As chips continuously enter and leave from the tool flute during the cutting process of the motorized spindle for magnetic suspension milling, the size and distribution of the system mass are constantly changing, leading to the nonlinear change of system dynamics characteristics. To address these issues, firstly, the mass of a single chip was calculated based on the principle of continuous metal cutting, and then combined with the theory of continuous beam vibration, the dynamics model of the “magnetic suspension bearing–motorized spindle–tool–chip” time-varying mass system was established by using the finite element method. Secondly, the Runge-Kutta method was used to solve the differential equation of motion of the system, and the influence of chip mass change on the natural frequency and mode shape of the system was analyzed during the entire process covering the chip’s entry into and leave from the tool flute. Then, the vibration response patterns of the system under the excitation of rotational inertial load, gyroscope torque, cutting force, and electromagnetic force of magnetic suspension bearings caused by time-varying chip mass were explored. Finally, the MATLAB software was used to simulate and solve the system. The results show that as the chip mass increases from 0 to 2.08 × 10⁻⁵ kg, the system’s first three critical speeds decrease by about 2.3, 0.7, and 0.3 r/min, respectively, indicating that the time-varying chip mass has a small effect on the system’s inherent characteristics. The rotational inertia load has a significant impact on the system’s dynamic response, especially at the cutting point, causing the radial vibration response and angular vibration response amplitudes at the cutting point to increase by 0–9.7 × 10⁻⁷ m and 0–2.5 × 10⁻⁵ rad, respectively, and it makes the radial vibration and angular vibration equilibrium positions at the cutting point to increase by about 5.1 × 10⁻⁷ m and 9.3 × 10⁻⁶ rad, respectively.

Compared with traditional wheel-rail transportation, maglev trains have some irreplaceable advantages such as high speed, low noise, smooth operation, and low maintenance cost, providing an ideal scheme for constructing a convenient urban transportation system. To realize precise speed control of maglev trains in complex disturbance environments, an active disturbance rejection control (ADRC) method with self-tuning parameters was proposed. Firstly, the longitudinal dynamic model of maglev trains was established by force analysis to describe the nonlinear hysteresis characteristics of maglev trains during operation. Secondly, the unknown parameters of the model and external disturbances were regarded as the extended state, and a third-order extended state observer was designed to observe the extended state in real time. In addition, the convergence condition of the observer was analyzed based on the Lyapunov stability theorem. Then, to solve the problem of many control parameters and difficult parameter adjustment in traditional ADRC, the multiple population genetic algorithm (MPGA) was introduced to realize adaptive optimization and adjustment of parameters. Finally, the simulation experiment was carried out based on the data collected from the real operation environment of maglev trains, and the simulation results show that compared with traditional ADRC, the speed control accuracy is increased by 22.7% and the tracking stability is improved by 25.6% by means of MPGA-ADRC method, which indicates that the proposed method can effectively improve the stability and ride comfort of maglev trains.

The intensifying global climate change is increasingly affecting the operational performance of existing transportation infrastructure due to extreme climatic events such as heavy precipitation, high temperatures, low temperatures, and drought, leading to severe damage. Meanwhile, with the further implementation of the strategy of building China with a strong transportation network, a significant number of new transportation infrastructure projects are being constructed in harsh environments, posing unprecedented challenges to the functionality, durability, and maintenance management of these new facilities. The characteristics of extreme climate loads include rapid and unpredictable variations, often accompanied by coupled effects of multiple disasters, rendering the mechanisms of damage to transportation infrastructure under their influence highly complex. To ensure the safety and effectiveness of transportation infrastructure under extreme climatic conditions, Chinese and international research on extreme climate and multi-disaster coupling was studied, and the research progress on spatiotemporal evolution of extreme climates and multi-disaster coupling effects was systematically reviewed. The impact mechanisms of multiple disasters on engineering structures were sorted out. Based on this foundation, the characteristics of extreme climate impacts were defined, and disaster prevention and reduction design principles for transportation infrastructure during the design, construction, and maintenance phases were proposed. Furthermore, methods for assessing multi-disaster risks to transportation infrastructure under extreme climatic conditions were comprehensively summarized, and future research was prospected, highlighting the importance of utilizing artificial intelligence and machine learning technologies for rapid prediction and assessment of extreme climatic disasters and analyzing changes in the performance of transportation infrastructure systems throughout their whole life cycle. This research provides valuable references for the disaster-resistant design, performance assessment, and resilience enhancement of transportation infrastructure such as bridges, roads, and tunnels under extreme climatic conditions.

The mechanical behavior of longitudinally connected ballastless track slabs in the transition section of subgrade and bridge is complex, and arching disease is frequent. The П-type end spine ballastless track in the transition section of subgrade and bridge was taken as the research object, and a track-bridge-end spine-subgrade integrated finite element model was established. The bilinear cohesive force model was introduced to simulate the bonding relationship between the slabs and the interlayers, and the longitudinal force distribution of the longitudinally connected track slabs in the transition section of subgrade and bridge under different temperature loads and end spine displacements was analyzed. The stress-sensitive area of the end spine, namely, the longitudinal stress characteristics of the track slabs at the junction of the transition section and the supporting layer and the relationship between the extrusion deformation of the junction and the arching deformation, were studied. The results show that the longitudinal compressive stress level of the track slabs at the main end spine and the junction of the transition plate and the supporting layer is the highest, and the maximum value under the extreme positive temperature gradient is 19.91 MPa. The friction plate and the bridge section are small, which corresponds to the limit capacity of each structure of the end spine. With the development of diseases such as deterioration and void of subgrade materials, the longitudinal resistance and interlayer friction decrease continuously, which leads to the increase in longitudinal deformation of the end spine, the decrease in longitudinal stress of the track slabs in the end spine area, and the increase in longitudinal stress of the supporting layer of the junction. When the longitudinal deformation reaches 6 mm, the longitudinal compressive stress of the supporting layer of the junction reaches 18.55 MPa, and the crushing risk of the structure is very high. The compressive arching of the junction greatly affects the bonding between the slabs and the layers of the track structure and increases the risk of arching disease. The research results can provide a reference for further optimizing and renovating the diseases of the transition section of the longitudinally connected ballastless track slabs and ensuring the safe and stable operation of high-speed railways.

To optimize the T-shaped retrofitting scheme of diagonal members, the influence of structural and material parameters on the bearing capacity of the members after retrofitting was investigated through theoretical analysis, experimental study, and finite element analysis. Firstly, a theoretical model of the T-shaped retrofitting section was established based on the composite beam theory, so as to analyze the improvement in flexural stiffness after T-shaped retrofitting. Secondly, eccentric compression static experiments of single-side connected angle steels for T-shaped retrofitting were conducted. Finally, the finite element model was used to analyze the effects of the slenderness ratio, width-to-thickness ratio, and material strength on the selection of the number of connectors. The results indicate that the improvement in flexural stiffness after T-shaped retrofitting decreases with increasing load. A decrease in the number of connectors leads to relative slip perpendicular to the direction of member deformation. For the experimental members, an increase in the number of connectors leads to greater bearing capacity, with a maximum retrofitting effect of 100.4%. For the T-shaped retrofitting scheme of diagonal members, two connectors are sufficient when the slenderness ratio is below 150. Otherwise, three connectors are required. The width-to-thickness ratio and material strength have no effect on the selection of connectors.

In order to achieve the safe application of red mud-based cementitious materials in road engineering, the mechanical properties and quality of red mud-based stabilized crushed stone base under freeze-thaw cycles were studied. The influence of freeze-thaw cycle temperature and number on mechanical properties and quality loss was explored by industrial CT scanning and SEM-EDS. Research has shown that when the temperature ranges from 20 ℃ to −20 ℃ for 28 days, the maximum quality loss rate of the cementitious material with a 5% dosage is 1.85%. The change in quality loss rate of stabilized crushed stone with 5% and 6% red mud-based cementitious materials is higher than that with 7% and 8% red mud-based cementitious materials. In addition, with the increase in freeze-thaw cycles, the quality loss rate continues to increase. Through industrial CT and SEM-EDS microscopic analysis, as the number of freeze-thaw cycles increases, the porosity of stabilized crushed stone increases. After the stabilized crushed stone undergoes 28 days of curing and 20 freeze-thaw cycles with a 6% dosage, the porosity increases by 1.53%, and internal crack damage increases and accumulates continuously, showing a changing pattern from less to more and from narrow to wide. The research results have a positive role in promoting the green construction of transportation engineering and the large-scale application of red mud.

Vertical stiffness is critically significant for the operational safety and ride comfort of high-speed electromagnetic suspension (EMS) trains on bridges, constituting one of the essential design parameters in bridge engineering. By using a three-span continuous girder as the study object, the vertical stiffness was modified by adjusting the cross-sectional moment of inertia. A coupled vibration analysis of the EMS train-bridge system was conducted under varying train speeds, rated suspension clearances, and temperatures. The variation rules of the dynamic coefficient of the bridge, acceleration of the train, and suspension clearance change with the adjustment coefficient of vertical stiffness of the bridge were discussed. The results show that when the adjustment coefficient of stiffness decreases to about 0.75, the dynamic coefficient of the bridge increases rapidly, and the vertical acceleration of the train is more sensitive to the vertical stiffness variation of the bridge than the suspension clearance change. When the cooling deformation is considered, higher train speed indicates greater vertical dynamic response of the bridge, and the track irregularity and rated suspension clearance have no obvious influence on the dynamic coefficient of the bridge. Higher train speed indicates smaller rated suspension clearance. When the effects of track irregularity and cooling deformation are considered, the adjustment coefficient of vertical stiffness of the bridge corresponding to the same vehicle dynamic response is larger.

In order to improve the seismic performance while maintaining the original style of the slab stone walls of Tibetan and Qiang residential buildings, the construction method of putting restraints on the slab stone walls of Tibetan and Qiang residential buildings by using a reinforcement skeleton system was proposed. Firstly, a typical wall of stone and wood structure in Lixian County was selected as the prototype, and a 1/2 scale ordinary slab stone wall W-1 and a wall W-2 with reinforcement skeleton system were designed. Secondly, comparative pseudo-static tests were carried out to study the failure forms, hysteretic properties, energy dissipation capacity, and deformation capacity of the two walls. Finally, the skeleton curves and hysteretic curves of the two walls were obtained by ABAQUS finite element numerical simulation and compared with the experimental results. The results show that the failure process of the wall under low cyclic load has an obvious stress stage, as well as crack initiation, expansion, and failure stages. Compared with those of the ordinary slab stone wall, the ultimate bearing capacity, energy dissipation performance, and failure displacement of the slab stone wall with reinforcement skeleton system are increased by 225%, 183%, and 67%, and the cracking and damage degree of the wall are significantly reduced. The trend of skeleton curves obtained by numerical simulation and experiment is similar, with a S-shaped pattern. The shapes of hysteretic curves are different, but the hysteretic ring area of W-2 is larger than that of wall W-1. The ultimate loads of W-1 and W-2 obtained by numerical simulation are 21.62 KN and 78.04 KN, respectively, with a relative error of less than 20% compared with the ultimate load measured by the experiment

In order to identify the nonlinear aerodynamic forces and calculate nonlinear flutters of a nonlinear dynamic system, an autoencoder model based on the neural network method and numerical solution of motion equation was proposed. The 5∶1 rectangular cross-section was taken as the research object. Through free vibration wind tunnel tests of the sectional model, the amplitude dependence of the nonlinear damping and the steady-state amplitude responses of the nonlinear flutter of the system were tested, and it was clarified that the tested cross-section had the only steady-state flutter response at different reduced wind speeds. Based on the experimental data, the proposed autoencoder model was trained. The nonlinear aerodynamic force encoder model that accurately described displacement and speed was obtained to realize motion time-history analysis of the nonlinear flutter of the 5∶1 rectangular cross-section under different dynamic parameters. Research results show that the proposed autoencoder model can accurately identify the nonlinear aerodynamic force time-history containing high-order harmonic components only by relying on a free vibration wind tunnel test without the need to carry out force or pressure tests; the proposed model can accurately reproduce the motion time-history of nonlinear flutter under different initial conditions and the steady-state amplitude responses at different reduced wind speeds. The maximum error of torsional steady-state amplitude is less than 5%, and the average error is 1.15%. It has high extensibility and can provide a reference for subsequent related research.

