In order to study the influence of the temperature-dependent material property on the wheel–rail contact behavior and frictional temperature rise, a three-dimensional wheel–rail thermal-mechanical coupling model considering the temperature-dependent material property was proposed in this paper, which could consider the longitudinal and lateral creepage rates and spins to simulate the service state of the wheel–rail system more realistically. In this paper, the influence of the thermal-mechanical coupling modeling method on the wheel–rail frictional temperature rise and contact stress was first studied. Subsequently, this model was applied to the simulation of vehicle–rail interaction of subways running on a small radius curve. The results show that when the temperature reaches 450 ℃, the wheel–rail contact stress is significantly reduced by 20%. After considering the thermal-mechanical coupling modeling, the predicted temperature rise of wheel–rail interface is significantly lower than that without considering the thermal-mechanical coupling modeling. When the creepage rate is 0.16, the difference between the two can reach 51%. Due to excessive creepage rate and spin, the wheel–rail frictional temperature rise will increase sharply to 750 ℃ when subways run on a small radius curve. Therefore, the wheel–rail thermal-mechanical coupling modeling should be considered to avoid overestimating the wheel–rail frictional temperature rise and wheel–rail contact stress.

The stiffness of the rubber pad of the WJ-8 fastener exhibits nonlinear characteristics during long-term service, and the static stiffness decreases with the increase in the load. In order to improve the calculation accuracy of the three-dimensional transient rolling contact finite element model, the LMA tread wheel and CHN60 rail were used. Based on the explicit integration algorithm, the linear elastic fasteners in the previous research were transformed into nonlinear fasteners to establish a three-dimensional wheel–rail transient rolling contact finite element model considering the nonlinear characteristics of fastener stiffness. The influence of stiffness nonlinearity on the high-frequency dynamic response and transient contact behavior between wheel and rail corrugation was studied, and the change of wheel–rail contact force and axle box acceleration in the time-frequency domain under corrugation conditions was analyzed. The results show that the nonlinearity of the fastener has an obvious effect on the change of the wheel–rail contact force. The main manifestation is that when the wheel travels to the front end of the fastener, the strong vibration makes the rubber pad soft, which reduces the contact force of the wheel and rail. In addition, when the wheel travels above the fastener, the vibration is weakened under the action of the axle load; the stiffness characteristic increases the wheel-rail contact force, and the difference between the wheel–rail force changes is up to 13.1%.

In order to study the maintenance mechanism of ballast tamping and stone-blowing from a micro view, a ballast box numerical model using the discrete element method was established, and the whole processes of ballast tamping and stone-blowing were visually simulated by coupling the tamping hammer model of multi-body dynamics and the blowing tube model of computational fluid dynamics. Based on the discrete element coupled numerical simulation, the effects of two ballast maintenance methods on ballast disturbance and sleeper settlement after operation were compared. The results show that the ballast disturbance and the average contact force of the ballast of the stone-blowing are less than those of the tamping, and the disturbance is mainly concentrated in the insertion stage. Moreover, the peak velocity and contact stress of ballast particles during the stone-blowing are only 37.5% and 38.9% of those during the tamping. After tamping, the compactness at the bottom of the sleeper is increased by about 13.6%, and the compactness of the upper and lower areas between sleepers is reduced by about 21% and increased by about 4.8%, respectively. After stone-blowing, the compactness at the bottom of the sleeper is increased by about 6.5%, and the compactness of the upper and lower areas between sleepers is almost unchanged. Due to the stone-blowing beneath the sleeper, the stone-blowing greatly improves the contact state and stress diffusion at the bottom of the sleeper. The contact number between the sleeper and the ballast particles increases by about 243%, which makes the load transfer more uniform. After 1 000 cycles of loading, the sleeper settlement after stone-blowing is reduced by about 18.1% and 44.4% respectively compared with tamping and unmaintained conditions.

