Traffic flow stability analysis is the basis for studying the formation mechanism of congestion and platoon control. Linear string stability analysis on mixed traffic flow in connected automated vehicle environment has become a research hotspot in recent years. According to the size and scope of the perturbation, the concepts of linear stability, nonlinear stability, local stability and string stability are introduced respectively. The basic criterion for judging string stability of traffic flow is noted. Based on control theory, the classical analytical methods for the linear string stability condition of traffic flow are reviewed: eigenvalue equation method, which evaluates the growth rate of perturbation in the traffic flow, and the transfer function method, which builds the perturbation transfer relation based on Laplace transform. Then the basic car-following model, the time-delayed car-following model and the multi-anticipative car-following model are introduced. The research on mixed traffic flow stability in China and abroad is systematically analyzed and summarized. The experiments and engineering applications of stability theory in platoon control and other aspects are reviewed. The research prospects are proposed for rear car-following behavior, interaction of connected automated vehicles and complex mixed traffic flow.

In order to solve the constraint difficulty in the railway traffic distribution and route optimization model, and the inadequacy of swarm intelligence algorithm, a constraint optimization method based on penalty function is proposed. First, a virtual arc is set on the basis of the basic model of traffic distribution and route optimization, and the arc segment capability constraints in the model are relaxed by adding a penalty term to the objective function. Meanwhile, a dynamic update strategy is designed for the penalty intensity and penalty factor of the penalty term. Then, the improved grey wolf algorithm (IGWO) is applied to the solution of traffic distribution and route optimization models. Finally, combined with the road network data in a certain area, the models and algorithms before and after improvement are compared and analyzed. The results of case study show that, compared with the model before improvement, after introducing the penalty term, IGWO can find feasible solutions that satisfy the arc capacity constraints within a limited range; compared with the grey wolf algorithm (GWO), the distribution scheme calculated by IGWO reduces the average detour rate of the OD (origin-destination) cargo flow and the total cargo kilometers by 2.6% and 5.2%, respectively.

To make up the deficiency of existing indexes, resilience is introduced as the operation stability index for CTCS-3 (China train control system-3) on-board subsystem under abnormal events. The quantitative evaluation method of on-board subsystem resilience is proposed, the resilience evaluation model based on Bayesian network (BN) is constructed, and five kinds of component importance indexes based on resilience are defined. The bi-directional reasoning function of Bayesian network is used to evaluate the resilience of on-board subsystem under different disturbances and calculate the component importance indexes. The results show that, the resilience index can fully describe the capability of on-board subsystem to resist disturbance or recover from disturbance, and under the disturbance of abnormal events, resilience and availability indexes have marked differences. Different disturbance scenarios lead to obviously different resilience. When disturbance occurs, the resilience of the on-board subsystem is 0.8017 when it is affected by magnetic storm, 0.8819 when it is affected by thunder, and 0.9880 when it is disturbed by snow and ice. The component importance depends on the scenario, specifically, the same component may be varied in the importance ranking in different disturbance scenarios, and may change dynamically with time.

As manual compilation on the maintenance plan of catenary systems is low efficient and hard to optimize, it is converted into a plan optimization problem. An automatic compilation model of catenary maintenance plans is established on the basis of elastic period interval. It uses the integer programming method, considers the continuity of catenary maintenance operation, sets the maintenance status of equipment as the decision variable, and takes the minimal penalty cost and maintenance path cost as the optimization objective.A heuristic algorithm to solve the model is designed on the basis of the hierarchical sequence method in multi-objective planning. The case study shows that this method can realize the automatic compilation and optimization of the catenary maintenance plan, save 99.98% of compilation time and 33.16% of inspection path in comparison with manual work, and improve the compilation efficiency and performance of catenary maintenance plans.

