Abstract:To improve the application of weathering steel in bridge constructions, corrosion fatigue test can be adopted as an effective approach to investigate its fatigue performance under corrosion. First, the classification of the corrosivity of environment, uniform corrosion, and pitting corrosion were introduced, and the effects of corrosion on the fatigue performance of steel were briefly described. Next, three typical types of fatigue tests were reviewed, and results of both domestic and international studies were summarized and analyzed. Then, the content of corrosion fatigue test was summarized, including design of steel specimens, corrosion test methods, and fatigue test methods. Finally, a series of fatigue tests were carried out on 20 corroded HPS 485W and Q345CNH steel specimens, and results were compared with naturally corroded weathering steel specimens. Results indicate that corrosion environment can greatly influence the corrosion of steel, in which the pitting corrosion is a critical factor that can induce the initiation of fatigue cracks. Meanwhile, relevant experimental studies need to be carried out orderly and hierarchically although there are many different kinds of corrosion fatigue test methods. Besides, the design optimization of specimens should be made based on the related codes, and it is critical to take into account of the excessive energy dissipation of specimens during fatigue tests. In experiment process, a reasonable control of corrosion environment conditions is crucial to guarantee the expected test results. It is worth noting that the fatigue strength of the weathering steel specimens decreased significantly after the salty spraying dry/wet corrosion test, and the scatter in data was notably reduced compared with those of uncorroded specimens. Based on the combination of natural corrosion test and accelerated corrosion test, the progresses from weathering fatigue test to corrosion-fatigue test and from small specimen to structural specimen can be gradually realized.

Abstract:To provide theoretical reference for the research and development of advanced driving assistance system (ADAS) and unmanned driving technology, the statistics of foot manipulating behaviors of urban road drivers in China under natural driving conditions were obtained and modeling analysis was carried out. Based on the data, the dynamic EEG change rate (EEGδ), heart rate change rate (Hδ), and EMG change rate (EMGδ) were used to reflect the transient and cumulative characteristics of driver’s physiological states. The relations between the driver’s accelerator pedal force and brake pedal force with main physiological indexes were fitted, which is the driver’s foot manipulation behavior model. The model verifies the correlation between accelerator pedal force, brake pedal force, and main physiological indexes during driver’s foot manipulation. The rules of pedal trampling frequency in natural driving conditions were statistically analyzed. Results show that urban road drivers preferred to control speed through braking force. The accelerator pedal force and brake pedal force were positively correlated with indexes EEGδ, Hδ, and EMGδ. The pedal trampling frequency had obvious relations with different driving years, genders, and ages. The model can be applied for the development of driving assistance system, simulation of driver’s manipulating behaviors, and research of automatic driving technology based on driver control behaviors, as well as the design of intelligent vehicle technology on the basis of driver’s manipulating rules.

Abstract:In view of the low efficiency of green time utilization in the traditional arterial coordinated signal control method which only conducts speed guidance under connected vehicle environment, based on the two-way information interaction between vehicles and infrastructures, a new arterial coordinated signal control method was proposed with the goal of forming a saturated traffic flow by considering the two-way optimization of speed guidance and signal control scheme. On this basis, the arrival time range of the vehicles to be processed at each intersection in each cycle was defined, and the delay and stops of the vehicles were weighted to form a comprehensive performance evaluation index (PI). The optimization model of signal control parameters was established based on the minimum average PI, and the solution algorithm was designed. Case study shows that compared with the traditional arterial coordinated signal control method that only conducts speed guidance, the proposed method reduced the average PI of vehicles at intersections by 11.2%, which verifies the validity and feasibility of the model. The sensitivity of the optimization model was analyzed from the aspects of speed guidance interval, average travel speed, and intersection spacing, and the applicable conditions of the model were determined. Results show that these factors had significant influence on the optimization results of the signal control method.