The existing detection methods for the insulation of cable terminals of electric multiple units (EMUs) are complex and susceptible to onsite noise interference, and they thus have low detection efficiency. Therefore, a novel method for detecting the insulation condition of cable terminals based on electric field intensity was proposed. Firstly, cable terminals of EMUs with prefabricated air gap defects of different lengths were prepared. Secondly, high frequency current transform (HFCT) signals of the prefabricated air gap defects in the cable terminal samples were obtained. Finally, electric field intensity values of cable terminals with different defect lengths were measured by using electric field sensors. The research results show that by analyzing the peak value of HFCT signals and the electric field intensity characteristics of cable terminals with defects, the development of defects in cable terminals can be divided into three stages: S₁, S₂, and S₃. As the defect size increases, the interquartile range, mean value, variance, and coefficient of variation of the electric field intensity along the surface of the cable terminals increase. When the interface defect increases from 20%l to 100%l (l refers to the length of the stress control tube in the first layer inside the high-voltage cable terminal), the slope of the interquartile range of electric field intensity increases from 0.126 to 0.671, and the variance of electric field intensity increases by approximately 81.3% for the pre-exponential factor and 80.66% for the absolute value of the offset.

To address the issue of settlement and cracking of adjacent roads during the excavation of urban foundation pits, the research object was extended from a one-dimensional structure to a two-dimensional structure based on the Winkler theory. Firstly, a calculation model for the settlement field caused by foundation pit excavation was established, and the control equation for road flexural deformation was derived. Secondly, a two-stage analysis method was adopted by considering factors of foundation pit excavation depth, aspect ratio, support stiffness, and thickness of soft soil layer above the pit bottom, so as to provide a correction formula for settlement field caused by foundation pit excavation and a method for predicting maximum surface settlement. Thirdly, the settlement field was substituted into the control equation for road flexural deformation, and a fourth-order nonlinear partial differential equation was solved by using the finite difference method. Finally, the above road calculation and analysis model under the condition of foundation pit excavation was verified by an engineering example. By comparing the field monitoring data with the theoretical solution and numerical simulation, it was found that the errors in road settlement were 15% and 8.3%, respectively, both of which are within acceptable limits, thereby confirming the reliability of the road calculation and analysis model proposed in this study under the condition of foundation pit excavation.

To accurately assess the overall safety of transmission towers with asymmetrical legs, a refined numerical model for a transmission tower with asymmetrical legs was established based on a 500 kV transmission line project. Based on the Technical Specification for the Design of Steel Supporting Structures of Overhead Transmission Line (DL/T 5486—2020) and numerical results, functional expressions for different failure modes of the transmission tower with asymmetrical legs were derived, and these were equivalently described using the principle of equivalent extreme value events. Subsequently, random sample points were generated based on the low discrepancy sequence method, and the sample responses were calculated to obtain statistical moments of the equivalent functional expressions. Finally, the overall reliability index of the transmission tower with asymmetrical legs was calculated using the improved maximum entropy method. The results show that the relative error and computational cost of the overall reliability index of the transmission tower with asymmetrical legs obtained by this method are 0.46% and 0.05%, respectively, compared with the Monte Carlo simulation (MCS) method. The reliability index derived from a single failure mode is lower than the overall reliability index of the transmission tower with asymmetrical legs, suggesting that the latter is more accurate for the safety assessment of transmission towers with asymmetrical legs. Moreover, there is an inverse relationship between the difference in tower leg lengths and the overall reliability index of the transmission tower with asymmetrical legs. Specifically, the overall reliability index of a transmission tower with a 16-meter leg length difference is 15.72% lower than that of a transmission tower with equal-length legs. Therefore, it is recommended to avoid excessive leg length differences during the design phase.

A total of 16 concrete-filled high-strength steel tube specimens were designed to evaluate the effects of shear-to-span ratio and concrete strength on the shear behavior of concrete-filled high-strength steel tube specimens. The failure mode and shear-displacement curve of the specimens were obtained through the test, and the effects of shear-to-span ratio, core concrete strength, and other parameters on the failure mode, shear-displacement curve, shear-shear strain curve, shear strength, and shear stiffness were compared. The results show that similar to conventional concrete-filled steel tube specimens, the shear-to-span ratio is the key parameter controlling the failure mode of the concrete-filled high-strength steel tube specimens. When the shear-to-span ratio is 0.2 or 0.5, shear failure occurs; when the shear-to-span ratio is 0.8 or 1.0, shear-flexural failure occurs. By implementing ultra-high performance concrete (UHPC), the deformation capacity of the concrete-filled high-strength steel tube specimens (with a shear-to-span ratio of 1.0) is reduced by 61.4%. However, shear strength and stiffness increase by 38.9% and 85.7%, respectively. Additionally, local buckling of the steel tubes is effectively delayed, and the damage degree of the specimens is reduced. The inclination angle of the main diagonal cracks in the core concrete decreases with an increase in the shear-to-span ratio but is not affected by the concrete strength. The average value of tested shear strength/calculated shear strength (V_exp/V_u) is 0.97, with a deviation of 0.03, showing higher accuracy and smaller dispersion. It is considered that the formula can accurately predict the shear strength of concrete-filled high-strength steel tubes.

To achieve high-quality coordinated development of roadbed and environment in mountainous railways, a coupling optimization and regulation method of roadbed and environment was proposed. Firstly, the compatibility and symbiosis between the railway roadbed and the environment were defined, and a green element indicator system was constructed. The coupling regulation framework was clarified by combining the coupled Rubik’s cube game model. Secondly, the coupling coordination degree model, pressure bearing model, and functional relationships between key elements were used to jointly construct the objective function and constraint conditions for roadbed and environment regulation and optimization. The green key elements of roadbed engineering were taken as the main control variables, and an intelligent optimization algorithm, namely the chameleon swarm algorithm (CSA) was adopted to solve them, obtaining the optimal solutions of each main control variable in a compatible and symbiotic state. Finally, an empirical analysis was conducted by using the railway roadbed in a certain mountainous area as an example. The results show that when the main control variables of road cut excavation size, embankment filling size, support structure design, support structure layout, engineering protection structure design, slope engineering protection layout, plant protection structure design, slope plant protection layout, ecological sound barrier structure design, and ecological sound barrier layout are optimized by 36.83%, 43.14%, 49.93%, 68.91%, 69.98%, 68.91%, 23.42%, 68.91%, 19.64%, and 19.60%, respectively, the evolution of railway roadbed and environment from primary coordination state to intermediate coordination state can be achieved. The research results verify the rationality of the constructed roadbed and environment regulation and optimization model and the effectiveness of CSA in finding the optimal solution, providing a scientific basis for achieving green construction of railway roadbed engineering in mountainous areas.

To study the heat–mass transfer patterns and structural damage mechanisms of sulfate saline soil under freeze–thaw cycles, a freeze–thaw cycle test was carried out under non-pressurized supply condition with saline soil from Hexi Corridor as the research object. The pore structure damage mechanism of sulfate saline soil before and after freeze–thaw cycles was analyzed using nuclear magnetic resonance (NMR) and scanning electron microscope (SEM). The study shows that temperature transfer in the sulfate saline soil under freeze–thaw cycles exhibits the “depth effect” and “time-lag effect,” with a time lag of about five hours. The freezing depth initially develops downward before stabilizing, reaching a maximum depth of 8.54 cm. The solution supply amount increases as temperature decreases and decreases as temperature rises. Water and salt content increase in the frozen zone after a 240-hour freeze–thaw cycle while remaining basically unchanged in the unfrozen zone. The deformation of saline soil due to salt-frost heave follows a cyclic pattern of “heave and thaw,” with a time lag in response to temperature changes. Repeated cycles of “freezing–condensation–crystallization–thawing–dissolving” cause significant increases in medium and large pores of saline soil, leading to interconnected cracks. The soil structure transitions from a laminar structure before freeze–thaw cycle to a flocculent structure afterwards.

To reduce insufficient displacement in the contact area between the movable point frog’s point rail and wing rail, minimize transition force at the transition points of point rail, and improve the frog’s longitudinal smoothness, an optimization method for the design parameters and key components of movable point frogs was proposed. The minimum flangeway width of the No.18 movable point frog was selected as the optimization target. Based on the existing structural parameters and finite element method, a model for point rail transition calculation was established, and the method of successive approximation was used to optimize the design method of the transition displacement curve of the point rail. Under the different frog form and position tolerances for both straight/diverging lines, an optimized design was proposed with a second traction point stroke of 50.7 mm, along with the structural design scheme for key components of the frog in the straight-through state. The results show that the maximum deviation between calculated and designed point rail transition displacements is 6.64 mm, occurring at the elastic bending center. The computed minimum flangeway width (90.7 mm) closely matches the measured average value (90.9 mm), ensuring safe vehicle passage. Additionally, the second traction point stroke is reduced by 8.33 mm compared to existing frog designs, lowering the required transition force at the second traction point.

In the application scenarios of unbalanced samples such as airborne lithium-ion battery failure identification, the support vector machine (SVM) algorithm has the problem of hyperplane offset separation. To address this issue, the segmented penalty parameter support vector machine (SPP-SVM) algorithm was proposed. The SPP-SVM divided all samples into different segments during the training process and automatically adjusted the penalty parameters of each sample based on the identification errors within each segment, thereby achieving hyperplane offset suppression. The features were extracted and screened based on capacity increment analysis and grey correlation analysis methods, and then, the lithium-ion battery failure identification model was established based on the SPP-SVM algorithm. By utilizing the NASA lithium-ion battery dataset and the University of California Irvine (UCI) datasets as experimental subjects, comparative experiments were conducted. The results show that the SPP-SVM algorithm has better identification performance than SVM combined with optimization algorithms. On the lithium-ion battery dataset with a large degree of imbalance, the F1 score is improved by 11.7%. The SPP-SVM algorithm reduces the training time on the lithium-ion battery dataset and UCI dataset, offering a tenfold improvement. These results demonstrate that the SPP-SVM algorithm can effectively suppress hyperplane separation offset and improve identification performance in cases of sample imbalance.

Efficient geographic and geological knowledge services for railway engineering form a crucial foundation for supporting the multi-scale and multi-disciplinary intelligent applications of digital twin technology in railways. To improve the completeness of query results and enhance the capability for integrated analysis across the multi-scale “region–engineering project–construction site” applications of railway digital twins, a meta-network model for the dynamic distribution of geographic and geological knowledge was proposed. This model was designed as a distributed knowledge base network system, with railway agents, business departments, knowledge relationships, and multi-scale application scenarios as key nodes. A meta-network disruption algorithm for distribution optimization was implemented, with node importance assessed using degree centrality indicators. By analyzing the distribution influence through network perturbation, the influence range of nodes was calculated, obtaining the optimized distribution structure of the knowledge base. To validate this approach, it was applied to optimize the distribution of the knowledge base within the knowledge base management and application scenario for railway digital twins of a major railway bridge project. Experimental results show that, when processing knowledge retrieval tasks at the engineering and regional scales, the distribution optimization method increases the number of query results with reduced retrieval time and enhanced result matching accuracy.

