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.

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.

In order to explore the influence mechanism of arch bridge deformation on the running stability of the train under crosswind, the horizontal and vertical displacement of the mid-span was obtained through the wind, vehicle, and bridge coupling system, and the running stability of the train under different wind speeds and train speeds was analyzed. The contribution of bridge deformation to horizontal and vertical acceleration of the train in the wind, vehicle, and bridge system was quantified. Combined with the sensitive wavelength of the acceleration response of the train and the time-frequency characteristic of bridge deformation, the influence mechanism of bridge deformation on running stability was analyzed. The results show that the vertical displacement difference of the bridge is smaller than the horizontal displacement difference, and the main displacement is caused by the vehicle-induced bridge deformation. The maximum value reaches −9.2 mm. Under the action of train and wind load, the horizontal and vertical displacement of the bridge is more significant, but its influence on the stability of the train is mainly reflected in the position of the junction pier, which is about four times the response of other positions. Except for the junction pier area, the running stability of the train on the bridge is mainly determined by the wind-induced train vibration and track irregularity. The spectral density distribution of horizontal and vertical acceleration power of the train is closely related to the wavelength of track irregularity, and the corresponding sensitive wavelength range is less than 120 m. The horizontal and vertical acceleration of the train is mainly affected by the bridge deformation caused by the vehicle load, while the bridge deformation caused by wind load is mainly distributed in the main span, and the wavelength is larger than 120 m. Therefore, it does not exert a significant impact on the acceleration of the train.

The stay cable is one of the main load-bearing elements of cable-stayed bridges, and the disease of its outer sheath is easy to penetrate inside the cable and affect the health of the steel wire. Therefore, it is significant to use the video image method to intelligently identify the apparent disease of the cable. Based on image recognition, the methods of apparent disease recognition for stay cable were systematically reviewed from two aspects: traditional image detection and deep learning. The basic principles and application effects of each method were introduced, and the current detection examples were analyzed. Some cutting-edge deep learning methods were introduced to provide a reference for the apparent detection of cables. The main features of various methods were summarized, and the problems existing in the current detection were discussed and prospected. The deep learning model-based image recognition method had better recognition accuracy and algorithm robustness, stronger learning ability and adaptability, and optimal comprehensive image defect recognition effect, but there were still difficulties such as the difficult balance between detection accuracy and speed, large image data demand, and high labeling cost. To this end, detection methods could be improved by improving image quality, constructing more semi-supervised and unsupervised deep learning models, and enhancing the learning ability of detection models.

In order to master the constraint effect of new high-strength steel wire cloth reinforced ultra-high performance concrete (UHPC), a study was conducted on the influence of the surface density and number of layers of high-strength steel wire cloth on the axial compression performance of confined concrete columns. Firstly, the constraint effect of high-strength steel wire cloth reinforced UHPC was evaluated using Poisson’s ratio, ductility index, and toughness index. Secondly, a lateral constraining force model of the composite constraining layer was established considering the constraining force provided by high-strength steel wire cloth and UHPC. Finally, a constitutive model of axial compression of confined concrete was established based on the Ottosen failure criterion and an effective constraint index. The results show that the confined column exhibits obvious ductile failure under compression, and the high-strength steel wire cloth reinforced UHPC confinement system can effectively suppress crack development and slow down the stiffness degradation of the specimen in the later stage of loading. Compared with the unconfined column, confined columns have maximum increases of 147.0%, 104.0%, and 58.0% in ultimate bearing capacity, peak compressive strain, and peak stress, respectively. When the number of layers of high-strength steel wire cloth increases from 1 to 2, and the surface density increases to 3.3 times, the ultimate bearing capacity, peak compressive strain, and peak stress of the confined column increase by 8.4%, 29.3%, and 15.8%, respectively, while the ductility index and toughness index increase by 50.3% and 44.2%, respectively. The model established in this paper highly agrees with the experimental results compared with the classical constitutive model of axial compression of confined concrete.

