acoustic power level inside the bogie cavity.

In recent years, the construction of intelligent monitoring equipment along railways and the environmental regeneration of new energy in the field of rail transit have attracted extensive attention. The basic principle of new energy regeneration technology is to capture clean environmental energy and convert the obtained energy into electricity to provide electricity for the normal operation of various intelligent sensors, traffic signal devices, and monitoring equipment. Many research achievements in various new energy regeneration technologies have been made in the field of rail transit worldwide, including wind, heat, solar, sound, brake, and vibration energy harvesting. Of these, vibration energy collection is a new energy regeneration technology with the highest degree of relevancy and the most in-depth research in the field of rail transit. The main forms of energy collection include electromagnetic, piezoelectric, friction, and hydraulic. By summarizing and sorting current research results, the existing technical problems and engineering application challenges can be summarized, including stability, durability, economy, energy size, motion amplification, and reliability. With the gradual maturity of such technology, the practical engineering applications of new energy regeneration technologies will promote intelligent and sustainable development in the field of rail transit.

In order to improve the visual representation and presentation of regional culture in the exterior design of urban rail vehicles, an optimization method of regional cultural factors for the exterior design of urban rail vehicles is proposed. Firstly, the influence evaluation system of regional cultural factors is constructed with variables including cultural shape factor, cultural color factor, and cultural connotation factor. Related data of the importance of regional cultural factors are obtained through the questionnaire survey. Then, the hierarchical structure evaluation model of regional cultural factors is constructed according to the analytic hierarchy process, and the influence weights of different regional cultural factors are analyzed. Finally, an exterior design scheme of the metro train with typical Chengdu regional cultural characteristics is proposed according to the findings. The research shows that historical relic and natural ecological shape factors should be given higher priority in the exterior design of vehicles; historical relic and natural ecological color factors should be emphasized in the exterior decoration design, and natural ecological and historical cultural factors should be highlighted in terms of cultural connotation.