The design speed of the superconducting maglev train reaches 600 km/h, causing intensified flow around the vehicle body and a sharp rise in aerodynamic loads. To study the train’s levitation state under aerodynamic loads, the finite element method was used, and the SST k-ω turbulence model was adopted to calculate the aerodynamic characteristics of a certain type of maglev train under open wire conditions. Additionally, based on these aerodynamic characteristics, a method for extracting aerodynamic loads and loading them in parts was proposed, which could more accurately reflect the dynamic responses under aerodynamic loads. The aerodynamic characteristics of the maglev train indicate that the U-shaped track significantly restricts flow near the vehicle body, making the tail vortex dissipate over a considerable distance within the U-shaped rail. Variations in transverse clearance between the maglev suspension frames and the track lead to the formation of negative pressure beneath the suspension frames. By taking a speed of 600 km/h as an example, the overall extraction of the head train and the middle train generates lift force, while the tail train experiences downforce. Additionally, the lift force is extracted from the individual components of the three vehicle bodies, and the lift amplitude in descending order is the head train > tail train > middle train. The suspension frames experience downforce, with the pressure amplitude of the first and fourth suspension frames being greater than that of the second and third suspension frames. Although the aerodynamic load force remains consistent across the two extraction methods, the aerodynamic lift amplitude of the vehicle body extracted through partial components is approximately five times greater than that of the whole extraction method. The results of vehicle dynamics under aerodynamic load reveal that the impact of aerodynamic load on suspension frame displacement is minimal, with the maximum height variation being less than 7 mm and showing little difference between the various loading methods. The primary distinction between the two loading modes in terms of dynamics is observed in the variation of the air spring force, where the maximum air spring force in the partial component loading mode is 2.86 times greater than that in the whole loading mode.

To evaluate the design rationality and operation reliability of the magnetically suspended fluid machinery, the API617 standard was applied to analyze its vibration and stability. Firstly, the relevant specifications and requirements for magnetically suspended fluid machinery in the API617 standard were introduced. Then, a magnetically suspended blower was taken as the research object, and rotor dynamics analysis, closed-loop transfer function testing, vibration analysis, stability evaluation, and other work were carried out based on the API617 standard. The results indicate that all indicators meet the API617 standard requirements. The separation margins between the rotor operating speed and critical speed are 69.7% and 53.8%, respectively, and the design is reasonable. The modelling of the magnetically suspended rotor system is accurate and can be used to predict the dynamic behavior of the rotor; the peak sensitivity transfer function values of the radial active magnetic bearing (AMB) system are all in zone A, while those of the axial AMB are in zone B, meeting the requirements for long-term and stable operation. The rotor vibration within the operating speed range is less than 10 μm, far below the vibration limit requirement.

To optimize the deterioration assessment and maintenance of ballasted tracks, it is of great value to study the breakage process and mechanism of ballast particles. Through a uniaxial breakage test on the single ballast particle, the equivalent stress required for its failure was determined. The deformation behavior under load was analyzed based on the ballast particle breakage process and loading force. Laser grating scanning of the ballast particle geometry was performed, and a minimum bounding rectangle method was used for specification. Rigid blocks were used for ballast particle packing, and a comparison was made with the traditional spherical particle packing method. The breakage process of ballast particles constructed with rigid blocks and the initiation of microcracks within the ballast particles were analyzed. In addition, the discrete element contact parameters for ballast particles with different geometries were studied, and a neural network model optimized by a genetic algorithm, namely GA-BP was used to predict the bond strength for ballast particles with different equivalent particle sizes. The results show that in the discrete element model, the bond strength of the ballast particles increases with the increase in its equivalent particle sizes. Specifically, for equivalent particle sizes in the ranges of [25, 39), [39, 48), [48, 56), [56, 64), and [64, 80) mm, the corresponding average bond strengths are 151.85, 159.45, 166.71, 175.29, and 185.29 MPa, respectively.

The soil–phyllite mixtures are widely distributed in the northwest of Sichuan, and excavation of slopes in these areas under rainfall conditions can cause large-scale instability, posing threats to the safety of transportation engineering construction and operation. The permeability characteristics of soil–rock mixtures significantly affect the stability of excavated slopes, and the spatial orientation of flat phyllite is the key factor affecting the permeability of soil–phyllite mixtures. Based on the spatial orientation characteristics of phyllite, a self-developed large-scale permeameter was used to examine permeability characteristics of soil–phyllite mixtures under different conditions, including various rock content and particle sizes, and the influence of these factors on the permeability of such mixtures was studied. The results show that when the rock content increases from 0% to 35%, the permeability coefficient of the mixture decreases by 49.28%, while the critical and failure hydraulic gradients increase by 159.38% and 54.17%, respectively, making piping failure less likely to occur. When the rock size increases from 20–40 mm to 60–80 mm, the permeability coefficient increases by 34.62%, and the critical and failure hydraulic gradients decrease by 23.15% and 10.3%, respectively, making piping failure more likely to occur. These findings provide references for evaluating the hydraulic characteristics of soil–phyllite mixtures and assessing the excavated slope stability in northwest Sichuan.

To investigate the effect of high temperature on the deterioration of the physical and mechanical properties of sandstone, uniaxial compression tests were conducted on thermally-treated sandstone subjected to different temperatures. Firstly, the deterioration characteristics of macroscopic mechanical parameters of sandstone were obtained through the analysis of mechanical strength and failure modes. Secondly, the influence of different temperatures on the energy evolution mechanism and elastic energy dissipation ratio of sandstone was studied. Finally, combined with the temperature and load damage factor, the piecewise function method was applied to develop a thermo-mechanical coupling damage constitutive model, considering the crack closure stage. The results show that as temperature increases, the peak strength and elastic modulus of thermally-treated sandstone increase first and then decrease, reaching a maximum value at 200 ℃. The failure mode transforms from oblique shear to “Y”-shaped conjugate tension–shear mixed failure, with the critical temperature threshold for the brittle and ductile transition occurring at 400 ℃. Based on dissipated energy evolution characteristics, the deformation and failure process is primarily divided into crack closure, elastic, macro-crack extension, and post-peak stages. The turning point of the elastic energy dissipation ratio (K) serves as the critical point where sandstone transitions from elastic to plastic behavior. The model’s size parameter (m) first increases and then decreases with increasing temperature, while the shape parameter (n) gradually decreases, reflecting the strength and plasticity of sandstone. The good agreement between the theoretical model and the laboratory results indicates that the model can invert the whole process of damage development of sandstone under thermo-mechanical coupling conditions.

The hydro-pneumatic suspension has the functions of cushioning and damping, body attitude adjustment, etc., but its structure is complex, with large pressure impact and high wear resistance and sealing. The excellent suspension cylinder structure, hydro-pneumatic suspension system, and control method are the important conditions to determine the driving performance of the vehicle. Firstly, the type of hydro-pneumatic suspension was analyzed, and the classification and principle of hydro-pneumatic suspension were summarized from the aspects of suspension structure, working characteristics, and control mode. Secondly, from the perspective of suspension controllability, the hydro-pneumatic suspension technology was discussed in terms of structural design and optimization of hydro-pneumatic suspension, mathematical modelling, and control algorithm and strategy. By analyzing the characteristics and shortcomings of existing structures, it is concluded that passive suspension is simple in structure and mature in technology, but it lacks adaptability. The semi-active suspension has low energy consumption, low cost, fast response, and high reliability, but its adaptability is limited. Active suspension has excellent performance, but it has high energy consumption, high cost, and complex system structure and control strategy. Finally, the development status and research direction of the three types of suspension were summarized and prospected, so as to provide a reference for the further research and development of vehicle hydro-pneumatic suspension design and control methods.

To study the mechanical constitutive model of steel bridge coating, uniaxial tensile tests were carried out on the long-lasting coating system, obtaining the stress–strain curves for the topcoat, intermediate coat, primer, and composite coating. The unified expression for the constitutive equation of the ascending segment of the long-lasting coating system was obtained through dimensionless processing, with corresponding constitutive equations provided for each coating film. The results are as follows. 1) The stress–strain curve for H06-X epoxy zinc-rich primer (80% zinc content) and long-lasting composite coating consists of an elastic and plastic stage, a strain-hardening stage, and a failure stage; the stress–strain curve for H06-C2 epoxy thick mica ferric oxide intermediate coat consists of a strain-hardening stage and a failure stage; the stress–strain curve for E01-JY fluorocarbon topcoat consists of an approximate linear elastic stage and a failure stage. 2) Based on the stress–strain curves, the mechanical property parameters of the primer, intermediate coat, topcoat, and composite coating, such as the elastic modulus, Poisson’s ratio, shear modulus, uniaxial tensile strength, and tensile fracture strain, are obtained. The primer shows the highest uniaxial tensile strength, followed by the intermediate paint, with the topcoat being the weakest. In contrast, the topcoat exhibits the best deformability, followed by the intermediate coat, with the primer showing the worst.

In order to explore the variation of the vulnerability of the en-route network caused by cascading failure, the vulnerability of the en-route network was analyzed based on the cascading failure process of different attack methods. By combining with the actual overcapacity operation of the en-route network, the overload operation of the nodes in the non-failure state, the probability of node failure, and the divertability of the load passed by the nodes were extracted. The cascading failure model of the en-route network and the cascading failure process based on different attack methods were constructed, and the en-route network-level vulnerability index was proposed from the perspective of the loss of waypoint operation capacity, as well as the vulnerability analysis method combined with the cascading failure model. The correlation between the vulnerability of the en-route network and the proposed model parameters was analyzed by studying the operation data in Eastern China, and the change rule of the vulnerability index of the en-route network under different parameters was explored. Three kinds of attack experiments were designed, and the results show that the operation capacity of each waypoint increases with the overcapacity range of the load flow, and the vulnerability of the en-route network decreases; the en-route network is more sensitive to selective attack methods, especially those based on the betweenness.

Wheel-rail profile compatibility has an important influence on the dynamic performance of rail vehicles. The present standard JM3 wheel profile has a large difference in equivalent conicity when it is matched with different types of rail profiles in China. It has the problem of locomotive swaying caused by too low equivalent conicity when the profile is matched with the grinding rail with large rail cant. To address these issues, the optimization objective of reducing the equivalent conicity dispersion of the wheel profile matched with CN60 and CN60N rail profiles under different rail cants was set. The wheel profile was described by a method combining arcs and straight lines. The JM3 wheel profile was optimized by utilizing NSGA-II genetic algorithm to improve the lateral position parameters of the two arc centers near the rolling circle. The wheel-rail contact characteristics and the locomotive dynamic simulation of the wheel profile before and after optimization were compared. The results show that when the optimized wheel profile is matched with the rails above, the nominal equivalent conicities at the 3 mm transverse displacement of the wheelset are all about 0.1, which reduces the equivalent conicity dispersion of the original JM3 wheel profile and improves the adaptability of the wheel profile to different rail profiles and line conditions. At the same time, the locomotive hunting stability, lateral stability, curving performance, and wear performance index of the optimized profile are all improved compared with the original wheel profile. In addition, the phenomenon of low-frequency swaying of locomotives on specific lines is eliminated.

In order to implement continuous descent operation (CDO) in a congested terminal control area and estimate its CO2 emission reduction benefits, a 4D trajectory prediction method for CDO based on data drive and optimal control theory was proposed. Firstly, the affinity propagation trajectory clustering method was employed to recognize typical horizontal arrival routes. According to typical horizontal arrival routes, a multi-phase optimal control model for CDO in vertical profiles was established, with the objectives of minimizing time and fuel consumption. Additionally, a novel solving method, namely genetic algorithm-based CDO (GACDO) for optimal control model was proposed. Finally, 4D trajectory prediction and emission reduction benefit comparison experiments in typical horizontal arrival route identification and CDO modes were conducted by using actual trajectory data in the terminal control area. The experimental results show that ideal 4D trajectories for CDO can be achieved. With the minimum time as the optimization objective, the average operation time and CO2 emission are reduced by 26% and 8%, respectively. With the minimum fuel consumption as the optimization objective, the operation time and CO2 emission are decreased by 17% and 20%, respectively.