In order to study the shear behavior of studs embedded in engineered cementitious composites (ECC), model tests and the numerical analysis of finite elements were carried out. The failure mode of studs embedded in ECC was determined based on push-out model tests. Then, parametric numerical analysis of finite element was performed to elucidate the effects of stud diameter, height/diameter ratio of stud, tensile strength of stud, and compressive strength of ECC on the shear behavior and failure mode of connectors. Finally, a method for calculating the shear capacity of studs embedded in ECC was established according to the above research. The results show that the shear strength of studs embedded in ECC is closely related to the failure mode of the push-out model. When the push-out model fails due to ECC crushing, the shear strength of the connector depends on the compressive properties of ECC. When the push-out model fails due to stud fracture, the shear strength of the connector depends on the tensile strength of the stud and compressive properties of ECC; increasing the compressive strength of ECC and reducing the height/diameter ratio of the stud both can improve the shear stiffness of the connector, but the tensile strength of the stud has a slight effect on the shear stiffness of the connector. When the height/diameter ratio of the stud is lower than 4.60, the shear strength of the stud reduces with the decreasing height/diameter ratio of the stud. Studs with a height/diameter ratio of greater than 4.60 are recommended to serve as a shear connector applied in steel-ECC bridge decks.

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 study the bearing capacity of energy piles in sand affected by thermal-cool cycles, a centrifuge model test on slender energy piles buried in Fengpu sand with different compactions was carried out. The change rules of the axial force, side friction, and individual bearing capacity of energy piles were obtained and compared under 20 thermal-cool cycles in the test. The test results show that the axial force of the energy pile decays gradually and tends to be stable with increasing thermal-cool cycles. The maximum axial force attenuation value of the energy pile buried in the sand with medium compaction is much larger than that buried in the dense sand. During thermal-cool cycles, for energy piles buried in the sand with medium compaction, a neutral point is located at the bottom half of the pile. Positive additional side friction is generated above the neutral point during cool cycles, and negative additional side friction is generated underneath the neutral point. Oppositely, during thermal cycles, negative additional side friction appears above the neutral point, and positive additional side friction is underneath the neutral point. The dense sand has an obvious constraint effect on the lower part of energy piles. Positive additional side friction is distributed along the pile during cool cycles because the pile moves downward relative to the surrounding soil. During thermal cycles, the additional side friction is negative. The bearing capacity of the energy piles will be reduced because of the long-term temperature cycles. The bearing capacity of the energy piles buried in the dense sand and sand with medium compaction is reduced by 7.3% and 15.6%, compared with the prototype pile. The bearing capacity of the prototype pile and energy piles buried in the dense sand is 11% larger than that of the prototype pile buried in the sand with medium compaction. Therefore, reasonable measures should be taken to meet the bearing requirements of energy piles when buried in sandy layers with different compactions in actual engineering.

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 3.4 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.

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.

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.

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.

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.

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.

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.

This paper aims to study the effect of spanwise variation of vibration amplitude and spanwise correlation of the nonlinear aerodynamic forces on the vortex-induced vibration (VIV) response of bridges. Firstly, a nonlinear aerodynamic force model of the bridge represented by polynomial functions of vibration amplitude was introduced. Secondly, on the basis of the two-dimensional VIV (2D VIV) analysis method, an approach for predicting the three-dimensional VIV (3D VIV) amplitude response with consideration of both spanwise variation of vibration amplitude and spanwise correlation of aerodynamic forces was proposed through theoretical analysis. Finally, by taking a 1 700 m long-span suspension bridge as an example, the nonlinear aerodynamic force parameters of vertical VIV of the bridge girder at different angles of wind attack were extracted through a wind tunnel test. Then, the VIV amplitude response of the suspension bridge under a first-order positive symmetrical vertical mode at different angles of wind attack was analyzed. The results prove that when the aerodynamic forces are assumed to be fully correlated along the span, the 3D analysis under different wind speeds leads to a significantly higher VIV amplitude response (about 19%) as compared with the 2D analysis method due to the effect of spanwise variation of vibration amplitude of the aerodynamic forces. However, when the aerodynamic forces are assumed to be partially correlated along the span, the VIV amplitude response by 3D analysis is reduced significantly, and the reduction range is about 16%–30% under most wind speeds and about 70% under certain wind speeds. It is proved that it is important to accurately predict the VIV amplitude response of long-span bridges by considering the spanwise variation of vibration amplitude and spanwise partial correlation of aerodynamic forces. The approach proposed in this paper is also applicable to the analysis of torsional VIV or VIV at higher-order modes.