Abstract:To determine the reasonable integrity quality evaluation time of cement-treated aggregate base (CTAB) layers, eliminate the influences of curing conditions, gradation types, and design strengths (cement dosage), and make up the limitations of using fixed age to evaluate CTAB construction quality, large specimens with three types of gradations and three kinds of cement dosages were molded by vibration method for experiment. After using three kinds of curing paths to preserve, the coring and splitting strength tests were carried out, and the relationship between maturity and splitting strength was established. Experiment results show that cement dosage (mass fraction) had a great influence on the age at which an intact core could be taken out. When the cement dosage was 5.5%, intact cores could be taken out from specimens of all three gradation types in seven days; when the cement dosage was 4.5%, intact cores could be taken out from specimens with suspend-dense structure grading until 14 days; as the cement dosage dropped to 3.5%, intact cores were failed to be taken out under the three gradation types in seven days. When the gradation tended to suspend-dense structure, the side walls of cores were less dense. Intact dense cores could be taken out in seven days, only when the cement dosage was above 5.5% under suspend-dense structure grading, otherwise the curing age must be increased. Whether the intact cores of CTAB could be taken out was closely related to splitting strength, when the splitting strength reached the coring critical strength, intact dense cores could be taken out. There was a hyperbolic relationship between the splitting strength of CTAB and the maturity curve under different curing paths. Based on the coring critical splitting strength and the relationship between splitting strength and maturity, the critical maturity standard of coring was put forward. It is feasible to use coring critical maturity to scientifically determine the integrity quality evaluation time of CTAB.

Abstract:To compare and evaluate the adhesive self-healing properties of different asphalt and explain the mechanism of asphalt self-healing from micro-level, the binder bond strength (BBS) test was conducted on seven base asphalt binders and four types of modified asphalt with different dosages (SBS, terminal blend rubber, gilsonite, and high-density polyethylene). Fourier transform infrared (FTIR) test was carried out on selected asphalt, and the mechanism of self-healing was analyzed by asphalt molecular chain structure index (methylene plus methyl hydrogen to carbon, MMHC). The correlation between viscosity of asphalt and self-healing performance was obtained. Results show that the adhesive self-healing properties of different base asphalt binders after multiple failure-healing cycles were significantly different. High-density polyethylene and gilsonite at low dosages could improve the self-healing property of asphat, whereas linear, radial SBS, and rubber powder had negative effect on the adhesive self-healing property of asphalt. There was a significant negative linear correlation between MMHC index and healing ratio of base asphalt. However, the MMHC index could not be used to predict the adhesive self-healing property of modified asphalt. The Brookfield rotary viscosity of base asphalt and modified asphalt at 135 ℃ both showed good linear correlation with their healing ratio. Compared with MMHC index, Brookfield rotary viscosity at 135 ℃ is a more suitable evaluation indicator for predicting the adhesive self-healing property of asphalt.

Abstract:To analyze the influence of dynamic vibration absorber beneath rail base on the sound radiation characteristics of the rail, a vibration-acoustic radiation model for rails was established. First, three-dimensional solid finite element model was established according to the actual topological structure of the railway slab track, and the eigenvalue problem of the rail structure was solved by the direct method. Next, the admittance characteristics of the rail and the decay rate on the track under vertical unit force excitation were calculated and analyzed. Then, the wheel-rail rolling noise prediction model was used to calculate and analyze the influence of rail vibration absorber on the sound radiation power of the rail. Finally, the influence of the parameters of dynamic vibration absorber beneath rail base was analyzed. Results show that the vibration reduction effects of the dynamic vibration absorber beneath rail base were at the frequency band of 750 Hz to 1 650 Hz, and the noise reduction was above 800 Hz. The larger the mass ratio of vibration absorber was, the higher the level of vibration reduction and noise reduction was, while the lower the efficiency improvement of vibration reduction and noise reduction was. Increasing the stiffness of the vibration absorber in a certain range could slightly improve the noise reduction level, whereas too large stiffness could aggravate rail vibration response and its longitudinal propagation. The damping coefficient could affect the frequency bandwidth of vibration reduction and noise reduction, so it needs to be large enough to match the mass and stiffness of the vibration absorber. The calculation and analysis in this paper can provide certain reference for the parameters design of rail dynamic vibration absorbers and the selection of low-noise rails.