Land use type in China is complex, and it is difficult to accurately identify urban land use type by relying on a single remote sensing image or point of interest (POI) data. To address this issue, a fine identification method combining remote sensing images and POI data was proposed. Firstly, to finely identify urban land parcel functions, a 500-meter grid was selected as the research unit; secondly, POI data were extracted, and kernel density distribution maps of various land uses were generated. Data preprocessing, data segmentation, and data enhancement were performed on remote sensing and POI image data to extract effective information. Finally, the POI kernel density distribution map and high-resolution remote sensing image data were fused together, and the current land use data was used as the label to construct the UNet++ network to classify urban land parcels. The model parameters were optimized using the cosine annealing (CA) algorithm, and the proposed method was tested in Shenzhen City. Migration verification was carried out in Luohu District and Nanshan District. The results show that the average accuracy of the urban land use identification model fused with POI data is 70.6%, which is 6.7% higher than that of the identification model using only remote sensing data; after using the CA algorithm, the model accuracy is increased by 1.5%. The migration verification of the model is carried out, and the average accuracy of the model is 72.6%. This shows that the model is robust. In addition, POI data makes up for the shortcomings of remote sensing images that only involve spectrum, texture, and physical attributes of ground structures, and it can better identify commercial land and public management and service land. The accuracy is 7.5% and 6% higher than that of a single data identification model.

The wheel-rail interaction force is the key index to evaluate the operation quality of rail vehicles. An identification method based on the square root cubature Kalman filter (SRCKF) algorithm was proposed for online monitoring of the wheel-rail vertical force of rail vehicles. By taking the vehicle-track vertical coupled dynamics model considering the nonlinearity of suspension elements as an example, a nonlinear process function of wheel-rail vertical forces and state variables of vehicle components was established. The vertical accelerations of the vehicle body, frame, and wheelset were adopted as observations, and the SRCKF algorithm was employed for the recursive estimation of wheel-rail vertical forces. Furthermore, a vehicle dynamics model and its corresponding wheel-rail vertical force estimation model of 17 degrees of freedom were established to identify the vehicle’s left and right wheel-rail vertical forces under actual irregularity excitation. Simulation results indicate that the proposed method can precisely identify wheel-rail vertical forces of vehicles excited by the random irregularity, rail corrugation irregularity, and rail weld irregularity, with the identified value of wheel-rail vertical forces is in good agreement with the simulation value in both time domain and frequency domain. The correlation coefficients are 0.988, 0.999, and 0.969, respectively. When the proposed method is used to identify the vehicle’s wheel-rail vertical force, the lowest correlation coefficients of the left and right wheel-rail vertical forces are 0.747 and 0.720, respectively, and the correlation coefficient of the sum of the left and right wheel-rail vertical forces is 0.999.

To address the limitations of using an advance guide tunnel for controlling large deformations of surrounding rock in soft rock tunnels, a deformation control method of “advance stress release + circumferential (lagging) grouting + lengthened anchor rod” was proposed after a thorough analysis of the large deformation characteristics of soft rocks and associated problems. Based on a unified model for the degradation of post-peak stiffness and strength of soft rocks and a unified strength criterion, the elastic-plastic solutions for the advance guide tunnel and main tunnel surrounding rock were obtained. Then, the constitutive model for the degradation of post-peak stiffness and strength of soft rocks was developed in FLAC3D finite difference software, and the deformation and stress distribution of the advance guide tunnel and main tunnel surrounding rock were obtained. Finally, the influencing factors such as softening modulus, grouting parameters, radius of advance guide tunnel, and distance between two tunnel faces were analyzed. The research results indicate that the advance guide tunnel can effectively release the surrounding rock deformations induced by compression, and the loosening and fracturing of the rock mass are the main reasons for excessive deformations and stability decrease of the release layer and main tunnel surrounding rock. Circumferential (lagging) grouting can effectively control the loosening deformations of the surrounding rock during excavation, improve the stress distribution of the surrounding rock, and enhance the load-bearing capacity of the surrounding rock. Larger values of the softening moduli M_c, M_φ, and M_E indicate strong surrounding rock deformations of the advance guide tunnel. Larger values of grouting parameters c_g, φ_g, and E_g indicate deformations of the main tunnel surrounding rock. Increasing the excavation radius r₀ of the advance guide tunnel and increasing the distance between the two tunnel faces (advance guide tunnel and main tunnel) can make the initial ground stress release more sufficient.

In the wide speed range of sensorless control, the traditional super-twisting second-order sliding mode observer algorithm had a problem that the error of rotor position estimation would change with the speed in the permanent magnet synchronous motor (PMSM). In order to improve the control performance of the motor speed and reduce the error of rotor position estimation, an improved sliding mode observer based on hyperbolic function was proposed, and an online identification scheme of stator resistance was designed. A disturbance voltage observer was designed to estimate the distortion voltage caused by the nonlinearity of the inverter on line. Finally, the hardware-in-the-loop test was carried out to verify the feasibility of the scheme. The test results show that the error of position estimation can be reduced by 7.6%, and the accuracy of velocity estimation can be increased by 5.8%.

Transformer insulation level and health state are crucial to the safety and stability of the power grid. In order to study the practical engineering problem that the audible acoustic signals collected outside the box may be mixed with other interference signals, such as corona sound and bird song when there is a discharge fault inside the 750 kV transformer, a voiceprint recognition of 750 kV transformer and pin-plate discharge aliasing signals based on sparse representation theory (SBSS) and convolutional neural network (CNN) was proposed. Firstly, the normal operation sound signal of Wusheng 750 kV Substation was collected as the background sound, and the discharge sound signal and the common interference sound in the field were used as the foreground sound by constructing the pin-plate discharge model. The aliasing sound signal was constructed by adding the foreground sound with different signal-to-noise ratios to the background sound. Secondly, the blind separation algorithm based on SBSS was used to realize the separation of target foreground and redundant background voiceprint spectra. Finally, the hyperparameters of the CNN model were optimized to improve the classification performance of the model on the separated various types of foreground voiceprint spectra. The results show that the blind source separation algorithm can eliminate the redundant background sound interference so that the neural network can focus on the classification and recognition of foreground sound. The proposed method can separate foreground voiceprint in the aliasing sound signals, and the recognition accuracies of the CNN, the support vector machine (SVM), and the back-propagation neural network (BPNN) after separation are improved by 7.6%, 17.2%, and 14.3%, respectively.

In order to study the variation law of water film thickness of multi-lane drainage asphalt pavement under ultimate rainfall intensity, a full-scale experimental section of multi-lane drainage asphalt pavement was constructed in the laboratory based on the seepage characteristics of drainage asphalt pavement. The water film thickness of the road surface was measured under different rainfall intensities, and the variation law of water film thickness with factors such as rainfall intensity and drainage path length of the pavement was analyzed. A model for predicting the water film thickness of drainage asphalt pavement under heavy rainfall was proposed, and on-site verification of the prediction model was conducted on the Nanning Ring Expressway in Guangxi Province. The ultimate rainfall intensity for drainage asphalt pavement without water film was determined based on a water film thickness prediction model. The research results indicate that the measured water film thickness of the drainage asphalt pavement increases with the drainage path length of the pavement and rapidly increases with the increase in rainfall intensity. During moderate to light rain periods with minimal rainfall, no water film will appear within 3 m of the road center; the water film thickness increases with the increase in rainfall and drainage path length, and it decreases with the increase in pavement thickness, slope, and porosity; when the drainage path length does not exceed 2 m, drainage asphalt pavement can withstand extremely heavy rainstorm without water film. When the drainage path length exceeds 10 m, the rainfall intensity reaches the level of heavy rain, which will form a water film on the road surface.

In order to study the seismic fragility of subway stations situated in loess sites, a typical two-story three-span subway station structure in a loess area was chosen as a representative example, and incremental dynamic analysis (IDA) was conducted on the subway station structure by using the ground motion input method based on viscoelastic boundaries. The results of IDA were then used to comprehensively evaluate 37 seismic intensity indices in terms of their effectiveness, practicality, and benefit. Based on this evaluation, seismic intensity indices that were suitable for the site conditions and structural configuration of the subway station were selected. Seismic fragility curves and damage state probability curves for the subway station structure were established using a double-parameter lognormal distribution model. These curves facilitated the determination of the probability of the subway station structure exceeding various performance levels and encountering different damage states under specific seismic intensities. The findings suggest that acceleration-related and velocity-related indices are more suitable as seismic intensity indices for predicting the seismic response of underground structures, while displacement-related and ratio-related indices are not appropriate. Under frequent seismic events, the probability of the subway station structure experiencing damage is relatively low. For design-level seismic events, the structure primarily sustains slight damage. In the case of rare seismic events, the subway station structure is more prone to slight and moderate damage. The results provide a reference for the seismic design of performance-based subway stations constructed on loess strata.

To address the irregular noise distribution and the high difficulty of semantic segmentation in railway yard catenary point clouds, and to enhance the detection of catenary anomalies. First, the railway yard catenary scene data is analyzed, and a knowledge framework is constructed for extracting catenary wire and rail top surface point clouds. Second, a segmentation and fusion filtering method is designed, considering the spatial characteristics of railway yard point clouds. Third, strong spatial semantic constraint rules are established to guide the fine extraction of wire features. The method was tested using WHU-TLS and other railway yard point cloud datasets. An experimental platform was built for analysis. The results show that, in complex environments with partial missing of point cloud data and noise interference, the proposed method is easy to operate and highly automated. Compared to traditional methods for extracting wire features, it requires the least time and achieves an average precision of ±5 mm in extracting contact wire features within a 100 m range, effectively supporting the intelligent detection of geometric features in railway station contact networks.

Rapidly obtaining co-seismic landslide distribution and conducting disaster assessments after earthquakes are vital for effective emergency relief and reconstruction. Therefore, in this study, the InSAR data-Newmark physical fusion driver model (IDNPM) was used to rapidly assess the landslides triggered by the earthquake in Jishishan, Gansu Province on December 18, 2023, with a view to quickly and accurately grasping the macroscopic distribution of landslide hazards. Firstly, through the time series SBAS-InSAR, it was revealed that there was serious gully development and retrogressive erosion in this area. These geological characteristics provided a favorable breeding environment for landslides. Secondly, the IDNPM was used to quickly evaluate the landslide of Jishishan earthquake, and it was predicted that the steep slopes and gully sides of Zhaomuchuan Village, Tashapo Village, and Dahejia Town were the high-risk areas for earthquake-induced landslide. Finally, based on the field investigation, numerical simulation, and satellite identification technology, the reliability of the model in practical application was proven. The results indicate that a total of 2.657% of the region is at high risk. There is a need to focus on such zones by urgently clearing and stabilizing slopes where landslides have occurred. For areas where no landslides have occurred, monitoring and assessment measures should be taken to guard against possible post-earthquake secondary landslide events. The research results can provide strong data support for emergency relief and reconstruction work after earthquakes in the affected areas.

Cr alloy seal ring and YG-6 cemented carbide seal ring were used to pair with impregnated graphite seal ring in a petrochemical pump at 300–400 ℃, respectively. It was found that the Cr alloy seal ring maintained good sealing performance for a long-term service, while gas leakage occurred to the cemented carbide seal ring after a short time of service. To explore the reasons for the difference in service performance of two kinds of alloy seal rings, the surface morphologies, chemical compositions, and mechanical properties of the failed seal rings were characterized, and their failure mechanisms were analyzed. The results show that the Cr alloy seal ring is made from martensitic Cr-containing steel without surface strengthening treatment, and the surface hardness and elastic modulus are 629.8 ± 14.2 HV30 and 244.7 ± 17.4 GPa, respectively. On its contact area with impregnated graphite, an annular wear scar characterized by a slight ploughing effect is observed, and the surface roughness of the wear significantly decreases. The surface hardness and elastic modulus of the cemented carbide seal ring are 1 475.3 ± 60.1 HV30 and 815.3 ± 57.2 GPa, respectively. There exists high residual stress and material embrittlement induced by oxidative corrosion in the seal ring surface. No obvious wear occurs on the contact area with impregnated graphite, but blocky defects caused by oxidation cracking appear. Due to low stiffness and high surface roughness, the Cr alloy seal ring suffers from abrasive wear on its surface with impregnated graphite, but the wear surface has grinding and polishing behaviors, maintaining its good sealing performance when paired with impregnated graphite. For the YG-6 cemented carbide seal ring, defects by cracking occur in the contact area with impregnated graphite under the action of the high surface residual stress and the material oxidation and embrittlement induced by high temperatures, resulting in sealing failure.