In order to analyze the feasibility of a dual-source-powered electric multiple unit (EMU) with enhanced operational efficiency on the Qinghai–Xizang Line (Golmud–Lhasa section), the dynamics model of EMU was established and verified. A dynamic method was adopted to study the relationship among the traction adhesion coefficients, traction force, creepage, and speed for the dual-source-powered EMU and the HXN₃ internal combustion locomotive operating on the straight sections, curved sections, and ramps of the Qinghai–Xizang Line. The adhesion characteristics of dual-source-powered EMU under traction conditions were validated by comparing the dynamic responses of the two locomotives. The analysis finds that: 1) The traction adhesion coefficients of the locomotives are proportional to their traction force. Moreover, within the speed range of 40–120 km/h, the adhesion coefficient of the dual-source-powered EMU decreases from 0.19 to 0.09, while the adhesion affluence increases from 59% to 85.7%. 2) The adhesion affluence of the dual-source-powered EMU is superior to that of the HXN₃ locomotive in both straight sections and ramps, thereby enhancing its ability to cope with low wheel-rail adhesion conditions in harsh external environments and exhibiting better adaptability in plateau environments. 3) In the curved section, by ignoring the structure-induced adhesion reduction difference, the adhesion reduction amplitudes of the dual-source-powered EMU and HXN₃ locomotive are 6.3% and 6.8%, respectively, at R300 m curve. At the R800 m curve, the HXN₃ locomotive demonstrates an adhesion reduction amplitude of 3.0%, while the adhesion reduction amplitude of the dual-source-powered EMU is below the threshold value, ensuring sufficient adhesion.

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.

As typical rail damage of the railway, rail corrugation is often accompanied by the fastener clip fracture, which seriously affects the operation safety of the train. Moreover, the small-radius section of the Cologne-egg fastener experiences frequent rail corrugation. To explre the fracture mechanism of Cologne-egg fastener clips, firstly, the finite element model of the wheel set-rail-fastener system, including the complete Cologne-egg fastener model, was established baesd on the field investigation. Then, the resonant response of the Cologne-egg fastener clip was explored, considering the frictional coupling vibration of the wheel-rail system. Finally, the fatigue life of the Cologne-egg fastener clip was compared in the cases of with and without rail corrugation sections, and the fatigue damage of different clips was quantified. The results show that the dominant frequency of the frictional coupling vibration of the wheel-rail system is consistent with the first-mode constraint mode of the Cologne-egg fastener clip in the frequent rail corrugation sections, which indicates that the clip resonance induced by the frictional coupling vibration of the wheel-rail system is the main reason for the Cologne-egg fastener fracture. The frictional coupling vibration of the wheel-rail system is aggravated by the rail corrugation, which makes the clip life of the Cologne-egg fastener in the rail corrugation section decrease by 99.04% compared with that in the absence of rail corrugation section. The clip life is thus only 3.11% of the design clip life. Besides, the Cologne-egg fastener clip on the low gauge side is more prone to fatigue failure in the small-radius curved section, and the failure position is located on the inner side of the rear arch end of the clip.

To investigate the effect of synergistic longitudinal ventilation and air curtain on the control of tunnel fire smoke in urban bifurcated tunnels, the 1∶10 small-sized bifurcated tunnel fire experiments were conducted, and the along-travel and maximum temperatures of bifurcated tunnels under the synergistic effect of longitudinal ventilation and air curtains were analyzed by taking into account the variables of longitudinal ventilation, jet velocity, angle, and thickness of air curtain. Firstly, the smoke and heat insulation effect of the air curtain was analyzed through 57 sets of small-sized tunnel fire experiments. Then, based on the dimensionless empirical correlation formula for the maximum temperature rise of the ceiling in a tunnel fire, a model of the maximum temperature rise under the synergistic effect of air curtain and longitudinal ventilation was constructed at a fixed heat release rate of 47.9 kW. Finally, the experimental values of the maximum temperature rise under different working conditions were compared with the predicted values of the theoretical models of the maximum temperature rise. The results show that an air curtain can effectively help longitudinal ventilation reduce the temperature in the main tunnel by up to 420 ℃ while effectively preventing smoke from entering the bifurcated tunnels. When the jet velocity of the air curtain is small, the increase in longitudinal wind speed can effectively prevent the accumulation of smoke in the bifurcation and improve the insulation efficiency of the air curtain on the smoke. In addition, the temperature of the smoke at the tunnel bifurcation point can be reduced by up to 170 ℃. The constructed theoretical model of the maximum temperature rise is compared with the experimental results, and the error between them is less than 10%.