Load process simulation analysis based on the paving operation diagram for urban rail power supply system is significantly different from the actual load process, which cannot accurately reveal many issues in the operation stage of the power supply system. To improve the accuracy of the simulation model, with the train running time in operation diagram as constraints, the objective function with respect to the scheduled energy-saving train operation is established. The target velocity search algorithm with a fixed step is used to optimize the train control sequence and restore the electrical information of the operation diagram with multiple trains. Driven by the actual operation diagram, the load process simulation analysis of the power supply system is performed under normal and abnormal operations. The case study shows that the Pearson correlation coefficient between the simulation results from the actual-track operation diagram and the measured load process curve from traction substations is above 0.89, and the maximum error between the simulated and measured characteristic values in load process is not more than 6.85%, which can improve the accuracy of the simulation results by 12.91% in comparison to the tiled operation diagram.

The thermal dissipation of traction transformers is involved in the conjugate heat transfer between the cooling oil and windings along with the secondary heat release of the heated oil delivered to an oil cooler. To simulate the temporal and spatial temperature variations of traction transformers accurately, the distributed parameter models of traction transformer (including windings and oil) and oil cooler are set up based on the one-dimensional assumption, respectively. The two models are integrated with the lumped parameter ones of oil pump and pipelines. A mathematical model of dynamic temperature field is obtained for the traction transformers. Besides, an iteration algorithm is proposed for the numerical solution. For model validation, a temperature rise experiment is performed on a traction transformer and its cooling system. The results show that the transition time for a stable transformer oil temperature obtained by current model (58 min) meets well with experimental measurement (61 min). The predicted average temperatures of oil and windings under the stable running condition take the discrepancies of 1.3 ℃ and 2.5 ℃ against experimental counterparts, respectively. The current work can be used for the optimal design of traction transformers.

In order to solve the problem that replay attacks in the differential privacy protection mechanism will leak user privacy, a skyline query method based on dynamic page sensitivity adjustment is proposed. First, in order to improve the efficiency of page sensitivity calculation, a method for calculating page sensitivity on the basis of the optimal dominant page is presented. Secondly, to reasonably set the privacy budget value, a privacy budget value adjustment method based on the confidence rate is developed. Finally, the upper bound of query times is dynamically updated based on the privacy budget value, and the skyline query method based on differential privacy protection is realized. The experimental results show that the proposed method reduces the number of leaked private data from 787 to 423 when the privacy budget value is set to be less than 0.8.

In order to investigate reasonable rail gauge and rail cant of No.18 turnout with 60N rail under the straight passing speed 350 km/h, based on the track line method and Kalker’s 3D non-Herz rolling contact theory, key sections of 60N rail turnout and measured LMA worn wheels were used to analyzed the wheel-rail contact geometric and mechanical characteristics under different rail gauges and different rail cant parameters. The calculation results were compared with those of CHN60 rail turnout. The results show that under the premise of ensuring safety, properly widening the rail gauge can improve the wheel-rail matching relationship, improve the stability of the train went through the turnout, reduce the wheel-rail contact stress and surface rolling contact fatigue factor when the wheelset-lateral displacement is greater than 8 mm, and extend the service life of the rail. When the rail cant is 1/30, 1/40 and 1/50, the wheel-rail contact parameters have little difference and the matching performance is better. When the rail cant is 1/10 and 1/20, the lateral irregularity and wheel-rail rolling contact fatigue factors are generally large, and the adaptability of 1/10 rail cant to wheel wear is poor. Compared with CHN60 rail turnout, the equivalent conicity of 60N rail turnout is generally smaller, and the stability of the train went through the turnout is better. Wheel wear is easy to lead to wheelspin in the wheel-rail transition section, resulting in switch rail damage.