According to irregular changes in rail profiles in a fixed-nose crossing, a parametric design method was proposed based on the B-spline theory by considering the section characteristics of rail profiles in a fixed-nose crossing. In addition, the rail profile fitting evaluation indexes and the influence weights of key control parameters on the rail profile fitting were proposed. With No.12 turnout of fixed-nose crossing of 60 kg/m rail as an example, the design of experiment (DOE) was employed to analyze the influence of railhead slope, rail side slope, and proportion coefficient of composite circular arc on the changes in the full railhead profile, rail top profile, and rail side profile of the nose rail. The results show that 1) for nose rail with a section of 20 mm, the influence weights of railhead slope, rail side slope, and proportion coefficient of composite circular arc on the full railhead profile change are 21.08%, 56.89%, and 22.02%, respectively, and the influence weights on the rail top profile change of the nose rail are 8.42%, 61.95%, and 29.63%, respectively. For nose rail with a section of 50 mm, the influence weights of the key control parameters on the full railhead profile change are 55.9%, 33.38%, and 10.72%, respectively. For nose rails with a section of 20 mm and 50 mm, the influence weights of the rail side slope on the rail side profile change are 76.82% and 66.04%, respectively. 2) When the nose railhead width is 20 mm, the influence of the rail side slope on the nose profiles is more than 50%. As the nose railhead width increases, the influence weight of railhead slope on full railhead profile gradually increases from 21.8% to 55.9%, while that of rail side profile and proportion coefficient of composite circular arc is reduced by 41.3% and 51.3%, respectively.

In order to study the internal forces and the damage of broad-narrow joint under a temperature rise, a detailed finite element model with the interface between old and new concrete is established on the basis of concrete damaged plasticity model and cohesive zone model. The damage parameters and stress under different temperature rises are calculated, and the effects of the concrete strength at broad-narrow joint and the narrow joint width are analyzed. The results show that the fracture at the junction between broad and narrow joints is a brittle tension failure, and the breakage of narrow joint is a gradual compression failure. Compared with the fracture at the junction between broad and narrow joints, the breakage of narrow joint has a greater impact on the structural stress. The vertical tension stress arising from the uneven geometry at the junction between broad and narrow joints is the main cause for the damaged broad-narrow joint. Increasing the broad-narrow joint strength reduces the longitudinal compression stress and the compression damage, but contribute less to the vertical tension stress and the tension damage. To reduce damage and improve strength, it is recommended to equate the widths for the broad and narrow joints and the strengths for the concrete at the broad-narrow joint and the slab.

The freeze-thaw damage evolution of asphalt concrete for waterproofing layer in high-speed railways (shorted as railway asphalt concrete) was investigated. Four kinds of composite polymerized railway asphalt concrete were prepared with different asphalt binders and aggregate gradations, and the deterioration of macro mechanical properties in multiple temperature domains under repeated freeze-thaw cycles was evaluated. Models of freeze-thaw damage evolution for railway asphalt concrete were constructed, and the damage degree under the action of repeated freeze-thaw cycles was calculated. The results show that the retained rate of mechanical properties of the four kinds of railway asphalt concrete is still above 80% after 10 freeze-thaw cycles. The low-temperature fracture energy index is the most sensitive to freeze-thaw cycles, which can timely reflect the deterioration of mechanical properties of railway asphalt concrete. The goodness of fit of all freeze-thaw damage evolution models for railway asphalt concrete that are constructed through statistical reliability theory is nearly 0.99.