Abstract:To meet the objective demands of changing lanes in super-long tunnels adjacent to interchanges, and to solve the problems of lane control and length control in traffic organization, through the analysis of the critical safety status of anti-sideslip and anti-overturning, a model was established based on the minimum headway to calculate the minimum safe distance for lane changes in super-long tunnels or connection sections. Aiming at the requirement of double lane changes for three-lane one-way tunnels and above, in order to ensure a safe distance between front and rear vehicles for lane changes, a probability model was constructed for single and double lane changes to measure the success probability of safe lane changes in connection sections. Aided by the Vissim simulation technology, the analogy analysis of traffic organization methods and lane control methods of super-long tunnels was carried out. Considering the operating safety and traffic efficiency of super-long tunnels, the traffic organization methods could be selected based on the indicators of vehicle delay, lost time, average speed, and the number of lane changes, and the lane control methods could be selected based on the average delay per vehicle, the number of parking times per vehicle, vehicle density, delay ratio, and driving speed. Results show that the minimum distance of connection sections of super-long tunnels adjacent to interchanges should be checked for the minimum distance of safe lane changes, and the success probability of single and double lane changes should be measured based on the safe distance. For the connection sections which cannot meet the length requirements, the traffic organization method that the off-ramp vehicles complete the lane changes in the super-long tunnels is suggested.

Abstract:To explore the mechanical behaviors of surrounding rock-grouting ring-lining system in deep tunnel under non-linear seepage condition, Izbash non-linear seepage model was introduced and the hydraulic head distribution of surrounding rock-grouting ring-lining system was given. Based on the unified strength theory and considering the possible location of plastic zone, the displacement, stress, and radius of surrounding rock plastic zone under grouting and lining support were deduced theoretically. Theoretical results and numerical solutions were compared through an example and feasibility of the theoretical method was verified. The engineering significance for the supporting design of mountain tunnel with rich water considering non-linear seepage was further discussed. Results show that the influence of non-linear seepage on elastoplastic mechanical effect of tunnel was mainly reflected in the hydraulic gradient coefficient m₁ of surrounding rock. In the process of the transition from low-speed non-linear seepage to high-speed non-linear seepage, the radius and displacement of plastic zone became larger, and the stress of surrounding rock decreased. The thickness design of grouting ring and lining support should be considered from the perspective of non-linear seepage of surrounding rock. The research results provide a theoretical basis for the support design of non-linear seepage tunnel.

Abstract:Since regional bridges are widely distributed and large in quantity, it is difficult to comprehensively evaluate them. This paper establishes a condition assessment theory for regional bridges based on the integrated multi-source information of single bridge. The database of regional bridges is stored within a “route-bridge-component” formation, which is extracted from inspection reports, monitoring systems, traffic data, design drawings, and so on. Based on the integrated multi-source information of regional bridges, the performance evaluation of the regional bridges and network-level assessment can be carried out. Taking a partial highway in Hebei province as an example, three sub-regions were divided according to climate characteristics, and the overall and regional characteristics of the road network were evaluated. Data mining was carried out concerning key parameters such as bridge type, age, and traffic volume, and correlation analysis was conducted between these parameters and general technical scoring at network level. The proposed framework provided data basis and analysis conditions for network-level evaluation. Results indicate that the proposed data integration and mining methods can effectively reveal the common features and deterioration rules of regional bridges, and hence can be used for network-level assessment of regional bridges.

Abstract:To obtain a more accurate method for analyzing the crack width in negative moment regions of steel-concrete composite beams, a numerical calculation model of crack width under static loading based on bond-slip theory was established, considering the bond-slip relationship between reinforcement and concrete, the slip effect between steel beam and concrete slab, concrete shrinkage strain, and tension-stiffening effect. The predicted values of the model were compared with related literature data and the calculation results of standard formulas. Results show that the calculated values of the proposed model could well simulate the development process of crack width before the composite beam reached the yield load. The suggested model appeared to provide unreliable predictions that the crack width increased by 10% when the slip effect at the beam-slab interface was not considered. Compared with the experimental values, the results obtained from the standard formulas had a large deviation. While the results obtained from the proposed numerical calculation model were in good agreement with the measured values, and the dispersion coefficient was the minimum, which verified the accuracy and applicability of the model.