The rockfall events on transport lines in mountainous areas occur frequently and are sudden and random. Probability-based reliability design of protective structures is a necessary and effective means to reduce the hazard risk. However, the method of determining the design value of rockfall size, as a basic parameter of the design, is still unclear, making the reliability design fail to be carried out effectively. The prediction method of rockfall size and the return period was introduced based on the Poisson-generalized Pareto distribution (GPD) composite model. According to the rockfall record data of the Bai-upper section of Baoji-Chengdu Railway, the GPD threshold was selected, and the impact of the missing maximum and minimum rockfall sizes (vmax and vmin) in the record on the threshold selection and prediction results was analyzed. Corresponding to the exceedance probability of the standard value of earthquake action, a method of determining the design value of rockfall size was proposed, which was based on the three-level protection standard featuring “the structure doesn’t break under small rockfalls, can be repaired under medium rockfalls, and doesn’t collapse under large rockfalls”. The results show that the missing maximum rockfall size in the record has a small impact on the threshold selection but a large impact on the prediction results of the rockfall size. The prediction value of rockfall size corresponding to the return period increases exponentially with the set maximum rockfall size, while the recorded minimum rockfall size has less impact on both the threshold selection and the prediction results. By taking the record data of the Bai-upper section of Baoji-Chengdu Railway as an example, according to the selected reasonable threshold, different maximum rockfall size values are set. By using the method presented in this paper, the interval range of rockfall size in return periods of 50, 100, 1 000, and 10 000 years on the Bai-Upper section of Baoji-Chengdu Railway is predicted, and the standard value (design value) of rockfall size corresponding to the three-level protection standard in design reference periods of 50 and 100 years is calculated, which can provide a reference for similar engineering designs.

In view of non-uniform operation rules of ship locks and non-synchronous ship scheduling in the joint navigation scheduling of cascade hubs, a multi-dimensional nonlinear programming (MDNP) model considering ship priority was constructed with the comprehensive navigation efficiency of ships, the cost of waiting for lock opening, and the carbon emission as the decision-making objectives. Then, the improved backtracking multi-objective simulated annealing algorithm (IBMOSA) was used to solve the MDNP, and the optimization scheme for joint scheduling of cascade hubs was proposed. Finally, the effectiveness and reliability of the MDNP model and IBMOSA were verified by taking the “Three Gorges-Gezhouba” Cascade Hub as an example. The results show that the MDNP model can effectively take into account the navigation efficiency of ships and fairness, and IBMOSA has good convergence and global property. At the same time, through the coordinated drainage sluice plan formulation, the opening of each lock is reasonably arranged, which avoids the phenomenon of switching operation of cascade locks and reduces the overall dam crossing time of ships. Compared with that of the original scheduling scheme, the optimization efficiency of the three decision-making objectives of the joint scheduling scheme is nearly 40%, and the traffic congestion relief rate of cascade hubs is about 16%, which effectively solves the navigation contradiction among cascade hubs and improves the overall navigation efficiency of the Three Gorges water area.

The 5th generation mobile communication technology (5G) has advantages such as a high connection rate and large system capacity, which can support the development of marshalling station communication systems. However, the 5G antenna parameter planning is challenging due to the large amount of calculation, and it is difficult to achieve both high efficiency and accuracy simultaneously. Therefore, Based on the CloudRT ray-tracing (RT) platform, the signal coverage scenario was simulated. By considering the problem of angle selection and power optimization of communication base station antenna, a planning method based on a machine learning algorithm was proposed. Firstly, based on the overlap complexity and the clustering algorithm, the antenna angle parameters were clustered, and the clustering results were evaluated. Secondly, according to the relationship between antenna gain and angle, the optimization algorithm was designed to simplify the selection process of antenna angle parameter combinations. Finally, the simulated annealing operator was introduced into the genetic algorithm to solve the optimal power combination, and Jiangcun Marshalling Station was taken as the scenario for verification. The results indicate that the total power derived by the proposed method is 5.6 dB higher than that of the traversal algorithm, and the time required is only 13.5% of the traversal algorithm. It achieves high efficiency and accuracy simultaneously, which is expected to be applied to the 5G system of high-speed railways and marshalling stations.

Finite element model simulation of the pantograph and overhead conductor rail (OCR) system is slow, and the time cost of calculation is high. Therefore, the simulation method and process of the pantograph and OCR system using three-dimensional contact formulation were improved. Firstly, the equation that needs to be calculated iteratively when solving the relative velocity of the contact pair between the pantograph and the OCR was replaced with an explicit equation that can be calculated directly based on the central difference method. Then, the OCR model was linearized at the static equilibrium state to avoid the time-consuming stiffness matrix assembly procedure and increase the efficiency when calculating the internal force of the OCR. Next, a lazy judgment strategy was used to estimate the contact state of the pantograph and the OCR to reduce the computational load. Finally, the computational efficiency and accuracy of the fast simulation method in different cases were analyzed. The results show that compared with the standard simulation method, the proposed fast simulation method can save 97.67% of computational time in the example of pantograph and OCR with 30 spans of 8 m, and the maximum error of contact force results is only 0.48%. With the increase in the model scale, the time saved by the fast simulation method increases sharply, and its computational efficiency advantage becomes more and more significant. Meanwhile, the errors of contact force results are all less than 1.0%. With the increase in the operation speed, the proportion of time saved by the fast simulation method remains stable, and the errors of contact force results increase slightly. At speeds under 230 km/h, the standard deviation errors of contact force are all less than 1.0%.

In bridge health monitoring based on finite element models, Bayesian model updating techniques are commonly used to quantify the uncertainties of important parameters in the finite element models, so as to address the issue of non-uniqueness in model updating caused by measurement errors, modeling errors, computational errors, etc. To resolve the problem of low efficiency in model updating due to the large number of finite element simulations required, a Bayesian model updating method based on an adaptive nested sampling (ANS) algorithm was proposed. The method used the modal parameters to construct the probability objective function and adopted the ANS algorithm to approximate it. ANS retained the nature of nested sampling (NS), which made the samples ultimately approximate the optimal parameters by narrowing the sampling range layer by layer, and it simplified the computation process of the evidence value and the a posteriori probability density value by transforming the high-dimensional integration problem into a simple one-dimensional integration problem through layer-by-layer approximation. On this basis, the ANS algorithm could also reduce the call of the finite element model by adaptively adjusting the number of samples during the iteration process. Finally, a pedestrian truss bridge was used as a case study for Bayesian finite element model updating experiments. The results demonstrate that under the same algorithm parameter settings, the ANS algorithm reduces the number of finite element simulation calls by approximately 84% compared to the traditional NS algorithm. This leads to approximately 86% computational time savings while obtaining uncertainty updating results with equal accuracy.

To meet the demand for 5G communication in tunnels and increase the utilization rate of trackside antennas, a dual-band trackside antenna based on metamaterials was proposed, which could support both automatic train control systems and civil 5G wireless communication. First, a miniaturized dual-band trackside antenna was designed based on the 5G communication deployment scheme, and the finite element method was used to simulate the electromagnetic properties of the antenna before and after miniaturization. The impact on the electromagnetic environment and other radiation sources in the tunnel was evaluated. Second, a lightweight human body model containing important tissue such as the trunk, skull, brain, and heart was constructed, so as to compare the effects of radiation on the specific absorption rate (SAR) of human tissue between the simulated traditional single-band trackside antenna and the miniaturized dual-band trackside antenna. The results show that the miniaturized dual-band trackside antenna is 40% and 20% smaller than the traditional single-band trackside antenna when the antenna operates at 2.45 GHz and 3.40 GHz, respectively, and the electric field strength in the surrounding tunnel space is reduced by over 2.09% and 6.57%. The induced electric field strength on the leaky coaxial cable is reduced by 19.67% and 32.41%, respectively. The miniaturization of the antenna effectively reduces the impact on surrounding radiation sources and improves the electromagnetic compatibility of the trackside antenna inside the tunnel. The miniaturized dual-band trackside antenna makes the SAR values absorbed by the trunk, skull, brain, and heart of the human body drop by 19.76%, 46.60%, 55.62%, and 55.28%, respectively, which significantly decreases the radiation impact of the trackside antenna on occupational groups.

In order to solve problems of slow system response speed and poor anti-interference ability in the position control of the rotor of active magnetic bearings (AMBs), a position control method combining the non-singular fast terminal sliding function with the improved super-twisting reaching law was proposed to obtain fast and accurate control effects of dynamic responses. In addition, due to internal and external interference in the system, constant switching gain was added to the sliding mode reaching law, so as to ensure the robustness of the system, but it could exacerbate the system chattering. Therefore, the interference was observed and compensated by a nonlinear extended state observer, which alleviated the contradiction between chattering and anti-interference. Then, the stability of the proposed method was proven Lyapunov stability theory, and the proposed control method was verified by simulation and experiment. The results show that compared with the traditional sliding mode controller, the designed controller has faster response speed and stronger chattering suppression ability, and the time for the rotor to reach the target position is shortened by 56.4%. The dynamic performance of the system is improved, and the average control current is reduced by 68.5%. The chattering suppression ability of the system is enhanced, indicating that the proposed algorithm has strong robustness.

The positioning and lowering construction of large prefabricated steel caissons for cross-sea bridges is facing significant threats from the complex marine environment, including extreme waves and currents. In-depth research on the dynamic characteristics of the steel caisson during the positioning and lowering process under wave and current effects is of great importance for the positioning accuracy, lowering stability, and construction safety of steel caissons. Based on the LS-DYNA finite element program, a three-dimensional full-scale steel caisson fluid-structure coupling model under the action of wave and current was established. By comparing with the second-order Stokes wave analytical solution and the experimental results of the existing flume coupling experiment, the accuracy of the three-dimensional fluid-structure coupling model was verified. Subsequently, the validated model was used to investigate the influence of wave parameters, flow parameters, anchor cable arrangement, and structure lowering position on the wave and current loads and dynamic characteristics during the positioning and lowering process of the steel caisson. The research results indicate that the proposed anchor cable arrangement can effectively reduce the displacement and inclination of the steel caisson structure under different wave and current conditions, with a maximum inclination angle of no more than 2°. Compared with the individual effect of currents, the maximum horizontal force, horizontal displacement, and inclination angle of the steel caisson caused by the combined effect of waves and currents are increased by at least about 86.34%, 25.15%, and 112.96%, respectively. As the submergence depth of the steel caisson increases, the maximum horizontal force and horizontal displacement experienced by the steel caisson increase by approximately 41.90% and 50.62%, respectively, while the maximum inclination angle of the steel caisson decreases by approximately 31.06%. In the study of the positioning and lowering process of the steel caisson, the influence of wave and current loads and displacements on the structure at different lowering depths should be fully considered, so as to provide a reliable theoretical basis for analyzing the stability of the steel caisson in the process of positioning and lowering.

In order to improve the force performance and durability of assembled bridge piers, it was proposed to adopt the assembled bridge piers with hybrid connection of cast-in-place fiber-reinforced engineered cementitious composites (ECC) and assembled mortise and tenon joints and carry out the pseudo-static tests of the bridge piers with different design parameters (depth of the groove and thickness of the cast-in-place ECC layer), so as to establish the experimentally-validated ABAQUS finite-element model. In addition, extended parametric analysis was carried out, and theoretical derivation was conducted on the basis of the finite element parametric analysis. The calculation method of the eigenvalue of the skeleton curve and the restoring force model of the hybrid-connected assembled RC bridge pier were proposed. The results show that the damage mode of the three bridge pier specimens is compression bending damage, and the cast-in-place ECC section of each specimen is not damaged; the changes in the depth of the groove and the height of the cast-in-place ECC section have significant effects on the ductility coefficient and ultimate displacement of the bridge piers. The results of the theoretical analysis coincide with the results of the finite element analysis. The ratio of the calculated values of the formulas to the values of the finite element analysis ranges from 0.85 to 1.14, except for peak displacement, and the results are reliable; the hysteresis curve calculated by the hybrid-connected assembled bridge pier restoring force model matches well with the test curve, which can be used for the elastic-plastic calculation of bridge piers.