In order to explore the design method of the combined stiffness under the baseplate of the elastic indirect fastener system, improve the error and accuracy in the design of the traditional model, based on nonlinear elastic foundation beam, a theoretical calculation model of composite stiffness under baseplate is proposed. First, the nonlinear elasticity of the baseplate pad is introduced into the continuous foundation beam model, and the beam is divided into multiple calculation elements, so as to establish a theoretical analysis model of the composite stiffness under baseplate reflecting the actual deformation and support characteristics of the baseplate. Moreover, the midpoint stiffness method is adopted to solve the deformation of the baseplate and the composite stiffness under baseplate during imposing the installation torque of anchor bolts and the train load. Secondly, mechanical testing machine is used to test the deformation and composite stiffness of DZ Ⅲ fastener system in the real service state, and validate the theoretical model. Finally, the composite stiffness under baseplate of traditional and theoretical calculation models are calculated in different installation conditions (bolt torque) and baseplate design parameters (thickness and bolt distance), and the design error variation of traditional calculation model under different design baseplate parameters is summarized. The comparative analysis shows that, due to neglecting the iron baseplate deformation and nonlinear elasticity under baseplate, the traditional calculation model has a design error range of 37.75%－94.27% within the installation torque range (150－250 N•m), which fails to meet the error requirements of engineering design. The maximum error of the proposed theoretical calculation model is only 2.91%, which meets the requirements of engineering design. When the thickness of the iron baseplate is low or the bolt spacing is wide, the difference between the actual deformation of the iron baseplate and the calculation assumptions in the traditional calculation model will magnify, and the design error of the traditional calculation model will be further increased.

In order to accurately solve the relative displacements of heavy haul freight suspension on a curved track, firstly the mathematical model of curved track was established, and the formulas of outer rail superelevation, slope angle, roll angle and central angle with the length of curve were derived, then according to the time difference and the geometric position difference between the suspension components while the vehicle entering or leaving the curved track, programming to calculate the relative rail superelevation and angle difference of these rigid components. Secondly, the ontological coordinate system was established with the centroid of each rigid body as the origin, and the coordinate expressions of suspension points in the two ontology coordinate systems were given respectively, and converting these coordinates into a same coordinate system through coordinate transformation method, so the transient relative displacement of suspension points could be calculated. Finally, by combining the vehicle curving dynamics simulation, the dynamic relative displacements of suspension points could be calculated. The results indicate that the relative displacement of vehicle suspension is the result of the comprehensive action of vehicle parameters and curve track parameters, when the difference of roll angle difference, slope angle and central angle are excluded separately, the corresponding maximum deviation rate of relative suspension displacement can arrive at 42.85%, 24.03%, and 71.42%. The method of coordinate transformation combined with dynamic simulation can fully consider the vehicle and track parameters, and the relative displacement of vehicle suspension can be solved more accurately.

Rail corrugation not only reduces the ride comfort of passengers, but also increases damages of tracks and vehicles, and even affects the safe operation of trains. In order to verify the correctness of rail corrugation prediction models, firstly the occurrence probability of rail corrugation was calculated based on field investigation data into a metro line and railway main-lines. Secondly, aiming to the shortcomings of the validation method of traditional rail corrugation prediction models, and based on the regularity of rail corrugation occurrence, the benchmark conditions for the verification of the rail corrugation prediction models were proposed, which include the first condition: rail corrugation on the low and high rails at a tight curved tracks whose radii are less than 350 m;the second condition: rail corrugation on the low and high rails at mild curved tracks whose radii are larger than 650 m without Colong-egg fasteners; the third condition: rail corrugation on the two rails of tangential tracks without Colong-egg fasteners. A case study on the prediction of rail corrugation on an actual metro line was performed. Finally, based on whether the creep force is saturated or not, a fast method for predicting rail corrugation was proposed. The research result shows that existing validation conditions for rail corrugation are not universal, that the traditional rail corrugation models neglect the effect of track radii; and that the rail vibration evolution from a new rail without corrugation to the rail with corrugation was ignored in the model validation procedure, which lead to a low model prediction accuracy of rail corrugation. The prediction accuracy of the proposed fast method for predicting rail corrugation reaches 85.00%.