To study the distribution law of welding residual stress of corrugated steel web girders, a three-dimensional thermo-elastoplastic model was established by finite element software, and the welding temperature field and stress field were numerically simulated by the finite element method using thermal and mechanical coupling analysis technology. Double ellipsoidal heat source and modified element material properties were used for energy input and weld filling, respectively. The simulation results were compared with the measured values. The results show that the residual stress distribution of corrugated steel web girders predicted by the finite element method has the same trend as the measured values. At the bending angle of the weld of the corrugated steel web girder, the residual stress fluctuates continuously in a certain range. The peak value of the residual stress in the bottom plate and web appears in the central area of the weld, which is 1.30 times and 1.26 times the yield strength of the material. respectively. The longitudinal residual tensile stress of the bottom plate decreases rapidly within 78 mm on both sides of the weld centerline and then slowly transitions to compressive stress. In addition, the compressive stress on the narrow side of the bottom plate increases linearly, and the maximum value is about 0.61 times the yield strength of the material. The compressive stress decreases linearly on the wider side of the bottom plate and is converted to the tensile stress at the edge. The analysis indicates that the welding speed has little effect on the residual stress distribution but has a significant effect on the peak value of residual stress. When the welding speed increases from 150 mm/min to 250 mm/min, the maximum residual stress in transverse and longitudinal directions increases by 27.11% and 5.88%, respectively.

The current analysis method for the main cable shape of a suspension bridge with a spatial cable plane involves solving complex differential equations for the main cable. However, this approach has certain drawbacks, such as the complicated form of constraint equations and the significant influence of initial values on iterative convergence. To address these issues and improve convergence in determining the main cable shape, the equivalent beam method was used, and geometric correlation equations between external loads and the main cable shape were derived. Subsequently, a two-stage analysis method was developed to solve the spatial main cable shape: During the rough calculation stage, decoupling processing minimized initial value requirements while obtaining accurate results with sufficient convergence. These results were then used as initial values in the precise calculation stage to iteratively calculate an exact solution for the spatial main cable shape. The feasibility and effectiveness of this two-stage analysis method were demonstrated through an example involving a pedestrian suspension bridge, and finite element software was used to verify the accuracy of calculation results. The research results demonstrate that the proposed method exhibits lower requirements for initial values and does not require the setting of initial values. The iterative process eliminates deformation compatibility conditions and stress-free length calculation, resulting in enhanced solving efficiency and rapid convergence towards obtaining an accurate solution for the main cable shape. This approach is suitable for analyzing the main cable shape of a single tower suspension bridge with a unilateral spatial cable plane.

To explore the repair mechanism and effect of pneumatic impact treatment on fatigue cracks of the steel bridge deck, the plastic deformation of the target material during the pneumatic impact treatment was studied based on kinetic theory, and the behaviors of crack surface closure under such plastic deformation were analyzed. Then, the local stress field in the closure part was investigated, and the stress response and its deformation under the applied load were discussed by numerical method. Fatigue tests were carried out to verify the repair effect of pneumatic impact treatment at last. The results show that the mathematical model proposed here is able to predict the impact depth. Large plastic deformation is observed on the material surface during the pneumatic impact treatment process, and the impact depth and transverse deformation are similar. When the relative transverse deformation of the crack fracture surface becomes larger than the crack width, the contact closure and compressional deformation can be found, which will introduce the contact stress at the closure part. This contact stress can resist the tension effect of the crack surface under applied load, reduce the stress intensity factor at the crack tip, and restrain the propagation of fatigue cracks, which is also proved by the tests.

The dominant factor impacting the dynamic performance of a train under a crosswind changes from wheel-rail interactions to the aerodynamic force, making the crosswind overturning risk the main threat to safe train operation. This study first analyzes the train overturning stability using a refined coupling model to reveal its sensitivity to the train model. On the basis of a frequency domain framework accounting for the modal characteristic, transfer functions between the wind turbulence and track irregularities and the overturning responses are derived. The mechanism of train crosswind overturning is then intuitively interpreted via a parameter analysis. The results show that the overturning behavior of a train is controlled by the rolling mode around the lower center of the car body and the floating mode of the car body and that the influence of the wind load is significantly greater than that of track irregularities. Under track irregularity excitation, the first modal response primarily arises from the alignment component, while the second modal response arises from the vertical component. Under a wind load, the longitudinal fluctuating wind component plays a major role. Increasing the train speed, wind velocity, and wind direction angle increases the dynamic response of the train and reduces the maximum allowable wind speed to safely run the train. An increase in the failure probability can reduce extreme responses and increase the wind speed for safe operation.