Abstract:To analyze the bonding and anchoring performance of the connecting steel bars of prefabricated concrete bridges and concrete, the steel bar diameter, concrete strength, and anchorage length were taken as test parameters, and 22 pullout test pieces were fabricated for experimental research. The finite element model of the reinforced concrete bonding interface was constructed to analyze the influence of various parameters on the bearing capacity and bonding strength of the test pieces. Based on the experimental data and finite element results, the bonding strength calculation formulas for the connecting steel bars of prefabricated reinforced concrete bridges were fitted and derived. The relevant regulations of domestic and foreign standards for the anchorage length of steel bars were compared and analyzed, and the recommended value for the basic anchorage length of connecting steel bars of prefabricated concrete bridges under different concrete strength levels was given. Results show that for the connecting steel bars of prefabricated components, the bearing capacity of the interface between steel bar and concrete had positive relations with concrete strength, steel bar diameter, and anchorage length. The interface bonding strength was positively correlated with concrete strength, negatively correlated with steel bar diameter, and had little relation with anchorage length. The influence of the anchorage length and the thickness of the protective layer can be ignored when calculating bonding strength.

Abstract:To provide timely alerts for the unexpected surges of passenger flow in urban rail transit, an anomaly detection method was proposed based on the smart card data collected by the automated fare collection system. First, the length of the sliding time window was determined in light of the time-varying characteristics of passenger flow to adapt to the dynamic data environment. Then, a deep belief network model was developed to extract the features hidden in the target sample, and further recognize the pattern of the target sample within the time window. Finally, by mapping the target sample and the historical samples of the same pattern to a multi-dimensional feature space, the anomalies in metro passenger flow could thus be identified in terms of local outlier factor. According to the case study of Guangzhou Metro, results show that the pattern recognition accuracy of the proposed method was 92.5% and the anomaly detection false rate and accuracy were 3.98% and 91.9%, respectively. The detection performance of the method was related to the forms and degrees of the anomalies, and affected by the acceptance criteria of the response time. Overall, the proposed method could accurately detect a broad range of anomalies in the cost of a comparatively low false rate.

Abstract:To study the influence of desert sand on the frost resistance of concrete, the compression strength experiment of desert sand concrete after freezing and thawing test was carried out by rapid freeze-thaw method. The stress-strain curves and failure characteristics of desert sand concrete after different freeze-thaw cycles were obtained. The variations of surface damage characteristics, mass loss rate, dynamic elastic modulus loss rate, and ultrasonic wave velocity loss rate of desert sand concrete were analyzed. Experimental results show that with the increase of the number of freeze-thaw cycles, the mass loss rate of desert sand concrete had little change; the dynamic elastic modulus loss rate, ultrasonic wave velocity loss rate, relative peak strain, and ultimate strain increased; the relative peak stress and transverse deformation coefficient declined; the elastic modulus increased firstly and then decreased. With the same number of freeze-thaw cycles, the dynamic elastic modulus loss rate, ultrasonic wave velocity loss rate, and relative peak strain of desert sand concrete were less than those of ordinary concrete. However, the relative peak stress, transverse deformation coefficient, and elastic modulus of desert sand concrete were higher than those of ordinary concrete. On the basis of the uniaxial compression constitutive model of concrete put forth by Guo Zhenhai, the equation of stress-strain full curves was formulated. The influence of freeze-thaw cycles on the control parameters of stress-strain curves was analyzed, which can be applied for the frost resistance analysis of desert sand concrete structures.

Abstract:To investigate the influence of subgrade frost heaving deformation on track irregularity and structural stress, based on the ANSYS finite element analysis method and the research on the subgrade section of the frost heaving zone of the Harbin-Dalian high-speed railway, the spatial refinement finite element model of CRTS I type ballastless track was established by considering the characteristics of limit boss, gel resin, and interlayer contact. On this basis, effects of the locations of frost heaving deformation and different frost heaving wavelengths and amplitudes on the ballastless track structure were discussed, and the track irregularity, interface crack characteristics, and static performance were analyzed. Results show that under short-wave frost heave, indicators of irregularity, deformation, interface crack, and stress of the ballastless track structure increased with the decrease of the frost heaving wavelength and the increase of the frost heaving amplitude. When the frost heave occurred in the center of the baseplate, the stress on the track structure was the most affected, and when the frost heave occurred in the baseplate expansion joint, it had the greatest effect on the deformation and interface crack of the structure. Compared with the track slab, the baseplate bore the largest tensile stress, and the structural stress was more affected when the frost heave occurred in the center of the baseplate. In terms of the tensile strength of the ballastless track, the baseplate was the limited structure, and the frost heaving limiting values ware recommended to be 10 m for wavelength and 5 mm for amplitude.