New continuous cable traction power supply system (CCTPSS) can achieve long-distance transmission and reduce the number of electric phases. However, the two-stage power supply mode leads to the complex structure of the system. In order to reveal the short-circuit characteristics of CCTPSS, the two-port network parameters of traction cable and catenary-rail of unit length were established. Each sub-network was cascaded and equated with a two-port network, which was then transformed into a Ⅱ-type circuit for modeling the distribution parameters of the traction cable and catenary-rail of any length. The locomotive voltage drops after short circuit of catenary. Therefore, considering the coupling relationship between the train and the network, the short-circuit current and voltage were solved by iterative calculation. The accuracy of the calculation method was validated by simulation. Finally, the electrical characteristics of different short-circuit types were analyzed, with emphasis placed on the influence of distributed capacitance on short-circuit current and voltage. The results show that the distributed capacitance can increase the short-circuit current and, under different short-circuit conditions, the output voltage of traction transformer. The short-circuit current of catenary is jointly provided by traction transformers on both sides, and the farther away from the short-circuit point is, the less current is provided. The cable phase-to-phase short circuit has the greatest impact on the operation of the non-fault-circuit locomotive.

To reveal the variation law of dynamic response of maglev guideways, maglev trains were simplified as moving uniform loads, and analytical methods were employed to obtain the analytical solutions for dynamic response of simply supported guideways. The variation laws of the maximum response of guideways with train speed and guideway span were discussed, and the extremum conditions of response of maglev guideways were derived, which were verified by finite element and train-bridge coupling vibration methods. The results show that under the condition of a large train-guideway span ratio, the maximum response of midspan increases with fluctuations as the train speed increases and has extremums. Guideway response also has similar change laws with the variations of guideway span, mass, and other parameters. When the product of span and speed is a specific constant, or the product of the first-order vertical frequency and span of guideway is a specific time the train speed, the guideway produces vibration isolation.

Establishing a reasonable and accurate theoretical analysis model for pipe sheds and solving it are of great significance to promoting the development of pipe shed pre-support technology. By analyzing the construction process of tunnel excavation and support and the reduction of the restraining reaction force of the pipe shed due to the disturbance of the tunnel face in the unexcavated section, a load structure model of the pipe shed based on the Euler-Bernoulli beam theory was established. The Pasternak elastic foundation model was introduced to determine the initial support and the restraining reaction force of the rock mass in front of the tunnel face on the pipe shed, and the analytical expressions of the stress and deformation of the pipe shed during each cycle of tunnel excavation and support were derived. In addition, the superposition method was used to solve the stress and deformation distribution of the pipe shed when the tunnel face was tunneled to any position. Through case comparison, the rationality and effectiveness of the model were verified. The research results show that smaller circumferential spacing and larger diameter of the pipe shed steel pipes are helpful in improving the pre-reinforcement capacity of the pipe shed, and the reasonable lap length of the pipe shed is 1.8 m.

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.

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.

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 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.

The traditional prediction model for the civil engineering cost of urban rail transit lacks decision-making credibility. To address this issue, First, critical factors affecting the civil engineering cost of urban rail transit were retrieved utilizing the feature selection and knowledge judgment methods, and an engineering case database was created. Then, similar cases were screened using the particle swarm optimization (PSO) clustering algorithm, and a nonlinear prediction model of civil engineering cost was established using the extreme learning machine (ELM) based on gray wolf optimizer (GWO), followed by a dual environment comparison experiment. Finally, Sobol’s global sensitivity analysis and curve fitting analysis were conducted to invert the model and validate its superiority by using the Chengdu Rail Transit Line 10 Phase 1 Project as an example. The results show that the prediction model’s mean absolute error and root mean square error are 0.113 9 and 0.127 4, respectively, and the mean absolute percentage error is 4.14%. The prediction effect of the nonlinear cost prediction model is better than that of the linear model, and the better prediction effect is obtained by simultaneously using the factor optimization and case clustering methods. The global sensitivity study reveals that the total sensitivity of the subterranean line length and the number of underground stations is much larger than the other factors, making them the major factors to be adjusted for the scheme optimization. The “black box” effect of intelligent predictive modeling mechanism based on machine learning is better understood by 33.70%–64.52% when curve fitting analysis is used.