In order to study the effect of high temperature creep on thread load, uniaxial tensile creep tests were conducted on aluminum alloy specimens at normal temperature, 250 ℃, 300 ℃, and 350 ℃. The time-hardening creep model parameters of the aluminum alloy at different temperatures were obtained by fitting the test data. To more accurately describe the working condition of a bolted connection structure in a high-temperature environment, a finite element model of the bolted connection structure was established using ABAQUS, and the effects of linear elasticity, plasticity, and creep on the load distribution were studied. The results show that when the bolted connection structure works in a high-temperature environment, the aluminum alloy material of the connected component creeps and the axial load of the No. 1 thread thus decreases greatly. Considering the material elasticity, the bearing ratio of the No. 1 thread is between 22.88% and 23.15%. Considering the material plasticity, the bearing ratio of the No. 1 thread is between 20.80% and 20.95%. Considering the material creep, the bearing ratio of the No. 1 thread is between 20.65% and 21.02%. Considering the plasticity and creep of the material, the bearing ratio of the No. 1 thread is reduced, and the axial load of all teeth tends to be average.

To study the influence of vehicles on vibration characteristics of large displacement expansion joints, a vertical dynamic model of heavy vehicle-expansion joint coupled system is established, considering the real load characteristics of a wheeled heavy vehicle when passing a large displacement bridge expansion joint. The new fast integration method is introduced to solve the numerical model. Taking ZL1600 modular large displacement expansion joint as the research object, the validity of the model is verified by comparing simulation results with test results. Based on the model, the impact effect of wheeled heavy vehicle on expansion joint is analyzed. The results show that the dynamic model simulation results of vertical velocity at the center beam test points can be well matched with the test results. The deviations of center beam maximum sinking displacements between simulation results and test results are less than 10.0%, which indicates that the model has high calculation accuracy. The maximum impact factor of tire loads occurs when the wheel drives on the bridge deck behind the expansion joint. Therefore, it is necessary to strengthen the nearby structure. The impact factor of tire loads on the center beams and the rear bridge deck increases with speed. The maximum impact factors are 0.67 and 0.82 respectively, both exceeding the recommended value of 0.45 in the current Chinese standard. It should be given more attention.

In order to improve the calculation accuracy of the natural frequency of thin-walled box beams, the dynamic characteristics of thin-walled box beams are analyzed using the generalized coordinate principle. Firstly, the free vibration differential equations of five highly coupled modes (i.e., extension, bending, torsion, warping and distortion) are obtained by the virtual work principle and considering the influence of the distortion deformation. Secondly, considering the influence of the rotational inertial motion term, the kinematics model under the simply supported boundary condition is established. The fourth order algebraic equation of free vibration of the thin-walled box beam and the exact solution of the natural frequency are obtained. Finally, a numerical example is provided to compare the exact solution of natural frequency considering distortion with the results of Prokić theory and finite element analysis, so that the effectiveness and accuracy of present method are verified. The results show that when taking the distortion effect into consideration, the natural frequency of free vibration of the thin-walled box beam can be more accurately reflected in high-order modes. Comparison of natural frequencies at four orders of the free vibration indicates that when the length of the box girder is 3 m, the relative error of the present theory was reduced to 0.38% from Prokić’s 0.42%; when the length of the box girder is 4 and 5 m, the relative error can be further reduced to 0.30% and 0.40%, respectively.

To explore chloride ion erosion in the crack propagation process of concrete structures under loads, and more accurately describe the characteristics of chloride ion erosion around cracks at different stages, the development process of concrete trabeculae type Ⅰ fracture, based on the concrete fracture criteria, was simulated by self-programming, and redeveloped by ANSYS parametric design language APDL. Given the mapping relationship between volume strain, damage variable and chloride ion diffusion coefficient, the parameter equivalence method and the structure-thermal analysis method are used for numerical analysis of chloride ion erosion at various stages of concrete crack propagation. The results show that chloride ion erosion around the crack of a three-point bending concrete trabecular is consistent with the experimental one at different crack-expanding stages. The chloride ion erosion at the crack tip of concrete is intensified under loads; therefore, it plays a decisive role in the durability life analysis of concrete structures. Furthermore, the double-K fracture criterion and the chloride ion diffusion model based on damage parameters can simulate the chloride ion erosion in the concrete cracking process.