Abstract:To investigate the subgrade mud-pumping of ballastless track for high-speed railway, a full-scale model test system was built. The moisture content, matric suction, and excess pore water pressure of the subgrade during the process of subgrade mud-pumping were measured, the hydrodynamic pressure characteristics of the subgrade were analyzed under dynamic loads induced by high-speed trains, and the mechanism and influencing factors of subgrade mud-pumping of ballastless track were evaluated. Results show that the subgrade surface layer of ballastless track was basically saturated after rainfall infiltration. The mud-pumping was likely to happen under the dynamic loads of high-speed trains. The subgrade mud-pumping occurred with an increase in excess pore water pressure, and the increment of excess pore water pressure was constant in the mud-pumping region with an increase in the depth of subgrade surface layer. In saturated situation, the excess pore water pressure of the subgrade on both sides of the concrete base was higher than that below the center line of the subgrade, making mud-pumping more likely to occur. Reducing the water content or pore water pressure of subgrade can be an effective way to control and prevent the occurrence of subgrade mud-pumping.

Abstract:To improve the construction safety of aeolian sand tunnels, construction simulation was carried out based on the Wangjiawan Tunnel of Menghua Railway to investigate the stability changes of surrounding rocks. Laboratory tests were conducted by using the soil taken from the site to obtain the physical and mechanical characteristics of the surrounding rock. Based on the discontinuity of sandy surrounding rocks, the discrete element software was adopted to simulate the construction process of aeolian sand tunnels with different relative compactness, and the dynamic changes of surrounding rock stress and the development of the loose zone were monitored and analyzed. Results show that the range of the advance displacement of the surrounding rock in front of the tunnel face was positively correlated with the relative compactness of the surrounding rock, and the disturbed range above the vault was negatively correlated with the relative compactness of the surrounding rock. Face failure was prone to occur in dense aeolian sand tunnels, and the risk of collapse in loose strata was high. The excavation of the aeolian sand tunnel mainly disturbed the surrounding rock within 2/3D-D in front of the face, around the tunnel, and within 0.5D-D above the tunnel. When the relative compactness was 0.5 and 0.7, the failure modes of the surrounding rock were basically the same as that adopted in “Code for design of railway tunnel (TB 10003—2016)”. When the relative compactness was 0.9, the form of surrounding rock instability was approximately ellipsoidal. The stability of the surrounding rock of the aeolian sand tunnel was closely related to its compactness. The tight combination of the meso-particles could effectively resist the external force, which shows the stability of the macrostructure. The stability of the stratum increased with the increase of the compactness.

Abstract:To improve the calculation accuracy and speed for 2D transient eddy current field, a method (ES-FEM-BEM) combining edge smoothed finite element method (ES-FEM) and boundary element method (BEM) is proposed in this paper. The method integrates the advantages of ES-FEM and BEM, which has high calculation accuracy and uses less memory. Compared with the traditional FEM-BEM coupling algorithm, ES-FEM-BEM has obvious advantages in improving calculation accuracy with the same meshing density. A 2D impulse coil-aluminum plate model was established, and the magnetic field strength of the aluminum plate surface was calculated. Results show that the maximum relative error between the calculated results obtained by ES-FEM-BEM and the measured results was only 3.4%, whereas the maximum relative error between the calculated results obtained by FEM-BEM and the measured results was up to 31.8%. The proposed method can provide reference for the analysis of transient open boundary eddy current field.

Abstract:Strength nonlinearity and failure modes are considered to have impact on the stability of shallow expansive soil slopes at low stresses. Based on the nonlinear characteristics of shear strength of saturated remolded expansive soil in low stress section obtained from slow shear test, the stress threshold for linear development at normal stresses and nonlinear variation at low stresses was determined by adopting the Chauvenet criterion. It was clarified that rain infiltration was the main reason that the strength of shallow sliding bodies of expansive soil slope was in the nonlinear section at low stresses. On the basis of the failure mode of “parallel slope-curve”, a stability analysis method was established to investigate the nonlinear strength characteristics of expansive soil in shallow embankment slopes at low stresses under seepage force. Results show that the mechanical properties of small cohesion and large internal friction angle of saturated expansive soil in embankment slopes at low stresses were the strength conditions of the sliding failure induced by heavy rainfall. The composite failure mode of “parallel slope-curve” based on the strength nonlinear power function model at low stresses could describe the shallow stability of expansive soil slopes more accurately, and the obtained safety factor was obviously lower than that of the circular failure mode based on the Coulomb model at normal stresses.