In order to further study the influence of site effects from engineering ground motion, a comparative analysis of site effects from ground motion in the Sichuan strong earthquake area was carried out based on two empirical methods, namely, horizontal-to-vertical spectral ratio (HVSR) and linear inversion. Firstly, 233 sets of strong motion waveforms captured by 17 strong motion stations during the aftershocks of the Wenchuan Earthquake were selected based on the magnitude, station, distance from the epicenter, and other factors. Second, the linear inversion method was used to estimate the quality factor Q_s of the S-wave based on the hinged three-stage attenuation model in the Longmenshan area. Meanwhile, two methods, rotational HVSR and multidirectional HVSR, were applied to explain the mechanism of the site effect of azimuthal angle on HVSR in seismic wave propagation. Finally, the possible reasons for the variability of the site effects calculated by the linear inversion and HVSR methods were analyzed, based on which an improved HVSR method was proposed to improve the accuracy of the site effect assessment. The results show that the quality factor of the S-wave in the area is frequency-dependent and approximately equals to 199.2f ^0.8 in the range of 0.4–20.0 Hz. The results of HVSR may have a certain dominant direction, and the site effect may increase suddenly at a certain angle with the change of the azimuthal angle, which may be related to the anisotropy of the soil layer at the site. The amplification of vertical ground motion, i.e., the vertical site effect formed by the coupling of soil layer at the site, engineered bedrock, or middle and deep hard rock layers, is the main reason for the difference between HVSR and linear inversion methods.

The service environment of alpine electric multiple units (EMUs) is affected by temperature for a long time, and the vehicle suspension element parameters and under-rail parameters have strong seasonal variation characteristics. To investigate the influence of temperature-varying characteristics of rubber elements on the operating performance of alpine EMUs, a multi-body dynamics model of alpine EMUs was established to analyze the vehicle dynamics characteristics under different temperatures. Then, the wheel wear characteristics at different temperatures were analyzed by the Jendel wear model. Finally, the wheel surface fatigue index was proposed based on the fatigue prediction model. The results show that the temperature variation will change the stiffness and damping value of suspension parameters, and the stiffness of suspension parameters increases as the temperature decreases. The dynamic performance of the EMUs decreases at low temperatures. The wear of the vehicle increases as the temperature decreases. After 200 000 miles of operation, the largest depth of wheel wear is found at a temperature of −40 ℃, which is 6.2% greater than the depth of wheel wear at a temperature of 20 ℃. The surface contact fatigue index gradually increases as the temperature decreases, with wheel surface fatigue indexes being 6.4648×10⁻⁴, 6.6150×10⁻⁴, and 6.7885×10⁻⁴ at temperatures of 20 ℃, −20 ℃, and −40 ℃, respectively. Temperature-varying characteristics have a large effect on the suspension parameters of alpine EMUs, with dynamic performance deteriorating at low temperatures, wear intensifying, and wheel surface fatigue increasing.

Mining dump trucks are mainly used for small-scale mine transportation, often run on poor roads or with serious overloading and other conditions. Hydro-pneumatic suspension is widely used in large construction vehicles due to its nonlinear characteristics of stiffness and damping, which can better adapt to external load excitation changes. For the XDR80t mining dump truck produced by XCMG, the acceleration data of the tire center of mass and body were collected, and a method based on frequency domain integral was proposed to obtain the relative displacement data of the piston rod. AMESim simulation platform was used to establish a mechanical and hydraulic co-simulation model, and the variation trend of body vibration characteristics under different structural parameters of suspension was investigated. The results show that the damping hole diameter has a more obvious influence on the vibration state of the body. When the damping hole diameter is changed from 8 mm to 14 mm, the peak value of acceleration is reduced by about 49.27%, and the root mean square (RMS) value is reduced by about 49.42%. However, the pitch angle shows an increasing trend. With the increase in cylinder/rod diameter from 180/150 mm to 200/170 mm, the peak value of acceleration and RMS value decrease by 16.84% and 18.62%. When the pre-charge pressure is increased from 1.5 MPa to 2.25 MPa, the peak value of acceleration and RMS value decrease by 27.67% and 27.49%, and the pitch angle declines.

Since it is difficult to accurately select representative super-high-dimensional random phase angles, the good lattice point with power generator method (GLPPGM) was utilized to generate samples of representative track irregularities, which were applied to the vehicle-bridge system to obtain the mean and standard deviation of random dynamic responses. Then, the calculation accuracy and efficiency of this method were explored by comparing the results of the pseudo-excitation method, deterministic time history method, and Monte Carlo method (MCM). Finally, the threshold value of the derailment factor considering the daily operation volume of trains was studied by using linear and nonlinear wheel-rail contact relationships. The Harmony train passing over a bridge was studied, and the results show that compared with that by the MCM, the uniformity between the samples of track irregularities generated by the GLPPGM in different directions is better. The probability characteristic parameters of the random dynamic response obtained by the GLPPGM have higher calculation accuracy than different methods, and its calculation efficiency is nearly five times higher than that of the MCM. When linear and nonlinear wheel-rail contact relationships are considered, the threshold value of the derailment factor differs by 4.68%, and the GLPPGM has a wider applicability.

In order to reveal the influence laws of the initial curvature of members on the stability bearing capacity of suspended domes, a nonlinear buckling analysis of suspended domes was carried out by applying the multi-beam method to simulate the initial curvature of members and the random imperfection mode method to introduce the initial curvature of members with different shapes and amplitudes. The overall imperfection and the initial curvature of members were introduced to investigate the effect of the two kinds of imperfections imposed jointly on the structural stability behaviors. The results show that the mean coefficients of stability bearing capacity of suspended domes are significantly reduced when only the initial curvature of members is considered, and the maximum reduction is 33.84%, which indicates that the structure is sensitive to the initial curvature of members. Compared with the sinusoidal full-wave, the sinusoidal half-wave as the shape of initial curvature is more unfavorable to the structural stability. When the overall imperfection and the initial curvature of members are both considered, the coefficients of stability bearing capacity are further reduced for the suspended domes compared with the perfect structure, with the maximum reduction being 44.80%, but the reductions are smaller than the sums of reductions when the two kinds of imperfections are introduced separately. The joint action of the two kinds of imperfections has coupling effects on the structural stability bearing capacity, which weakens the adverse effects when the two kinds of imperfections are introduced separately to some extent.

In order to study the damage characteristics of meso and micro pore structures of gypsum rock subjected to freeze-thaw cycles in cold regions, anhydrite rock was taken as the research object, and the porosity, pore size, and pore throat distribution characteristics of anhydrite rock were obtained based on nuclear magnetic resonance (NMR) experiments. According to fractal theory, the calculation formulas of the fractal dimension of pore size and pore throat of rock were derived, and the influence of freeze-thaw cycles on the fractal dimension of pore structures of anhydrite rock was discussed. The relationship among different pore structures, fractal dimensions of pores, and porosity was established, and the pore structure types that had a greater impact on porosity were revealed. The results show that the pore size of anhydrite rock under freeze-thaw cycles presents a “three-peak” distribution. With the increase in freeze-thaw cycles, the micropore (r ≤ 0.100 μm), PT-Ⅰ (r∈(0, 0.100) μm) of pore throat, fractal dimension of pore (D_P), and fractal dimension of pore throat (D_PT) decrease exponentially. While, the mesopores (r∈(0.100, 1.00) μm), macropores (r ≥ 1.000 μm), PT-Ⅱ(r∈(0.100, 4.00] μm) of pore throats, and porosity increase exponentially. It can be concluded that larger pores, as well as smaller pore throats and fractal dimension of pore throats, have a greater influence on the porosity of anhydrite rock.

For the compressive sensing algorithm, the correlation between measurement matrix and sparse base always determines the accuracy of signal recovery. In order to improve the performance of the compressive sensing algorithm in signal reconstruction in large-scale communication scenarios, the measurement matrix was improved based on matrix decomposition and equiangular tight frame (ETF) theory. Firstly, a dictionary matrix was constructed based on the measurement matrix and sparse base, and a Gram matrix was constructed. Eigenvalue decomposition was used to reduce the average correlation of the Gram matrix. Then, based on the ETF theory and gradient reduction theory, the Gram matrix was pushed to approach the ETF matrix to reduce the maximum value of the non-principal diagonal elements of the Gram matrix and the maximum correlation between the measurement matrix and the sparse basis. The orthogonal matching pursuit (OMP) algorithm was used as the reconstruction algorithm for simulation and verification, and the simulation results show that after optimization, the correlation coefficient of the matrix is reduced by 40%–50%. In channel estimation and active user detection, the estimation error of active user number by the proposed algorithm is more than 50% lower than that by other optimization algorithms under high sparsity; compared with other matrices, the mean square error of channel estimation is improved by 3 dB, and the bit error rate performance is improved by 2 dB.

The large eddy simulation (LES) method was applied to transiently simulate the wavy vortex field within the annular gap in Taylor-Couette and investigate the variation of fluctuations between wavy vortices. The wavy vortex field within the annulus gap was investigated from both two-dimensional and three-dimensional perspectives. The results indicate that the velocity vector field on the meridian plane of the two-dimensional wavy vortex field within the annular gap exhibits periodic fluctuation characteristics. The velocity vector field remains essentially the same at the beginning and end moments of the cycle. The axial velocity direction at the vortex junction changes constantly and periodically, while the radial and tangential velocity directions remain constant. The velocity values of the vortex pairs are greater than those of the vortex pairs inside the vortex, and the mainstream liquid transfer mainly occurs between the vortex pairs in the outward flow. Additionally, the fluctuation phenomenon of the three-dimensional wavy vortex field is clearly evident and exhibits periodic characteristics. The cycles for each working condition (10, 20, 30, and 40 r/min) are 12.94 seconds, 6.80 seconds, 1.93 seconds, and 1.49 seconds, respectively. With the increase in rotational Reynolds number, there is a significant decrease in vortex fluctuation amplitude and a reduction in the duration of fluctuations. The periodic flow transport of the mainstream liquid between vortices within the annulus gap propels fluid microclusters to perform a spiral-coupled vortex rotation around the inner cylinder within the annulus gap.

In the electric truck route planning problem with time windows, electric trucks may need to queue up when they go to charging stations for charging. To study the impact of different charging station configuration schemes on vehicle route planning and system performance, the queuing model was first built to describe the queuing phenomenon at charging stations. Then, a route optimization model was established by considering the power and flow constraints based on the electric truck route planning problem with time windows, with the queuing model of charging stations embedded into the optimization model. The optimization goals included minimizing vehicle power consumption costs, driver’s wages, penalty costs of time windows, and total costs of all charging piles. To solve the model, a hybrid heuristic algorithm combining mileage saving (C-W) and improved large neighborhood search (LNS) was designed, and the system performance metrics of charging stations were obtained by a recursive algorithm. 18 sets of experimental results show that increasing the number of charging piles simultaneously can control the average queuing time of a vehicle for charging within 1–5 minutes and effectively reduce the total cost by 2.6%–21.0%; increasing the number of charging stations can reduce the queuing time but increase the total cost of the entire route; when the customer time window is short, or the service time is long, the change in the number of charging piles has a more significant impact on the satisfaction of the time window.

To obtain location information of onsite construction crew continuously with the consideration of dynamical changing, occluding, and high appearance similarity in construction scenes, a computer vision-based location information perception method for onsite construction crew was proposed. Firstly, a deep learning-based object detection method was utilized to percept targets preliminarily. Then, a data association method based on person re-identification was used, where ID assignment was completed by matching the deep learning-based feature. A distance metric method based on re-ranking was utilized to optimize the similarity measurement results, and the matching result was processed by using a buffering mechanism and a dynamical feature updating mechanism, so as to mitigate mismatch due to difficulties in construction scenes. 2D coordinates and movement information corresponding to ID were obtained using perspective transformation of images to provide basic data for productivity analysis. Finally, standard test videos were created from images collected at different construction stages to test the proposed method. The test results show that in different scenes, the average F1 score of ID (IDF1) and multiple object tracking accuracy (MOTA) of the algorithm are 85.4% and 75.4%, respectively. The proposed re-ranking method and post-processing mechanism for matching effectively improve the tracking accuracy. Compared with the algorithm after removing these optimization mechanisms, the average improvement of IDF1 and MOTA is 52.8% and 3.8%, respectively.