The self-healing performance of cement mortar specimens at different ages and temperatures was tested by compressive strength repair rate, crack repair rate, and electrochemical impedance spectroscopy (EIS), and then was analyzed using the scanning electronic microscope (SEM) to study the microscopic self-healing mechanism of magnesium acrylate cement-based materials. The test results showed that the effect of magnesium acrylate on the compressive strength repair and apparent repair of the mortar specimens was not obvious at the early age. The effect on compressive strength repair intensifies gradually with the increasing age, and the apparent crack repair rate at 7 d reached 100.0%. Meanwhile, medium-high temperature was beneficial to self-healing effect, but the effect above 40 ℃ was no longer significant. EIS showed that the equivalent circuit parameters of the test group at the age of 28 d were better than those of the control group; the repair effect of the magnesium acrylate at old age is significantly better than the "healing" effect brought by the hydration reaction of cement-based materials.

In order to explore the influence of constitutive models on the surface settlement induced by shallow tunnel excavation, the surface settlement trough induced by shallow tunnel excavation in composite layered strata was analyzed considering the friction and critical state soil constitutive model. Firstly, a numerical model of shallow buried tunnel in sand clay composite stratum is constructed on the finite element platform PLAXIS 3D. Three types of constitutive models (i.e., the Mohr-Coulomb model (MC), the modified Cam-Clay model (MCC), and the hardening small strain model (HSS)) and their combinations are utilized. Secondly, the influence of the constitutive model on the width and depth of the ground settlement trough in tunnel excavation is discussed using the parameter equivalent transformation relationship. Finally, the numerical simulation and empirical calculation results of the settlement trough based on the three types of constitutive models and their combined models are compared, and the reasons for their differences are analyzed. The results show that when the HSS model is used for both the upper and lower strata, the maximum settlement and the width of settling trough obtained by numerical simulation are in good agreement with the calculated results by empirical formula, and the difference in the maximum settlement between the two approaches is less than 7.3 mm; when the MC model is used for both the upper and lower strata, an unreasonable phenomenon of surface uplift appears; when the MCC model is used for the lower stratum while the MC model and HSS model are used for the upper stratum, respectively (i.e., when the MC-MCC and HSS-MCC combined models are used), the maximum settlement predicted by numerical simulation is 24.8 mm higher than that calculated by empirical formula, while the settlement trough is "narrow and steep" compared with the empirical result. According to the parametric sensitivity analysis of the HSS model, it is found that a change of 5% in the unloading and reloading modulus and initial shear modulus will lead to a change of 1.5% and 1.0% in the maximum ground settlement, respectively.

Corroded rock mass usually plays a key role in controlling the stability of rock mass engineering. In order to reveal the evolution law of anisotropic mechanical properties and failure characteristics of the bedded rock mass suffering corrosions, indoor uniaxial compression tests were carried out on rock masses with different corrosion rates (K = 0%, 5%, 10%, 15%, 20%) to obtain their compressive strength and elastic modulus at different included angles (α = 0°, 30°, 45°, 60°, 90°) . Based on the test results, mathematic models for predicting the compressive strength and elastic modulus of the corroded rock mass with beddings were established and then validated by experiment. The results show that the compressive strength achieves its maximum value at the included angle α = 0°, 90°, and achieves its minimum value at α = 45°, presenting a symmetrical U shape as a whole; while the elastic modulus is the smallest at α = 60° and the largest at α = 90°, showing an asymmetric U shape as a whole. The anisotropy indexes of compressive strength and elastic modulus (i.e., RP and RE) of the intact rock mass are the largest, which are 1.98 and 3.05 respectively, and their values gradually decrease with the corrosion rate increasing. When K = 20%, RP and RE are 1.10 and 1.36, respectively. The deformation and failure of rock mass with small corrosion rates are controlled by rock matrix and beddings, mainly by splitting, staggered shear and sliding shear. As the corrosion rate increases, the deformation and failure are obviously controlled by dissolution pores and skeleton, and the skeleton swelling, shear dislocation and crushing failure are the main types.