In order to study the influence of the scouring effect on the dynamic response of long-span bridges under the combined action of earthquake and wind, based on the established coupled vibration analysis model of earthquake-wind-vehicle-bridge, the p-y curve ( p is the soil resistance and y is the pile displacement) reduction method was used to consider the load-displacement relationship between the piles and soil with different scour depths, and the lateral support stiffness and length of pile foundation were updated according to the load-displacement relationship and scour depth. Thus, the influence of the scouring effect on the dynamic response of long-span bridges was considered, and the model was applied to analyze the scouring effect of Jiangshun Bridge. The results show that the foundation scour weakens the lateral constraint of the foundation soil on the structure, thus reducing the natural vibration frequency of the structure, and the maximum reduction of the natural vibration frequency of lateral vibration mode is 6.01%; under the action of the operational vehicle and wind load, foundation scour has little effect on the vibration response of the structure; after the earthquake, the foundation scour increases the lateral vibration of the structure, and the maximum increase in the extreme value of the lateral displacement response of the structure is 9.1%; the lateral displacement response spectrum increases accordingly, but it has little effect on the vertical vibration of the structure; foundation scour may reduce the response of lateral acceleration of vehicles, and the maximum reduction of the extreme value of the lateral vehicle acceleration response is 7.7%, but it has little effect on the vertical vibration of vehicles.

In order to study the damage evolution law of damaged reinforced concrete (RC) structures repaired with carbon fiber reinforced plastics (CFRP) under earthquake action and accurately quantify the damage status of repaired structures, a quasi-static test of 10 circular RC piers was carried out, eight of which were repaired by different CFRP reinforcement methods. The test results were studied based on eight typical earthquake damage models, and a two-parameter seismic damage model for RC piers repaired with CFRP was established, in which the reduction coefficient of material properties was introduced to analyze the initial damage to the structure. The damage degree of RC structures was quantified according to the experimental phenomenon and the improved damage model. The results show that when the damage index of the repaired pier is calculated by using the typical earthquake damage model, the damage index of the damaged specimens is generally too large, and the variation of the damage index of the same pier model is quite different. The development trend of the damage index is not consistent with the experimental phenomenon. Based on the nonlinear regression analysis of the specimen parameters, the empirical expressions of the combination coefficients and design parameters are obtained. The proposed damage model can better simulate the seismic damage evolution process of piers repaired with CFRP. Five grades of RC structure damage are defined, and the damage index limit value of the five grades is given. For moderately damaged pier structures ($0.3 < D \leqslant 0.6$, D is the damage index), it is recommended to use pre-stressed CFRP reinforcement after repairing and leveling the structural surface to achieve better results.

In order to quickly and economically select the vortex-induced vibration (VIV) aerodynamic suppression measures of the open-type bluff-body bridge section, a cable-stayed bridge of the composite girder with side beam was taken as the background, and the “CFD numerical simulation selection + wind tunnel verification test” was used to study the selection of VIV aerodynamic suppression measures. The original girder section has significant VIV under frequent wind speeds. In order to complete the selection of aerodynamic measures, the CFD numerical calculation was used to simulate the flow field of the original section. Through the research on the vortex shedding state of the original section, the main vortex suppression objects were determined. Then the three aerodynamic measures (lower central stabilizer, guide vane, and wind fairing) were simulated in a targeted way to suppress the main shedding vortexes. By comparing the vortex shedding state and the three-component force coefficient of each section, the relative advantages and disadvantages of the VIV performance of each section were obtained. Finally, the combined aerodynamic measures involving the wind fairing and the lower central stabilizer were selected for the wind tunnel verification test. The test results show that the combined aerodynamic measure can effectively suppress the VIV of the girder at various wind attack angles. At the wind attack angle of +5°, the reduction effect of three combined aerodynamic measures, namely, the guide vane, the lower central stabilizer, and the wind fairing, on the VIV amplitude of the original section obtained through the wind tunnel test increases accordingly, which is 2.7%, 27.7%, and 87.4% respectively. The relative relationship between the VIV suppression capacity of three aerodynamic measures obtained through wind tunnel tests is consistent with the numerical simulation results. The numerical simulation results meet the expected requirements, and the data set for comparing the numerical simulation and wind tunnel test results can be further expanded for different bridge sections in the future, so as to select aerodynamic measures more accurately and quickly.