Rail grinding occurs when the rail grinder is in traveling status, which is affected by the dynamic performance of the vehicle. Rail grinding is generally set as constant power grinding, involving a wheel-track contact relationship, wheel-track grinding relationship, hydraulic system, and control system. It is a mechanical-electric-hydraulic coupling process. The whole model of rail grinding based on mechanical-electric-hydraulic coupling was formed by considering the mechanical-electric-hydraulic coupling of the rail grinding process on the basis of vehicle-track coupling dynamics. This model included a vehicle-track coupling dynamics submodel, wheel-track contact submodel, grinding submodel, and hydraulic system submodel. This rail grinding model was validated by comparing it with experimental data. The results show that in vehicle-track dynamics model verification, the maximum deviation of derailment coefficient is 11.11%, and the maximum deviation of wheel unloading rate is 7.69%. The maximum deviation of the lateral force of the wheel is 11.68%. In hydraulic and control model verification, under 0.7 Hz and 1.7 Hz rail corrugation, the deviation range of pressure in the rodless cavity are between (−2.96%–2.92%) and (−0.32%–1.38%), and the deviation range of flow in the rodless cavity are between (−24.11%–0) and (−48.72%–0). In grinding model verification, the trend is generally consistent, with a deviation of 0.036 mm at the point of maximum deviation. The above deviations are all within the acceptable range, proving that this model can be applied to practical rail grinding study.

Hazard susceptibility assessment is generally a probabilistic modeling based on the spatial distribution characteristics of hazards, but the hazards have spatial heterogeneity. In order to solve the spatial heterogeneity of hazards, the collapses and landslides along the Wenchuan-Lixian section in the Wenchuan-Maerkang Expressway were studied. By using the K-mean algorithm, the hazard-threaten objects (people and property) and risk degree (damaged house area and damaged road length) in the study area were spatially clustered, and different clustering attributes were assigned to the study area. Then, nine factors including slope angle, elevation, slope aspect, curvature, surface cutting degree, river curvature coefficient, distance from the tectonic zone, bank slope structure, and formation lithology were selected in terms of hydrology, geology, and geomorphic conditions. The samples were divided into 70% training data and 30% test data. The performance of the K-RF model and the traditional random forest (RF) model in susceptibility assessment was compared to provide theoretical support for operation safety and hazard prevention of expressways. The results show that the K-RF model contains a total of 82.95% of the hazard points in the areas with extremely high susceptibility, which has better assessment results than the single RF model (with AUC value increased by 5.4%). Therefore, it is feasible to use clustering to solve the spatial heterogeneity of hazards. However, the research limitation is that it fails to reflect the spatial heterogeneity of hazards from the hazard itself. The coupled model is a comprehensive reflection of susceptibility and vulnerability in essence.

To find out the shear bearing capacity and its calculation method of ultra-high performance concrete (UHPC) keyed joints, a full-scale model test of five UHPC keyed joints and a UHPC flat joint were carried out with the joint type and lateral compressive stress as parameters. The failure mode and the variation of shear bearing capacity of the specimens with UHPC joint were studied. Then, based on the shear-compression strength criterion of concrete, the octahedral stress formula was used to derive the formula for calculating the shear bearing capacity of UHPC keyed joints, which was then validated by the test results. Finally, the experimental data of 62 UHPC keyed joints were collected and used to verify the accuracy of the developed formula. The results show that the UHPC keyed joint is damaged by vertical major cracks developed at the root of the keys and has obvious brittle characteristics. The ultimate load of the specimen with an epoxied joint is greater than that with a dry joint by 21.3% under the same lateral compressive stress. When the lateral compressive stress increases from 3 MPa to 12 MPa, the ultimate load of the specimen with an epoxied joint increases by 26.9%. The developed formula can accurately predict the shear bearing capacity of UHPC keyed joints with low dispersion and conservative results in general. The average absolute errors of the specimen with five keyed joints are 11%, and those of 62 existing specimens are 21%.

In order to study the influence of frictional self-excited vibration of a pantograph-catenary system on the contact loss between the carbon strip and contact wire, a finite element model of the pantograph-catenary system at the rigid and flexible transition section of a metro was established based on the theory of frictional self-excited vibration. The complex eigenvalue analysis method was used to study the influence of different pantograph-catenary parameters on the frictional self-excited vibration of the system. The analysis results show that the main frequency of contact line corrugation caused by frictional self-excited vibration of the pantograph-catenary system is 399.61 Hz. When the friction coefficient is greater than or equal to 0.11, the pantograph-catenary system has unstable vibration, and with the increase in the friction coefficient, the unstable vibration tends to be stronger. The normal contact force, the contact position between the carbon strip and the contact wire, and the stiffness of the pantograph bow spring have great influences on the occurrence of the frictional self-excited vibration of the pantograph-catenary system. When the friction coefficient is less than 0.11, selecting the appropriate normal contact force or adjusting the stiffness of the pantograph bow spring can restrain or even eliminate the frictional self-excited vibration of the pantograph-catenary system and then reduce the contact loss caused by the friction between the pantograph and catenary.

To analyze the wind-resistance working mechanism of stretched ribs mounted on high-rise buildings, the impact of horizontal ribs on the flow field and wind load of high-rise buildings under atmospheric boundary layer flow was evaluated by using the large eddy simulation (LES), and the wind-resistance effect of different types of horizontal ribs was compared. The results show that the horizontal ribs significantly inhibit the formation of the separated vortex near the sidewall and elongate the wake vortex. The ribs obviously suppress the vertical flow near the buildings and induce a local vortex near the ribs, which eventually causes significant changes in the pattern of near-wall flow. The changes in the flow field will lead to corresponding alterations in wind pressure distribution and wind load. The horizontal ribs can cause a “zigzag” pattern distribution of the mean wind pressure coefficient along the altitude of the buildings, and the ribs significantly reduce the mean and fluctuating wind pressure on the sidewall. The maximum reductions are about 20% and 17%, respectively. With regard to total wind load, the horizontal ribs have negligible impact on the mean drag, while they can significantly mitigate the fluctuating lift on the buildings, with a maximum reduction of 27%. The effect of the rib arrangement on the aerodynamic characteristics is also significantly different. The continuous horizontal ribs affects the wind pressure distribution and wind load by changing the near-wall flow and the vortex structure, while the influence of discontinuous ribs on wind load is relatively weak.

To study the characteristics of the seepage-stress field and the safety of the lining structure of small interval tunnels under asymmetric seepage boundary conditions, based on the Liantang Tunnel in Shenzhen, China, a seepage model experiment for the small interval tunnels was developed. In addition, through model experiment and analog simulation, the distribution law of seepage water pressure in the surrounding rock of the small interval tunnels under unilateral water source conditions was analyzed, and the evolution law of the seepage field and the safety of the lining at different distances from the water sources were revealed. The results indicate that the surrounding rock seepage field of the small interval tunnels exhibits a significant asymmetric distribution under unilateral water source conditions. The water level decreases nonlinearly from the water replenishment boundary to the other side. Besides, the water pressure in the surrounding rock near the tunnels is distributed in an asymmetric “W” shape. The asymmetric distribution of the surrounding rock seepage field leads to the asymmetry of water pressure, water inflow, and safety coefficient in the left and right tunnels. Compared with the tunnel farther from the water source, the average water pressure and water inflow of the tunnel closer to the water source increases by 10.4% and 5.5%, respectively, and the safety coefficient decreases by 3.0%. Moreover, the water pressure asymmetry of the tunnel closer to the water source is more significant. The asymmetry of water pressure distribution in the surrounding rock and lining slightly increases from the construction period to the operation period. As the distance from the water sources increases, the water pressure of the lining linearly decreases, and the safety coefficient and the asymmetry coefficient of the water pressure increase. The research results can provide a reference for the construction and operation of tunnels with asymmetric seepage boundaries in water-rich areas.

To explore the water-stop performance of a large-scale high-pier aqueduct under earthquakes, a finite element model of the aqueduct was established based on the fluid-solid coupling method, and the nonlinear coupling behavior of the aqueduct and water under dynamic effects was simulated. By introducing the deformation and failure threshold of the water-stop, the failure process between the aqueduct spans was reproduced, and the overflow of the water body in the aqueduct after the water-stop failure was revealed. Based on an actual high-pier aqueduct structure, the macro- and micro-seismic response of the aqueduct was obtained through nonlinear dynamic analysis, including pier strain, bearing displacement, and water-stop damage. The impact of different bearing types and seismic isolation devices on the seismic performance of aqueducts was revealed. The research results show that under rare earthquakes, severe structural damage will not occur to the piers and the aqueduct, and the structural safety of the aqueduct under earthquakes is guaranteed. However, under designed earthquakes, the water-stop of the aqueduct will fail, which cannot guarantee that the aqueduct will maintain the water diversion function after an earthquake. Adding steel dampers can effectively control the deformation of the aqueduct spans, ensuring that the water-stop of the aqueduct will not be damaged under a designed earthquake. However, the water-stop will inevitably be damaged under rare earthquakes, and the deformation control of the aqueduct spans under strong earthquakes still faces challenges.

Rock strength is a critical parameter for assessing rock stability and safety. Efficient and accurate prediction of rock strength can effectively guide tunnel excavation and support. Digital drilling parameters and mechanical property data of rock were collected from various devices. By analyzing energy transfer during the drilling process, a quantitative relationship between digital drilling parameters and uniaxial compressive strength (UCS) was established. Meanwhile, machine learning methods were employed to develop a rock strength prediction model based on drilling parameters. Four algorithms, including a back-propagation (BP) neural network, random forest, convolutional neural network (CNN), and long short-term memory network were chosen to compare their prediction effects and identify the optimal model. The results indicate that compared to the theoretical formulas and the other three machine learning algorithms, the BP neural network algorithm excels in rock strength prediction, with a root mean square error of 5.794, a mean absolute error of 4.129, and a correlation coefficient of 0.9749.

To investigate the trackbed bearing capacity and lateral resistance characteristics of a new X-shaped sleeper, scaled tests comparing the stiffness and lateral resistance between X-shaped and Type Ⅲ sleepers were conducted. A 3D model of a ballast track was established by the discrete element method to analyze the vertical load transmission mechanism and lateral resistance of these two types of sleepers at a micro level. The results indicate that at the maximum vertical load, the X-shaped sleepers significantly reduce vertical displacement (stiffness) by approximately 26.3% compared to Type Ⅲ sleepers (an increase of about 46.6%). Furthermore, the ultimate lateral resistance of the X-shaped sleeper is increased by 22.4%, which effectively improves the lateral stability of the track. The X-shaped sleepers exhibit a substantial increase in the contact area and stress with ballast between the sleepers. The contact forces on the X-shaped sleeper are distributed over four angular segments, making the ballast between the sleepers fully participate in the load sharing. Because the structure of the X-shaped sleeper can increase the participation of the ballast between the sleepers, the stiffness and transverse resistance of the trackbed are increased by about 29.2% and 31.6%, respectively, which is close to the experimental conclusion.