A highway tunnel under construction in Honghe Prefecture, Yunnan Province was taken as the research object to study the geological genesis of high ground temperature. The tunnel has both high water temperature and high rock temperature, with the maximum water temperature of 63.4 ℃ and the maximum rock temperature of 88.8 ℃. The regional thermal control, water source, heat source, and heat conduction channel are analyzed from the aspects of regional geological structure, seismic characteristics, hydrochemical characteristics, and geothermal reservoir characteristics. The hot water source, evolution process, and origin of heat source are studied by means of hydrogen oxygen isotope analysis, strontium isotope analysis, trace element analysis, and radioactive element analysis. Based on the geological, hydrogeological and excavation conditions of the tunnel, the geological genesis of the high water temperature section and the high rock temperature section of the tunnel is dissected and discussed. The results show that the genetic process of high water temperature in limestone sections is different from that in granite sections. The genetic process of high water temperature in tunnel is “heat source (deep thermal anomaly)–main heat transfer channel (deep cycle)–secondary heat transfer channel–shallow water mixing and water rock interaction”, which is accompanied by cold and hot water mixing, ion exchange, etc.; while the genetic process of high rock temperature in tunnel is “heat source (deep abnormal body, radioactive element decay heat generation)–main heat transfer channel (deep cycle)–secondary heat transfer channel–hot gas being transmitted to the tunnel rock mass along the crack”, and the process is accompanied by the enrichment of S element, which is favorable to the formation of toxic and harmful air bag of H₂S or SO₂.

Discrete element analysis method is one of the important tools for studying rock mechanics behavior and refining the basic theory of rock mechanics. In order to improve the accuracy of the particle discrete element method to simulate indoor rock mechanics and large-scale engineering scale tests, a layered modeling method is proposed. This method adopts small-size particles for fine simulation of the rock or key rock mass area, and large-size particles for the outside area to expand the calculation area. The layered modeling method is used to carry out uniaxial compression and Brazilian splitting tests, and compared with the conventional modeling calculation results, which preliminarily verifies its feasibility to simulate indoor mechanical tests. The results show that the layered modeling method is affected by the particle size like conventional modeling, but it can reduce the number of particles in the particle flow code model and increase the calculation efficiency by more than 50%. The uniaxial compressive strength and crack initiation stress of the layered model are reduced by only 2.7% and 1.9% at most, compared with those of the conventional model with the corresponding outer layer. The coefficient of variation (COV) of uniaxial compressive strength and crack initiation stress is generally larger than that of the conventional model, but it is still within the acceptable range of 2%. The inhomogeneity of particle size distribution in the layered model has minor effect on the deformation properties of the model at the elastic stage, and the elastic modulus of the layered model is reduced by 1.3%−2.3% compared with the conventional model with the corresponding outer layer. The overall Brazilian splitting tensile strength of the layered model is increased by 1.32%−2.35% compared to that of the conventional model with the corresponding outer layer, and the macroscopic fracture characteristics are similar to those of the conventional small-particle model, but there are more cracks near the loading plate.

As there is a lack of automatic search method for trestle positions of freight cableways, three methods, namely convex-point traversal method, terrain adaption method, and interference-point search method, are proposed, all of which can search trestle positions automatically on two-dimensional terrain profile. Of them, the convex-point traversal method treats all the convex points on the profile as potential trestle position, and obtains the trestle position by screening the redundant trestle. The terrain adaption method determines the trestle position by the interference condition between the carrying rope curve of the cableway and the terrain during the descent of the carrying rope. In the interference-point search method, the trestle positions are picked by adding intermediate trestle at the maximum interference position between the carrying rope curve and the terrain. The success rate of these methods are 9.12%, 8.38% and 8.26%, respectively, which show little difference. However, the search speed of the interference-point search method is 5.8 times and 3.5 times the convex-point traversal method and the terrain adaption method, respectively. Therefore, in field applications, it is suggested to use the fastest interference-point search method to search the trestle position for the freight cableway of transmission lines automatically.