To investigate the effect of freeze-thaw cycles and coupling of freeze-thaw cycles and bending loads on the flexural performance of polypropylene fiber cement-based composite (PP-ECC) beams, seven experimental working conditions were set up. In addition, the three-point loading method was adopted to explore the flexural performance of PP-ECC beams. The differences in load-span deflection curves, flexural bearing capacity, and crack development patterns of PP-ECC beams under coupling of freeze-thaw cycles and bending loads were analyzed. Based on the calculation assumptions and the calculation model of the flexural bearing capacity of PP-ECC beams under normal environments, combined with the freeze-thaw deterioration mechanism of PP-ECC materials, the calculation model of flexural bearing capacity of PP-ECC beams under freeze-thaw environments was deduced. Furthermore, the load-bearing damage coefficient γ was introduced on this basis. The calculation model of the flexural bearing capacity of PP-ECC beams under the coupling of freeze-thaw cycles and bending loads was established. The research results show that the ultimate flexural bearing capacity of PP-ECC beams with different load-bearing ratios decreases to varying degrees under freeze-thaw cycles. After 500 freeze-thaw cycles, the ultimate flexural bearing capacity of PP-ECC beams with load-bearing ratios of 0, 0.25, and 0.5 decreases by 28.70%, 27.09%, and 35.69%, respectively. After cracking under tension, the PE-ECC material can still work with the rebar under tension and participate in the stress of the whole section. When the PP-ECC beam reaches the limit state, the zone under tension develops steadily with multiple cracks. With the aggravation of freeze-thaw damage, the width of the largest crack in the beam body increases, and the number of cracks decreases. The PP-ECC beam subjected to freeze-thaw cycles and coupling of freeze-thaw cycles and bending loads still satisfies the plane section assumption. The coincidence degree of the flexural bearing capacity calculation models of PP-ECC beams under freeze-thaw cycles and coupling of freeze-thaw cycles and bending loads established based on the plane section assumption reaches 0.88–1.06 and 0.96–1.10, respectively.

To investigate the seismic performance of concrete composite columns of ultra-high performance concrete (UHPC) precast pipe under low-cycle repeated loads, three concrete composite columns of UHPC precast pipes and one reinforced concrete (RC) column were subjected to quasi-static tests, so as to analyze the seismic performance of each composite column specimen in terms of damage mode, displacement ductility, energy dissipation capacity, and stiffness degradation under different UHPC strengths and core concrete with or without reinforcement. The analysis results show that the hysteresis curves of the concrete composite column specimens of UHPC precast pipe are fuller, and their damage patterns are basically the same, which are both integral compression-bending damage. Compared with those of the conventional RC columns, the stiffness, yield load, and ductility of the concrete composite column of UHPC precast pipe are improved. With the increase in UHPC strength, the hysteresis curves of the composite column specimens are fuller, and the energy dissipation capacity is enhanced. The residual displacement is small, and the horizontal peak load and displacement ductility coefficient increase by 20.6% and 6.4%, which shows good overall seismic performance. The finite element analysis model of the composite column is established by the ABAQUS program, and the calculation results are in good agreement with the test results. Different axial compression ratios, slenderness ratios, and UHPC strengths are important parameters affecting the seismic performance of concrete composite columns of UHPC precast pipes, which can provide a reference for similar engineering designs.

With the explosive development of electric vehicles (EV), the contradiction between the impact of charging load and grid support capacity is highlighted. In response to this problem, an EV charging and discharging (vehicle to grid, V2G) optimization strategy was proposed from the perspective of the game between supply and demand. Firstly, a power price sharing mechanism was constructed to make EV charging and discharging mutually appropriate with base load by combining the characteristics of EV charging and discharging behaviors. Then, for the leader-follower game relationship between the aggregator’s pricing of electricity and the EV users’ charging and discharging behavior selection process, an optimization model was established, whose optimization objectives are maximizing the revenue of the aggregator on the leader level and minimizing the cost of electricity for EV users on the follower level. Finally, the seeker optimization algorithm was used to solve the optimization objectives of both sides separately, and the game cycle was carried out until the equilibrium, so that the optimal electricity pricing strategy and EV charging/discharging strategy were obtained. The simulation results show that the proposed charging and discharging strategy can realize the peak-cutting and valley-filling of the base load curve by the EV charging and discharging load. The variance of the base load curve is reduced by 56.6%, and the difference between peak and valley is decreased by 28.0%. Meanwhile, the charging and discharging cost of EV users is lowered by 40.4%, and the revenue of the aggregator is increased by 40.1%.