A feature point and line hierarchical matching method is proposed, suitable for oblique images to solve the challenges of large angle in view transformation, a few matches due to repeated texture, and low matching accuracy. Firstly, the line features of images derive from the line extraction (detection) algorithm (LineSegmentDector), follow constraints to pair, and construct line pair regions to match the improved SIFT feature descriptor. Secondly, after RANSAC algorithm eliminates mismatches, the epipolar constraint acts upon the initial matching results. Then, the obtained lines correct the local image, and the corrected local image uses SIFT matching, which contributes to calculating the original image reversely. The obtained matching points are used to globally correct the oblique image, and the feature points are matched; the grid-based motion statistics (GMS) algorithm eliminates the mismatches; the matching results go through reverse calculation and return to the original image. The line matching results and the point expanding matching results combine into final results, showing that the matching accuracy of the proposed method is close to that of ASIFT, but the number of matching is 1-3 times it.

Ensuring the long-term stability of the pile foundation in ice-rich frozen soil areas is the key to the safe use of bridge pile foundations in permafrost areas. In order to analyze the influence of ice content on the creep characteristics of the frozen sand-concrete interface, the creep tests of the frozen sand-concrete interface with ice content of 6%, 12%, 16%, 23%, 36%, 60%, and 80% were carried out under −2 ℃ by using self-designed large-scale shear apparatus. According to the test results, except for the accelerated creep of the specimen with 6% ice content, other specimens only experience decay creep and stable creep stages under constant shear stress. With the increase in ice content, the proportion of viscous deformation in the specimen increases, and the viscous deformation in the specimen with 80% ice content exceeds 80% of the total deformation. The stable creep speed is affected comprehensively by the dry density and ice content and is the lowest when the ice content is 16%. Burgers viscoelastic model can simulate the creep curve of frozen sand-concrete interface with high ice content better. With the increase in ice content, the initial shear modulus and viscosity coefficient at the stable creep stage increase first and decrease then. The progressive shear modulus at the initial creep stage decreases exponentially, and the viscosity coefficient at the initial creep stage increases exponentially.

To investigate the mechanical properties and failure characteristics of granite intersected with single fractures, uniaxial compression tests were carried out on intact granite and granite intersected with fractures at inclined angles of 30°, 45°, and 60°, which were selected from the Beishan area for geological disposal of highly radioactive waste in Gansu Province of China. The results show that as the inclined angle of the fracture increases, the uniaxial compressive strength, damage stress, and elastic modulus of the specimens decrease. Compared with intact granite, the uniaxial compressive strength of fractured granite at inclined angles of 30°, 45°, and 60° decrease by 7.97%, 29.17%, and 71.68%, respectively, while the damage stress decreases by 9.35%, 24.26%, and 69.79%, respectively. In addition, the elastic modulus of the specimens decreases by 5.89%, 23.32%, and 60.49%, respectively. The stress–strain curves of the specimens show significant differences when the inclined angles of the fractures are different. The larger inclined angle of the fractures indicates a more obvious yield stage between the damage stress and the peak stress, representing more obvious slip failure characteristics along the fracture surface. The inclined angle of the fractures influences the failure mode of granite. The failure modes of the specimens can be divided into three types: failure with fractures intersecting the fracture surface (inclined angle of 30°), slip failure along the fracture surface (inclined angle of 60°), and the compound failure of the first two forms (inclined angle of 45°). Furthermore, the compressive strength of fractured granite at a inclined angle of 60° shows a power function growth relationship with the difference in fractal dimension of the fracture surface before and after the test.