To study the formation mechanism of inner rail corrugation on the ladder sleeper track in the small-radius curve, a finite element model of the leading wheelset–ladder sleeper track system was developed based on the theory that self-excited frictional vibration triggered by saturated wheel-rail creep force causes rail corrugation. In this model, solid elements were used to model the fastening system. Complex eigenvalue analysis and transient dynamic analysis were applied to solve the motion stability and dynamic time-domain response of the wheel-rail system, respectively. Furthermore, the effects of the parameters of the cushioning pad and ladder sleeper structure on the self-excited frictional vibration of the wheel-rail system were studied. The results show that the self-excited frictional vibration with a frequency of 150 Hz caused by the saturated wheel-rail creep force is the cause of inner rail corrugation on the ladder sleeper track in the small-radius curve section. The predicted corrugation wavelength is 69 mm, which agrees well with the measured wavelength. Parameter sensitivity analysis shows that increasing the damping of the lateral cushioning pad and laying ladder sleepers with a spacing of 1.25 m between lateral steel pipes can suppress rail corrugation on the ladder sleeper track to a certain extent.

In order to solve the problem of difficult cutter layout on a W-shaped cutterhead for a shaft boring machine, the influence of cutter installation and arrangement parameters on the rock breaking effect of cutters was studied based on the discrete element method, and the overall layout optimization scheme of cutters was obtained by particle swarm optimization algorithm. Firstly, the two-dimensional discrete element model of the cooperative rock breaking of cutters at the depression area and the conical surface of the tunnel face was established, respectively. Then, the cooperative rock breaking effect of cutters with different cutter spacing at the depression area was studied, and the influence of different cutter spacing and tilt angles at the conical surface on the rock breaking condition, cutter load, and rock breaking efficiency was revealed. The reasonable cutter spacing and tilt angle at the conical surface were obtained by taking the specific energy of rock breaking as the index. Finally, it was found that the star-shaped layout was suitable for cutters on the special-shaped cutterhead, and the particle swarm optimization algorithm was used to optimize the cutter layout scheme. The results show that cutter spacing of cutters should be reduced at the depression area of the phyllite strata. When cutters on the special-shaped cutterhead at the conical surface adopt the vertical conical installation method, the rock breaking efficiency is higher. After the optimization of the cutter layout, the radial load of the special-shaped cutterhead is reduced by 24.07%, and the resultant moment of the cutterhead is reduced by 40.83%. The research results can provide a reference for cutter layout on the special-shaped cutterhead in shaft engineering.

In order to study the injection law of each nozzle hole of the common rail injector, an injection pattern measuring device for multi-hole injectors was developed based on the momentum method. Under different load conditions, the developed device was used to measure the injection rate of each nozzle hole of the injector, and the difference was compared with the measurement results of the commercial single injection instrument EMI 2. Under different injection pressures, the injection stability of the single injection hole was studied. The research findings indicate that at low injection pressure, the fluctuation rate of the injection decreases with increasing injection pulse width, with an overall fluctuation rate of 10%–20%. At this point, the needle valve cannot fully open, leading to significant fluctuations in the injection due to unstable fuel flow between the needle valve and its seat. At high injection pressure, the needle valve is more likely to reach maximum lift, and thus the inconsistency in nozzle hole parameters becomes the key factor causing fluctuations in the nozzle hole injection. Within the range of injection pulse width of 0.5–2.0 ms, the fluctuation rate of the injection is within 5%, much lower than the fluctuation rate of nozzle hole injection under low injection pressure conditions. This indicates that the inability of the needle valve to reach maximum lift is the primary cause of injection instability in common rail injectors.

The brake disc of electric multiple units (EMUs) will form complex residual stress during long-term service, which will lead to irreversible warping deformation after disassembly. In order to investigate the influence of residual stress and warping deformation on the feasibility of subsequent maintenance and reuse of brake discs, firstly, the Ramberg-Osgood constitutive model of corresponding materials was constructed by testing the tensile stress-strain data of cast steel for wheel-mounted brake discs of EMUs at different temperatures. A cyclically symmetric three-dimensional transient numerical simulation model of brake discs was established in finite element software. Secondly, the formation and balance process of residual stress in the surface and center of the brake disc were analyzed by indirect coupling method for different braking conditions considering different initial braking speeds and different average decelerations of the train. The change in warping deformation of the brake disc after structural constraint release was studied. The functional relationship between brake disc deformation and braking energy and heat input power was fitted by piecewise function and polynomial. Finally, by measuring the warping deformation and testing the X-ray residual stress of the brake disc after service, the residual stress distribution law on the friction surface of the brake disc under the corresponding simulation condition was compared. The simulation results had good data and trend consistency with the measured data. The study reveals that the warping deformation of the brake disc is positively correlated with braking energy and braking deceleration. More severe braking condition indicates greater warping deformation of the brake disc. The simulation and measurement show that the high residual tensile stress is located in the middle of the friction surface and close to the bolt holes. The high residual tensile stress value is higher when the braking condition becomes more severe.

To study the reason for the abnormal fracture of e-type clips on small-radius curved subway tracks, the development of rail corrugation on Line X of the Chengdu Metro over an extended period was monitored and measured. Based on the theory of friction-induced self-excited vibration, a comprehensive solid finite element model of the wheelset−rail−fastening system was established. The effects of short-pitch rail corrugation and long-pitch rail corrugation on the vibration fatigue life of e-type clips were studied by means of implicit dynamic analysis and harmonic response analysis. The study reveals that both types of rail corrugation result in a decrease in the vibration fatigue life of the e-type clips. Greater amplitude of rail corrugation indicates shorter vibration fatigue life of the clips. Rail corrugation can not only induce the e-type clip to generate forced vibrations at the frequency matching that of the rail corrugation but also easily trigger vibrations at multiples of this frequency in the e-type clips. For short-pitch rail corrugation, due to the existence of a frequency twice that of the rail corrugation, the rail corrugation with wavelengths of 25 mm and 40 mm is most likely to lead to vibration fatigue failure of the e-type clips under the influence of short-pitch and long-pitch rail corrugation with the same wave depth amplitude. When the wave depth amplitude of long-pitch rail corrugation with a wavelength of 120 mm is large, the vibration fatigue life of the clips decreases sharply due to the excited 6-fold vibration. However, the long-pitch rail corrugation with a wavelength of 240 mm has only a limited impact on the vibration fatigue life of the clips due to the attenuation of vibration intensity.

To effectively evaluate the reliability level of the LS-FA-211001 suction anchor during application, the cumulative effect of external loads was considered, and a time-dependent reliability model was established under cyclic loads. The time-dependent reliability analysis of the suction anchor was carried out based on the quantified uncertainty data. The Monte Carlo simulation (MCS) method was adopted to verify the reliability of the suction anchor. The results show that the life of LS-FA-211001 suction anchor can reach 100 times even in harsh exploratory points under the reliability of being over 95%. At the same time, under different cycles of load, the error of the time-dependent reliability model of the suction anchor established in this paper is less than 2.15% compared with the reliability results evaluated by the MCS method, which verifies the effectiveness of the proposed method.

To investigate the feasibility of laying seamless turnouts in plateau areas and the influence of plateau climate on the stability of seamless turnouts across areas, the effect of stress-free temperature difference on the force characteristics of seamless turnouts under different climates, elevations, and structural types was analyzed. First, based on the physic-geographical environment and operating conditions of railways in plateau areas, the typical seamless turnouts of the Qinghai−Xizang line during upgrading were selected as research objects, and then the parameter tests of key force transmission components with force characteristics in turnouts under different structural types were conducted, clarifying the influence of the low temperature of plateau climate on resistance force of fasteners and ballast beds. At last, the calculation model of seamless turnouts considering the multi-field coupling effect and plastic resistance force was established, and the relationship between stress-free temperature difference and stress deformation of seamless turnouts was revealed. The results show that when the temperature difference is high, the growth rate of temperature additional force induced by stress-free temperature difference increases from 4.5 kN/℃ (Daqiongguo Station) to 6 kN/℃ (Tanggulabei Station); the stress-free temperature difference between seamless turnouts and adjacent lines or adjacent turnouts has great impact on stress formation of seamless turnouts, and the growth rate of lateral displacement caused by the stress-free temperature difference of the line/turnout rail section increases from 0.010 mm/℃ (Daqiongguo Station) to 0.011 mm/℃ (Tanggulabei Station). The impact of the stress-free temperature difference between left/right or straight/side rails on turnout stability is small. In plateau areas, the turnout involves the locking of multiple strands of rail, which is easy to cause a large stress-free temperature difference. To increase safety redundancy, the stress-free temperature difference should be controlled within ±3 ℃, while that of the adjacent rail section should be no more than 5 ℃.

In order to evaluate the prediction accuracy of typical stress-dilatancy rules on the mechanical response of common geomaterials, propose a stress-dilatancy rule suitable for rocks, and improve the accuracy of the constitutive model, typical stress-dilatancy rules derived from experiment data were compared to propose a stress-dilatancy model suitable for rocks. Firstly, based on the thermodynamic framework and the energy conservation equation, three typical stress-dilatancy models were sorted out, and the stress-dilatancy data of various geomaterials were compared with the typical stress-dilatancy rules. Then, by taking the Rowe dilatancy model as the basic framework and considering the influence of many factors, an improved Rowe stress-dilatancy model suitable for rocks was proposed, and its fitting effect on the test data was analyzed. The simulation effect of the proposed model and the variable dilatancy angle model on the evolution of dilatancy angle during loading was compared. Finally, the modified Rowe dilatancy rule was coupled with the modified Cambridge model, and the simulation results and test data of the classical modified Cambridge model were compared and verified. The results show that the classical stress-dilatancy rule based on the pure friction hypothesis cannot accurately describe the stress-dilatancy response of geomaterials with cohesive force due to the influence of cohesive force. The modified Rowe dilatancy model can effectively reflect the stress-dilatancy response of rock and simulate the “turning hook” phenomenon in the data. Furthermore, the proposed stress-dilatancy model is not only simple in form but also has fewer parameters than the variable dilatancy angle model. The proposed modified Rowe dilatancy model can improve the accuracy of the constitutive model in deformation prediction.

To study the influence of automotive acoustic package design parameters on its multi-performance objectives, firstly, the traditional DBNs (deep belief networks) method was modified, and the SVR-DBNs (support vector regression-deep belief networks) model was proposed to improve the accuracy of model mapping. Secondly, from the perspective of vehicle noise transfer relationship and hierarchical target decomposition, a multi-level target prediction and analysis method was proposed. Finally, the proposed method was applied to the multi-objective prediction and optimization analysis of the MTL (mean transmission loss), weight and cost of the acoustic package for a real vehicle.The results show that the accuracy of SVR-DBNs method for the MTL, weight and cost target prediction of the acoustic package is higher than 0.975, which is better than that of the traditional BPNN（back propagation neural network）, SVR and DBNs models. The optimization results based on the SVR-DBNs model are appropriate to the measured results, the comprehensive relative error of the predicted and tested targets is 1.09% (the absolute values of the relative errors of MTL, weight and cost are 1.44%, 1.04% and 0.71%, respectively). Compared with the original status, the MTL, weight and cost of the acoustic package have increased by 5.51%, 9.01% and 4.40%, respectively.

With the increase in sinusoidal disturbance frequency, the performance of extended state observers (ESOs) will decrease. In order to improve the disturbance suppression ability of the ESO in the maglev rotor system, firstly, the mathematical model of a one-degree-of-freedom (1-DOF) maglev bearing rotor system was built. Secondly, ESO was designed, and the reasons for its reduced disturbance suppression effects were analyzed. On this basis, a model assisted ESO (MESO) was proposed to improve the bandwidth configuration and enhance the disturbance suppression effects. Then, the stability of the active disturbance rejection controller based on MESO was analyzed in the frequency domain. The effectiveness of the proposed observer was finally verified through simulation and experiments. The research results indicate that an increase in bandwidth amplifies the impact of system noises and increases the control voltage of the system. As the disturbance frequency increases, the suppression effect of MESO on high-frequency sinusoidal disturbance will decrease, but it can still reduce the modal amplitude of the rotor. After applying fundamental harmonic disturbance of 10 Hz−2 mm and fundamental impulse disturbance of 1g to the rotor at a rotating frequency of 50 Hz respectively, the rotor displacement under MESO control is reduced by 16.3% and 22.6%, respectively compared with that under ESO control, and the control voltage is reduced by about 14%.