To study the buckling performance and bearing capacity design method of the cold-formed thin-walled steel (CFTWS) with unequal-leg lipped angles under axial compression, the tests were conducted, and a finite element program was used to analyze the buckling performance and ultimate bearing capacity. Based on the direct strength method, the bearing capacity design method was presented. Firstly, the 32 CFTWS with unequal-leg lipped angles with different sections, slenderness ratios, and width-to-thickness ratios were tested under axial compression. Then, ABAQUS finite element software was used to perform parametric analysis on the buckling performance and bearing capacity of CFTWS with unequal-leg lipped angles with different width-to-thickness ratios, width ratios of legs, and slenderness ratios. Finally, the modified direct strength method for calculating the bearing capacity of CFTWS with unequal-leg lipped angles under axial compression was proposed based on the results of the test and finite element analysis. The results show that the specimens with a small width-to-thickness ratio are prone to flexural-torsional buckling, while the specimens with a large width-to-thickness ratio are prone to the local buckling or buckling related to flexural-torsional buckling and local buckling. The ultimate bearing capacity of the specimens decreases with the increase in the slenderness ratio, and the increase amplitude of the bearing capacity slows down with the increase in the width-to-thickness ratio. The reliability analysis shows that the reliability indexes of the bearing capacity of the CFTWS with unequal-leg lipped angles under axial compression calculated using the modified direct strength method are greater than 3.2, indicating that the proposed method is accurate and reliable.

In digital twin technology, the operation of complex models and production logic consumes a large number of resources. Meanwhile, differences in hardware capabilities and user requirements make it difficult to ensure simulation accuracy and real-time performance, reducing system availability. To address this issue, a real-time synchronous computing framework for digital twin manufacturing equipment that collaboratively processed visualization and logic computation was proposed. Firstly, a digital model of the equipment was constructed based on multidimensional workshop information. According to hardware capabilities and users’ personalized computational needs, a configurable and adaptive system environment mapping method was introduced to adjust simulation fidelity, ensuring the real-time and correct operation of the twin equipment. The process was illustrated by using lighting environment mapping as an example. Secondly, a simulation-based motion logic solving algorithm for a six-degree-of-freedom (6-DOF) manipulator was presented, which used the rendering frame time as the simulation clock advancement step to ensure accurate model motion and synchronization between visualization and computation. The algorithm was generalized for application to other multi-body equipment. Finally, a web-based digital twin workshop modeling and simulation cloud platform was designed and developed. A 6-DOF manipulator and a specific bogie frame processing workshop were used as application cases, and the proposed method was validated. The results show that with the adaptive reduction of mapping fidelity, simulation response speed is increased by 45%, while GPU and CPU resource utilization is effectively reduced. It proves that the method can achieve reasonable resource allocation and efficient system computation while reducing error accumulation, making it a highly available real-time collaborative computing method.

In order to accurately grasp the main parameters and diffusion and propagation laws inherent in urban traffic congestion sources and realize scientific control of traffic congestion sources, the Gaussian plume model for air pollutant dispersion was introduced and improved. The urban traffic congestion sources were divided into continuous traffic flow and a series of intermittent traffic flow, so as to realize the structural analysis of the Gaussian plume model. Then, three test functions, namely Griewank, Schaffer, and Rastrigin were used to test the “single point source” parameter inversion algorithm, and the seeker optimization algorithm was selected. Finally, the performance of the five typical objective functions with different numbers of parameters (one, two, and three) was evaluated in three dimensions based on the observed traffic congestion source data. The results show that in the one-parameter case, the stability of the objective function based on the sum of squared deviations of traffic density per unit area is better, and the confidence interval of the absolute value of the relative deviation of the inverse source strength is 38.38% ± 9.94%; the number of experiments less than 50% accounts for 84.52% of all experiments, and the stability of each objective function is better. In the two-parameter case of source strength inversion, the accuracy of the objective function based on the root-mean-square error of traffic density per unit area in the form of logarithmic transformation is the highest, and the confidence interval of the absolute value of the relative deviation of source strength inversion is 51.42% ± 9.84%; the number of experiments less than 50% accounts for 92.16% of all experiments. In terms of inversion location, the accuracy of the objective function based on the sum of squared deviations of traffic density per unit area is the best (The absolute value of position deviation inversion is 37.22 m ± 10.64 m), and the stability of the objective function based on correlation coefficient is the strongest (coefficient of variation is 0.022). In the three-parameter case, the accuracy inversion results are more consistent with those in the two-parameter case, and the source strength stability of each objective function is poor except for the objective function in the form of logarithmic transformation, but the position stability is better.