With the rapid development of transport infrastructure, the dynamic properties of soil under long-term cyclic loading and the corresponding constitutive model system are receiving increased attention, which can provide a theoretical basis and technical support for the assessment of the dynamic stability and service performance of foundations or geotechnical structures under such loading. In the past 20 years, Chinese and foreign scholars have carried out a large number of indoor experiments to explore the dynamic behaviors and influencing factors of soil under long-term cyclic loading, established corresponding theoretical models to describe the characteristics of long-term cyclic deformation of soil, and applied them to engineering practice. At present, the research on dynamic performance and the main influencing factors of soil under long-term cyclic loading is sufficient. However, how to reduce the parameters of these constitutive models and enhance their applicability in complex working conditions with variable amplitudes and frequencies needs to be further studied. Through the summary of research development, this paper clarified the development direction of this topic and proposed some possible solutions to the current research limitations, which was beneficial for applying research findings in engineering practice.

In order to explore the influence of section parameters and joint forms on the seismic performance of the straight-tenon joints with a bolt pin, four full-scale joint specimens were designed and fabricated, with beam height and beam width as the research parameters. In addition, they were compared with the through-tenon joint with a bolt pin. Then, through low-cycle reciprocating loading tests, the failure modes, hysteresis loops, skeleton curves, ductility, strength degradation, stiffness degradation, and energy dissipation capacity of the joints with different parameters were studied. Finally, the theoretical formula of bending moment versus angle of the straight-tenon joints with a bolt pin was derived and compared with the experimental results. The study results show that the primary failure modes of the specimens are the tension failure along the tension edge of the beam tenon inside of the column, accompanied by the extrusion deformation of the compression edge of the beam tenon inside of the column and the horizontal splitting of the beam tenon outside of the column. The hysteretic loop of bending moment versus angle of the joints shows an anti-Z shape with an obvious pinching effect. Within the range of experimental design parameters, with the increase in beam section height and beam section width, the rotational stiffness and flexural bearing capacity of the straight-tenon joints with a bolt pin increase, but the changes of strength degradation coefficient and equivalent viscous damping coefficient are not obvious. Compared with the through-tenon joint with a bolt pin, the flexural bearing capacity of the straight-tenon joint with a bolt pin is 62% larger in the downward loading direction and is 26% larger in the upward loading direction, and the bearing capacity decreases more slowly in the post-peak stage. It reflects that the straight-tenon joint with a bolt pin has better seismic performance than the through-tenon joint with a bolt pin. The error between the test and the theoretical formula of the straight-tenon joints with a bolt pin is within 9%.

In order to reduce the deflection amplitude of the continuous rigid frame bridge span, an optimized control method of mix proportion based on the dense packing theory of aggregates was proposed for the two influencing factors of elastic modulus and creep. In addition, the original mix proportion was studied to analyze the influence of the optimized control method on the elastic modulus and creep under different ages and environments. At the same time, the optimization mechanism was analyzed from the microscopic level of concrete in combination with scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) experiments. Based on the CEB-FIP (1990) model, a modified model considering the maturity of elastic modulus was proposed. The results show that the optimized control method can effectively control the elastic modulus of concrete at an early age, but the increase in the area of the interface transition zone limits the later development of the elastic modulus. Under the same conditions, the creep coefficient of the optimized concrete is reduced by 12%–23% compared with the original mix proportion. Moreover, the influence of the environment on the concrete creep is dominant compared with the optimized control method. The variation range of concrete creep under different environments is between 45% and 60%. Concrete creep decreases with the loading age, and the creep of optimized concrete at a small loading age is still 3%–13% lower than the original mix proportion of the concrete at a large loading age. After optimization, the number of internal pores and micro-cracks in the concrete at an early age is reduced. Therefore, the internal structure of the concrete is improved. The modified CEB-FIP (1990) model has higher accuracy in predicting creep.