In order to find out the long-term effects of train load on the composite stratum of clay and silt and the metro tunnel in it, the dynamic response characteristics of this kind of composite stratum under a metro tunnel in a typical section of Wuxi Metro lines due to the moving train were firstly studied through a 2.5-dimensional (2.5D) track-tunnel-ground coupling model. Based on this, combined with the undrained deformation accumulated characteristics and the pore water pressure accumulated characteristics of corresponding soils under the cyclic loading, the developments of the long-term settlements of the concerned composite stratum and the tunnel structure due to the train vibration loads were finally obtained and analyzed through the layered summation method. The analysis results show that: 1) the dynamic deviatoric stress of the foundation soil under the tunnel increases first and then decreases with the increase of the depth, and its maximum value can reach 2.8 kPa, which appears at the position with a distance of 1.3 m to the tunnel invert; 2) the train-induced settlement of tunnel structure in the composite stratum mainly occurs within the first 200000 operation periods of metro trains, and it develops rapidly during these periods; 3) the stable train-induced settlement of tunnel structure in the composite stratum has a magnitude of 13.44 mm, in which the part caused by the accumulated undrained plastic strain of soil is 11.40 mm, accounting for 85% of the total value, while the part caused by the dissipation of accumulated pore water pressure and the corresponding consolidation of soil is 2.04 mm, accounting for 15% of the total value; 4) the long-term deformation of the composite stratum of clay and silt mainly occurs within 15 m below the tunnel, and the contribution of soil settlement within this range to the magnitude of the long-term settlement of the tunnel structure can account for 90%.

To meet the new requirements of bridge piers for rapid repair after earthquake and improve the suitability of precast segmental bridge piers in medium and high intensity areas, a precast segmental concrete filled steel tube (CFST) bridge pier with external replaceable energy dissipation devices was proposed. Based on the ABAQUS software, the analysis models of the post-tensioned prestressing precast segmental CFST piers with three segments were established. The seismic performance of the precast segmental CFST piers with the energy dissipation devices of three different control parameters (section contribution rate, slenderness ratio and arrangement) was analyzed under cyclic loading. The results show that the precast segmental CFST piers can be rapidly repaired by replacing energy dissipation devices and other measures due to the damage level of piers can be controlled by using external energy dissipation devices. Compared with the pier without energy dissipation device, the lateral strength, initial stiffness and energy dissipation capacity of the precast segmental CFST piers with external energy dissipation devices are increased 11%−88%, 2.86%−6.87% and 2.3 times−12.9 times, respectively. Meanwhile, to ensure the feasibility of repair after an earthquake, it is suggested that the section contribution rate of the external energy dissipation devices should not exceed 1.9%. Due to the small diameter of the energy dissipation bar on the middle joint which will cause the energy dissipation bar at pier bottom to not be fully utilized, it is suggested that the reduction factor of the energy dissipation devices along the pier height should not be less than 0.5. The change of slenderness ratio of energy dissipation bars has an effect on the lateral strength and ductility of the piers. With the decrease of the slenderness ratio, the energy dissipation capacity increases but the residual displacement of the piers also increases gradually. It is suggested that the slenderness ratio of energy dissipation bars should be greater than 4.5.