In order to deeply study the protective effect of geogrid-reinforced buried pipelines under vertical load, indoor model tests were carried out, and a discrete element simulation analysis model was established. The mechanical response and deformation behavior of geogrid-reinforced buried pipelines and surrounding soil systems under vertical load were explored from the mesoscopic level, and the development and evolution laws of the load-settlement curve of loading plate, contact force between particles inside the model, particle displacement, and vertical radial deformation of pipelines were revealed under different buried depths of pipelines and reinforcements. The results show that when the buried depth of the pipeline is shallow (H = 1.5D), the ultimate bearing capacity is smaller than that of the pipeline with a large buried depth. Although the settlement of the loading plate is smaller under the same load, the vertical radial deformation of the pipeline is large. After the geogrid above the pipeline is reinforced, the ultimate bearing capacity of the model system is significantly increased, and the vertical radial deformation of the pipeline is reduced. A shallower buried depth of the geogrid indicates a more obvious reinforcement effect. When the buried depth of the geogrid u is reduced from 0.75B to 0.25B, the ultimate bearing capacity is increased by about 57.2%, and the radial deformation of the pipeline is reduced by about 27.9%. In this study, the interaction mechanism among pipelines, soil, and geogrid is revealed from the mesoscopic level, and the mechanical and deformation behavior of geogrid-reinforced protected buried pipelines were visualized.

Accurate identification of key nodes is of great significance for enhancing network resilience and improving operational capabilities. In order to improve the identification accuracy of key nodes in the en-route network, a comprehensive evaluation method based on the technique for order preference by similarity to an ideal solution (TOPSIS)-grey correlation analysis method and a node classification method for the en-route network were proposed. Firstly, an evaluation index system of key nodes in the en-route network was constructed from three perspectives: complex network characteristics, traffic volume, and vulnerability. Then, the relative entropy was introduced to improve the TOPSIS method, and the importance of en-route waypoints was comprehensively evaluated by combining this method with the grey correlation analysis method. The K-means clustering method was used to effectively divide the levels of en-route waypoints. Finally, key node identification was carried out based on the actual operation data of civil air traffic management. It finds that the results obtained by the constructed evaluation index system of key nodes in the en-route network are more comprehensive than the evaluation results of a single index. The improved TOPSIS-grey correlation analysis is more accurate than the traditional TOPSIS method. The proposed identification method finds that there are 29 key nodes in the typical busy en-route network in Eastern China, which play a key role in the network structure and traffic volume.

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 ≤ 0.1 μm), PT-Ⅰ (r∈[0–0.1) μm) of pore throat, fractal dimension of pore (D_P), and fractal dimension of pore throat (D_PT) decrease exponentially. While, the mesopores (r∈[0.1–1) μm), macropores (r ≥ 1 μm), PT-Ⅱ(r∈(0.1–4] 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.

In order to design an efficient and robust evolution algorithm, the fixed point iteration idea in solving equations was first introduced into the optimization field. The optimization process of an evolution algorithm was regarded as the gradual display process of the fixed point of an equation in an iterative framework. On this basis, a novel evolution algorithm based on a mathematical model was developed, named fixed point evolution algorithm (FPEA). The reproduction operator of FPEA is a quadratic polynomial which is derived from a fixed point iteration model with the Aitken method. The overall framework of FPEA inherits the population-based iterative model of traditional evolution algorithms such as differential evolution algorithm. The experimental results show that the average ranking of the optimal value of FPEA ranks first among all the compared algorithms on CEC2014 and CEC2019 benchmark functions. The proposed algorithm can achieve the highest solution accuracy with a low computational overhead on four engineering constraint design problems among the compared algorithms including CSA and GPE.