In order to study the dynamic response characteristics of the pulse wind tunnel balance foundation under the action of pulse aerodynamic loads, a pulse wind tunnel was taken as an example, and a typical aerodynamic load action type was selected. As a result, a simplified calculation method for dynamic characteristics of the pulse wind tunnel balance foundation such as displacement of the vertical direction, displacement of the horizontal direction, and rotation angle was established, and its reliability was verified by numerical simulation. The results show that under the action of a typical aerodynamic load, the balance foundation has a maximum vertical vibration amplitude of 0.001 75 mm and a frequency of 7.94 Hz; a maximum horizontal vibration amplitude of 0.002 83 mm and a frequency of 7.94 Hz; a maximum amplitude of the rotation angle of 0.000 34° and a frequency of 7.94 Hz. The typical aerodynamic load has little effect on the vibration of the balance foundation, and no resonance phenomenon occurs. Meanwhile, the maximum amplitude of foundation vibration increases with the increase in aerodynamic load, and the frequency of foundation vibration increases with the increase in aerodynamic load frequency; under the condition of constant aerodynamic load, the maximum amplitude and frequency of foundation vibration gradually decrease with the increase in size; the maximum amplitude of the foundation vibration decreases with the increase in foundation soil properties, but the change of foundation soil properties has no effect on the foundation vibration frequency.

In order to analyze the cascading failure of the transmission tower–line system under strong wind, this paper took the collapsed transmission tower as the weak tower and used equivalent displacement to consider the influence of weak tower collapse on the spatial location of suspension points. The responses and failure characteristics of the adjacent transmission tower (target tower) under multiple combined groups of the weak tower collapse parameters were calculated, and the weak tower collapse parameters with the greatest influence on the target tower were determined. The results show that when cascading failure happens, the failure of the target tower includes two types, the failure of the tower body near the weak tower and the failure of the tower head. The main bracing on the leeward side of the weak tower has the highest stress ratio. The stress ratios of diagonal bracings are always low. The most direct causes of the overall collapse of the target tower are the instability of diagonal bracings at the lower part of the target tower and the continuous increase in stress of the main bracing. The duration of the weak tower collapse is the main control variable for the failure of the target tower.

To solve the problem that the scale factor error and installation error of odometers have a great influence on the accuracy of strapdown inertial navigation/odometer integrated navigation, a fast calibration method based on short-term SINS (strapdown inertial navigation system) information is proposed for odometer parameters. By establishing a dead-reckoning error model, the relationship between the output speed of the inertial navigation system and the output of the odometer in the inertial measurement unit (IMU) coordinate system is constructed, and the formula of calculating the odometer parameters is obtained. The least squares method is utilized to calibrate the odometer scale factor and installation error. This method only uses strap-down inertial navigation information to achieve the initial calibration of the odometer parameters within 1 min. It does not require the assumption that the error value of the relevant parameters is small, and ignores the influence of the lever arm effect on the calibration effect. The test results show that, when the vehicle has been running for 30 min, the accuracy of the horizontal dead-reckoning method calibrated by this method is 92.3% higher than that of the traditional calibration method.

To mitigate the impact of large-scale integration of distributed generation (DG) on the secure and stable operation of distribution networks, we propose an active distribution network optimal reconfiguration method that considers the uncertainty of distributed power generation output, based on non-cooperative game theory. Firstly, non-cooperative game theory is employed to analyze the game relationship between the distribution network topology and DG output, considering the uncertainty of photovoltaic units in the distribution network system as a player. Secondly, an optimal reconfiguration model with the objective functions of minimizing active network loss, balancing load and minimizing voltage deviation is established. The model is solved iteratively using the backtracking search algorithm (BSA) to obtain the optimal reconfiguration solution. Finally, simulation analysis is conducted using the IEEE33-node system to verify the correctness of the proposed model and the effectiveness of the algorithm. The results indicate that, compared to traditional reconfiguration methods, the proposed optimal reconfiguration approach in this study comprehensively addresses the uncertainty of distributed power generation output. In the most adverse scenario, the reconfiguration strategy can lead to a reduction of 0.31%, 0.59%, and 0.48% in active power loss, load balancing, and voltage deviation indices within the distribution network system.