Abstract:To analyze the stability of traffic flow mixed with manned vehicles as well as connected and autonomous vehicles (CAV), a theory analysis method was proposed. The car-following models were linearized by using Taylor formula. The transfer function theory was used to derive the stability criterion of mixed traffic flow with different CAV proportions. Meanwhile, parametric sensitivity analysis was conducted on acceleration feedback coefficient of CAV. Considering the propagation characteristics of small disturbances under open boundary conditions, numerical simulation experiments on the stability of mixed traffic flow were designed. Research results show that the unstable speed range of CAV was within the unstable speed range of manned vehicles. The increase of CAV proportion was helpful to transform the traffic flow from unstable state to stable state. The larger the acceleration feedback coefficient of CAV was, the larger the stability regions of the mixed traffic flow with respect to CAV proportion and equilibrium speed would be. When the CAV proportion increased to 23%, the mixed traffic flow was stable within full equilibrium speeds. The research findings can theoretically calculate stability regions of CAV mixed traffic flow, and can provide evidence for analyzing stability of mixed traffic flow from the perspectives of CAV proportions and equilibrium speeds.

Abstract:The existing theory on fatigue equivalent temperature of asphalt pavement does not take account of the nonuniform traffic volume distribution and the values of asphalt pavement temperature are unreasonable. To calculate the equivalent temperature in a more accurate and scientific way, the concepts of equivalent temperature and depth of asphalt layer were proposed and corresponding calculation methods were deduced. The relationship between the daily equivalent temperature of atmosphere and the equivalent temperature of asphalt layer was established. Taking the equivalent temperature at the equivalent depth of the asphalt layer as the representative temperature and dividing the temperature into different ranges, the dynamic modulus and fatigue tests on asphalt mixtures were carried out, and the frequency of traffic volume distribution in different temperature ranges was classified. Based on the Miner linear cumulative principle, a method was proposed for calculating fatigue equivalent temperature of asphalt pavement that takes the nonuniform distribution of traffic volume into consideration. The equivalent temperature values of two traffic volume distribution modes were calculated and comparative analysis was carried out. Results show that the equivalent temperature of asphalt layer could be used as representative temperature to divide temperature ranges. The proposed calculation method for the fatigue equivalent temperature of asphalt pavement could overcome the shortcomings of the existing methods theoretically by taking the nonuniform distribution of traffic volume into consideration, which makes the calculation of equivalent temperature more scientific and reliable. The calculated temperature of two traffic volume distributions had a difference of 1.6 °C. Compared with other methods, the proposed method had certain advantages. To further improve the accuracy of the calculation method, more intensified observation should be made in the future.

Abstract:To conveniently calculate the tension force of each suspension cable of self-anchored suspension bridge during system transformation in design phase, a practical calculation method was proposed based on the internal force state of main cable. The main cable was divided into tension section and free suspension section according to the tension degree of the suspension cable. Based on the idea of displacement method in structural mechanics, the internal force of main cable tension section was made consistent with that of target state by adding restraints at the corresponding suspension points of main cable. Then the free deformation of each main cable segment was balanced by releasing the restraints to obtain the main cable state under this condition. Considering the energy conservation of each main cable segment before and after restraint release as well as the deformation compatibility conditions of the main cable, the equilibrium equation of the main cable was established and solved to obtain the internal forces of each main cable segment after system transformation. Next, according to the vertical unbalanced force between the main cable segments of the self-anchored suspension bridge, the cable forces under this condition were calculated. By comparing with the test results in engineering examples, it shows that the proposed method is convenient and concise, which is independent of the effect state of the former stage. The calculation results of the proposed method met the accuracy requirements, which can be applied in the system transformation analysis and structural design analysis of general self-anchored suspension bridges and might be the guidance for structural design and optimization.