To accurately investigate the distortional effect of single box double-cell box girders (SBDBG) under vertical eccentric load, the concepts of antisymmetrical and positive-symmetrical distortion were introduced, and the distortional assumption of rectangular cross section of SBDBG was supplemented. The antisymmetrical and positive-symmetrical distortion of SBDBG were described by different definitions of distortional angles. The distortion of SBDBG was researched by plate element analysis and energy variation methods. Two parameters were used to describe the distribution of stress on top, bottom, and web plates respectively to adapt to the positive-symmetrical distortion. The influence of positive-symmetrical distortion on SBDBG was considered, compared difference of distortion effect between single-cell and double-cell box girder, discussed variation of distortional angle along the length of SBDBG with the change of mid-web thickness. The results show that the analytical solution of SBDBG distortion is more consistent with the finite element solution when considering the influence of positive-symmetrical distortion, the error is less than 8.71%. The normal stress of positive-symmetrical distortion is small, and the maximum is only 28.08% of the antisymmetrical distortion. The mid-web can effectively reduce distortion effect caused by eccentric vertical load, and make the distortion normal stress decrease to 49.09% of the single-cell box girder. The distribution of the distortional normal stress on each plate is more reasonable when using two parameters to describe the positive-symmetrical distortion. The change of the mid-web thickness can make the SBDBG distortion alter obviously, and distortion will gradually decrease when the thickness increases.

A cable opening inspection was made on a suspension bridge in service for 25 years in Myanmar to analyze the corrosion status and residual bearing capacity of the main cables. First, the outer protection layer of the main cable was removed; the main cable is partially split with wedge for detection, and the corrosion distribution diagram of the main cable cross-section was established. Then, the main cable steel wire of the bridge was divided into four corrosion stages, and samples of each stage were taken from the cable for laboratory analysis. Finally, a simplified model was used to evaluate the residual bearing capacity of the main cable. The results showed that the corrosion degree of the steel wires decreased from outside to inside along the radial direction of the main cable, and the outermost steel wire had serious matrix corrosion. As the corrosion level increased, the corrosion spot size of the sample steel wires expanded gradually, the strength and ductility of the steel wires decreased by about 3.50% and 9.00%, respectively, and the average tensile strength of the upstream and downstream main cables decreased by about 5.7%.

To analyze the restrained torsion effect of the box girder with corrugated steel webs (CSWs) more reasonably, the calculation formulas of warping normal stress and shear stress were deduced considering the accordion effect of CSWs. Moreover, the governing differential equation for analyzing the restrained torsion was established using Reissner’s principle, and the warping coefficient formula differing from Umanskii’s second theory was presented. The calculation formulas were then verified through a numerical simulation of a simply supported box girder, and the influence of web thickness and cantilever slab width on cross-section stresses of the box girder was analyzed. The results show that the stresses calculated based on Reissner’s principle are in better agreement with the finite element solution than those based on Umanskii’s second theory. The ratio of warping coefficient calculated by Umanskii’s second theory to that calculated by Reissner’s principle can reach 4.70. CSWs mainly bear shear stress and almost no warping normal stress, while top and bottom slabs bear both warping normal stress and shear stress. Therefore, more attention should be paid to top and bottom slabs to prevent oblique cracks. In addition, growing web thickness can reduce warping normal stress. With the increase of the cantilever slab width, warping normal stress decreases when the cantilever slab width ratio is above 0.10, while the total shear stress hardly changes when the cantilever slab width ratio is above 0.30.

In order to solve the problem that traditional geophysical methods are difficult to achieve better detection and monitoring of stratum disturbance in urban shield tunnel engineering, the application of active source Rayleigh surface wave elliptical polarization method is proposed. Firstly, the 2D finite element numerical simulation is used to simulate the full-wave field forward modeling of the stratum under the actual shield tunnel construction background, and the characteristics of wave field propagation, velocity dispersion and elliptical polarization dispersion are analyzed. Then, the elliptical polarization method and the traditional velocity dispersion method are further analyzed and compared on the basis of a combination of examples. The results indicate that the active source Rayleigh surface wave elliptic polarization method has the same detection effect as the traditional velocity dispersion method in detecting the distribution of underground medium structure and monitoring the changes of underground cavity and other abnormal structures. However, because it does not need the arrangement of long and long geophones, it has relatively strong anti-interference ability to the vibration and other noise of the surrounding environment. Therefore, it is more suitable for the environment with limited sites such as cities and certain vibration and noise interference, so it has a broader application prospect.