Following the guideline of the reasonable planning and sustainable development of photovoltaic (PV) power plants, an emergy analysis based method is proposed for the site selection and eco-economic benefit assessment of PV power plants. Through the combination of emergy analysis and geographic information system (GIS) spatial analysis, the eco-economic benefits of land available for PV generation in 12 league cities of Inner Mongolia China are analyzed. The result shows that: Hohhot, Baotou and other densely populated areas in central and western Inner Mongolia show more excellent development value. Through comparison, it is found that the transmission loss caused by transmission distance accounts for a decisive proportion of all emergy inputs. In addition, for most of available land plots, the eco-economic benefits are relatively higher when they are close to urban towns or built environment. In the process of structural transformation of energy, the occupation of PV land and the expanding demand for urban construction land may become the primary imbalance between urban planning and PV energy planning in the future.

The decomposition of top-level design indicators is the primary link to determine the cycle length and success of forward design for high-speed trains. First, on the basis of expounding on the top-level design indicators of high-speed trains in terms of transportation capacity, safety and comfort, environmental protection, and economy, the decomposition challenges of top-level design indicators for high-speed trains were proposed from the perspectives of system structure, operating boundary conditions, and large-scale system coupling. Then, the research status was discussed, including the decomposition method, decomposition association model, and decomposition coordination strategy of design indicators, and the deficiencies and new needs of the existing methods were analyzed. Finally, the applicability of community ecology in the decomposition of top-level design indicators for high-speed trains was prospected. In addition, the key problems that will be faced by the decomposition of top-level design indicators for high-speed trains based on community ecology were analyzed, and corresponding technical routes for solutions were given, so as to provide a reference for the in-depth research and practice of the decomposition of top-level design indicators for high-speed trains.

In view of engine knock, a technical solution was proposed to achieve a natural gas engine with a high exhaust gas recirculation (EGR) rate by utilizing a zero-power consumption ejector. Firstly, the structural parameters of the ejector were designed and calculated under specified operating conditions. Subsequently, the ejector simulation model was established, and the model was verified using experimental data. Furthermore, the ejection performance variations of the ejector with structural parameters were analyzed, and the influence of structural parameters on ejection performance was obtained. Lastly, a novel sensitivity evaluation index for structural parameters was introduced to examine the extent of their influence on ejection performance. The results show that as the length of the mixing section and the diffuser section increase, the entrainment coefficient (μ) increases. Conversely, as the diameter of the mixing section (d₃), the angle of the diffuser section (θ_s), and the distance from the nozzle outlet to the mixing section (L_NXP) increase, μ increases first and then decreases. The maximum value of μ is observed at d₃ = 46.1 mm, θ_s = 4°, and L_NXP = 57.33 mm, respectively. Among the structural parameters, d₃ exhibits the most significant influence on μ, with a corresponding sensitivity index of 0.88. However, L_NXP had the least impact on μ, with a sensitivity index of 0.05.

Inspired by the fact that a human torso has both rigid skeletons and flexible internal organs, a passive walking robot model with a rigid and flexible bionic torso was proposed to improve the gait property of the robot, and the nonlinear dynamic properties of the robot were studied. First, the dynamic equations of the passive walking robot with a bionic torso were established by considering the flexible part of the torso as a mass-spring-dashpot system. Then, the effects of the equivalent elasticity coefficient, damping coefficient, and mass of the bionic torso on walking step length and walking speed of the robot were investigated respectively. The results show that compared with the rigid torso, the bionic torso enables a more abundant gait behavior for a passive walking robot. The flexibility of the bionic torso affects the walking step length, walking speed, and walking stability of a passive walking robot. With appropriate torso flexibility, the walking step length and walking speed of the robot can be improved while the stable periodic gait remains. Compared with the rigid torso, the walking step length and walking speed of the robot with a bionic torso can be increased by 12% and 2%, respectively.