Abstract:To study the creep properties of the adhesive of carbon fiber reinforced polymer (CFRP)-steel interface, long-term loading tests of CFRP-steel double-lap specimens were carried out under different tensile loads, and the strain distribution law of CFRP and its changing characteristics with loading time were analyzed. Based on the characteristics of the Burgers model and the time-varying law of the shear strain of adhesive layer, a solving method for each parameter in the model was given. According to the experimental data, the expressions of the parameters in the Burgers model and the Findley power law equation were obtained. Results show that under the action of long-term interfacial shear stress, the adhesive of CFRP-steel interface had creep deformation, and the strain of CFRP decreased nonlinearly from loading end to fixed end, which increased with the increase of loading time and the increasing rate decreased gradually. The higher the value of interfacial nominal shear stress was, the larger the creep deformation of adhesive was, and the more the strain of CFRP increased. In the Burgers model, parameters η_M and G_K were both linear functions of shear stress τ, and parameter η_K was a quadratic function of shear stress τ. In the Findley power law equation, parameter m was a linear function of shear stress τ, and parameter n was a quadratic function of shear stress τ. The root mean square errors of the Burgers model and the Findley power law equation were small, and both models could predict the creep deformation of the adhesive. When the interfacial shear stress τ was high, the creep deformation predicted by the Burgers model was better than that predicted by the Findley power law equation.

Abstract:To reduce the probability of roadside accidents in small curve sections of highways, eight roadside accident risk factors including road geometric design indexes (horizontal curve radius, hard shoulder width, longitudinal slope, superelevation slope, and widen value of curve), pavement condition (adhesion coefficient), and traffic characteristics (running speed and vehicle type) were chosen to carry out PC-crash simulation test, and a total of 12 800 accident data sets were collected. Chi-squared automatic interaction detection (CHAID) decision tree technique was employed to identify significant risk factors, and the comprehensive influence of the interaction of various factors on roadside accidents was discussed. These factors were then chosen as predictors of probability of roadside accidents in Bayesian network analysis to establish the probabilistic prediction model of roadside accidents. Finally, according to probabilistic prediction results, the identification method for roadside accidents black spots was proposed and verified through tests. Results show that running speed had the greatest effect on the occurrence of roadside accidents, followed by horizontal curve radius, vehicle type, adhesion coefficient, and hard shoulder width. When 80 km/h

Abstract:In order to study the effect of elastoplastic deformation on the corrosion electric field of ships, a mechanochemical coupling model of corrosion electric field was established by using the solid mechanics and the secondary current distribution modules in the COMSOL simulation software based on the corrosion defect of ship hull surface. Two physical fields were solved by using the sequential solver setup, and the structural stress-strain simulated by the solid mechanics module was coupled to the expressions of equilibrium potential and exchange current density of electrode reaction, which were taken as the boundary conditions of the secondary current distribution module. Results show that the deformation of the hull structure caused the stress concentration at the corrosion defect, and the metal corrosion potential shifted negatively due to the mechanochemical effect. The existence of potential gradient in solution provided driving force for the current flow, thus forming the stress corrosion couple. Moreover, the center of the defect was anode and both sides of the defect were cathodes. When the corrosion defect was elastically deformed, the modulus of corrosion electric field generated by stress corrosion couple was small, while the corrosion electric field increased significantly when the corrosion defect was plastically deformed.

Abstract:To tackle the problem of attitude synchronization control of satellite formation under angular velocity constraint, a comprehensive design strategy of additional system dynamic-attitude synchronization controller was proposed. Firstly, considering the influence of angular velocity constraint, a spacecraft formation model was established. Then, an attitude tracking error equation was established. The angular velocity constraint was converted into angular velocity tracking error constraint, and a new finite-time additional system dynamic was designed to ensure that the attitude change met the constraint requirements. Next, based on the state of the additional system, an attitude synchronization controller was designed to realize the finite-time attitude synchronization of satellite formation. Finally, a distributed real-time simulation verification platform was built. The main control unit extracted real-time data from the simulation unit to draw a simulation curve, and sent the data to the visual unit for scene driving. Through the comparative analysis of the real-time simulation curve and the offline simulation results, as well as the three-dimensional visualization demonstration of the formation control process, the reliability verification of the control algorithm in real-time environment was realized.