First-order logic-based automatic theorem provers (ATPs) are important for the research on knowledge representation and automatic reasoning, and heuristic strategies are a critical research topic to enhance the performance of ATPs. Mainstream heuristic strategies select clauses by describing clause properties and then determining the priority of the properties. However, the priority of properties is subject to human factors, and it takes a long time to evaluate clauses. A new multi-criteria decision making (MCDM) clause evaluation method was proposed based on the standard contradiction separation (S-CS) rule. Firstly, the entropy weight method was used to objectively assign weights to clause properties. Secondly, preference ranking organization method for enrichment evaluations (PROMETHEE Ⅱ) was combined to evaluate the clauses and obtain the complete order of the clauses. Finally, the proposed MCDM method was applied to ATPs contradiction separation extension (CSE 1.5), Vampire 4.7, and Eprover (E 2.6) to form new ATPs MCDM_CSE, MCDM_V, and MCDM_E. The theorems in first-order form (FOF) from the international theorem provers problem library Thousands of Problems for Theorem Provers (TPTP) were tested on MCDM_CSE, and the Conference on Automated Deduction (CADE) 2022 competition (FOF division) was tested on MCDM_V and MCDM_E. The experiments show that MCDM_CSE proves 151 more theorems (from TPTP) than CSE 1.5 and proves 5 theorems unproved by Vampire 4.7, 41 theorems unproved by E 2.6, and 293 theorems unproved by Prover9. In a shorter average time, MCDM_V proves 6 more theorems (from CADE 2022) than Vampire 4.7, and MCDM_E proves 8 more theorems than E 2.6.

The cell size in the classical cellular automaton-based traffic flow model makes it difficult to express the position relationship of vehicles accurately. Therefore, a scheme to improve the symmetric two-lane cellular automaton (STCA) model by refining the cell size was presented. Firstly, the position, speed, acceleration, and interaction of vehicles in the urban road two-lane environment were analyzed, and the numerical model of these characteristics was built based on the cellular automaton. Especially, the road size and the cellular representation form in the model were improved to solve the problem that the existing traffic flow model based on cellular automaton does not conform to the vehicle driving phenomenon on the actual road. Secondly, according to the real vehicle infrastructure environment, road congestion, lane changing, and other behaviors in the STCA model were redefined, and the lane rules were combined with the refined lane model. A new traffic flow model, namely STCA-CH, was established. Finally, the model was compared with STCA, STCA-I, STCA-S, and STCA-M models, and the validity of the STCA-CH model was verified by analyzing the average speed, average flow, lane changing frequency, and space-time diagram under different vehicle densities. The results show that the lane changing frequency of the STCA-CH model is about 21.14% higher than that of the STCA-M model, and the maximum average flow is about 25.76%, 11.3%, and 3.75% higher than that of the STCA-I, STCA-S, and STCA-M models respectively.

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.

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.

Loose particle accumulations are widely present in nature and industrial production activities. In order to study their mechanical properties and instability processes, acoustic emission (AE) technology was used to explore the evolution law of acoustic characteristics of loose particles in a shear process. Firstly, the AE characteristic parameters of loose particles at different shear rates were analyzed. Then, the AE evolution stages were divided based on the mechanical characteristics of the loading process. Finally, the AE evolution law of loose particles under shear failure was further verified with spectral changes and the proportion of wavelet packet energy. The results show that the energy and ringing count increase gradually with the shear process. The faster the shear rate, the larger the increases of energy and ringing count. The number ratio of small events to large events (b value) decreases gradually during the shear process, and the larger the shear rate, the smaller the b value. The shear strength of particles at different rates is about 140 kPa, and the peak shear force is about 400 N. The changes of ringing count, AE energy, and b value during shear motion are closely related to shear failure stage. The spectral barycenter gradually decreases in the shear process from about 350 kHz to 250 kHz. Meanwhile, the energy proportion of the low frequency band increases, and the energy proportion of the high frequency band decreases accordingly, which results in a spectral barycenter constantly moving down.

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 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.

Finite element model simulation of the rigid 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 rigid OCR model was linearized at the static equilibrium state to avoid the time-consuming rigidity 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 rigid 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%. 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%.

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.

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 response to the problem that direct current (DC) bias current of neutral grounded transformer is affected by dynamic stray current leakage and depot grounding of rail transit, a metro-earth-grid coupling model of stray current distribution and diffusion under multi-train operation was proposed, and the complex image method was used to calculate the earth potential. The self and mutual resistance coefficients of grounding grids were defined, and the coupling relationship between DC bias current and earth potential was proposed. The field-circuit coupling model of earth potential and DC bias current was built according to the topology of stray current intrusion path. A scaled-down simulation test of stray current intrusion into the grid for rail transit was designed, and tests and model calculation were conducted for verification. The results show that the maximum error between the experimental data and the model calculation data is 8.41%. The rail-to-earth transition resistance increases from 3.00 Ω·km to 15.00 Ω·km, and the absolute average of DC bias current decreases by 82.4%. Using a blocking connection device between the car depot and the main line can reduce DC bias current by 23.45% compared with using a unidirectional conduction device.

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.

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.

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%.