Abstract:To investigate the shear performance of sleeved stud connectors， 8 stud push-out specimens were designed， and static loading tests were conducted to evaluate the mechanical performance. The shear performance differences between the novel sleeved studs and conventional welded studs were compared. Referring to the experimental results， an Abaqus nonlinear finite element model was developed to study the shear mechanism of sleeved stud connectors. The experimental results indicated that the ultimate shear bearing capacity and shear stiffness of the sleeved stud connectors are higher than those of ordinary welded studs， and the maximum slip is relatively small. Compared to conventional welded studs， the ultimate bearing capacity of sleeved studs increases by 4 % to 8 %， and the shear stiffness increases by 25 % to 35 %. Finite element analysis shows that the shear failure process of sleeved stud connector is similar to novel sleeved stud connector， but the failure range and stud stress of sleeved stud connector is smaller than that of novel sleeved stud connector. The concrete failure of the sleeved stud connector occurs inside the sleeve， while the concrete outside the sleeve is not damaged. Experimental and numerical analysis have shown that the mechanical properties of the sleeved stud connector are better than those of novel sleeved stud connector. It is feasible to design and calculate sleeved stud connector according to the method of novel sleeved stud connector.

Abstract:Currently， when prefabricating reinforced concrete composite beams in factories， the upper longitudinal bars are typically not directly tied into the rebar cage. Instead， the upper longitudinal bars are passed through the cage and tied on-site， which makes the construction process more difficult and less efficient. To address this issue， this paper proposed a connection design where the upper longitudinal bars were directly placed above the hoop and tied. Two types of hoops were designed： one with a groove and one without. Bending tests were conducted on cast-in-place beams， traditional prefabricated composite beams， and the novel prefabricated composite beams with externally placed upper longitudinal bars， all of which had identical dimensions， concrete grades， and reinforcement configurations. Numerical simulations of the tests were performed using ABAQUS software to investigate the influence of the new tying method on the mechanical properties of the beams. The results indicate that the novel prefabricated composite beams exhibit similar load-bearing capacity to traditional prefabricated composite beams， slightly lower than that of cast-in-place beams. This suggests that the proposed method of tying the upper longitudinal bars is safe and reliable， with promising potential for practical application in engineering.

Abstract:In this paper， based on the proposed scrap tire pads， the horizontal mechanical properties tests and finite element analysis are conducted under the design compressive stresses of P=3 MPa， P=4 MPa， and P=5 MPa， to analyze the laws of the changes of the horizontal equivalent stiffness， post-yield stiffness and the equivalent damping ratio with the design compressive stresses and the second shape coefficients， and to determine the specific methods of the values of the three. Horizontal mechanical properties test results show that： the horizontal equivalent stiffness and post-yield stiffness of layer-bonded scrap tire rubber pads（LBSTP） increase with the increase of the design compressive stress and the second shape coefficient， and the existence of the lower limit values of the two can be determined to be 0.5 kN·mm^-1 and 0.37 kN·mm^-1， respectively. Meanwhile， the values of the two show the law of fan distribution. The variation of the equivalent damping ratio has no obvious relationship with the design compressive stress and the second shape factor， but its value can be determined as between 0.09 and 0.15. According to the value law of horizontal equivalent stiffness and post-yield stiffness of LBSTP， the finite element model of LBSTP is developed using ABAQUS， and the calculation formula for the sector of value taken by horizontal equivalent stiffness and post-yield stiffness is established for the LBSTP.

Abstract:To investigate the effects of the upper limit stress ratio on the fatigue damage mechanics of potassic granite， uniaxial compression tests and constant amplitude cyclic loading tests with four upper limit stress ratios （0.75， 0.80， 0.85， 0.90） were conducted. Based on the experimental data， the stress-strain curves， fatigue life， fatigue limit strain ratio， as well as the macroscopic and microscopic evolution pattern of granite failure characteristics were summarized and analyzed. Based on the hysteresis curves during cyclic loading， key parameters such as dynamic modulus， damping ratio， dynamic Poisson’s ratio， and cumulative residual strain were calculated. Additionally， a damage value computation method based on average residual strain was proposed to describe the deformation and failure process of the rock sample. The results indicate the presence of a dilatancy stress ratio. When the upper limit stress ratio exceeds this threshold， the samples undergo fatigue failure， and the fatigue life decreases as the upper limit stress ratio increases. The axial deformation during fatigue failure is governed by the evolution of the uniaxial static stress-strain curve. Macroscopically， the extent of damage in the samples increases with the upper limit stress ratio， while microscopically， the complexity of fracture morphology also intensifies. The dynamic elastic modulus and Poisson’s ratio during fatigue failure exhibit a two-stage variation trend， while the damping ratio and residual strain show a three-stage varying feature. The fatigue damage values， calculated using the average residual strain method， exhibit a three-stage “inverse ‘S-shaped’” evolution pattern as the number of cycles increases. Finally， a low-cycle fatigue damage model was introduced to describe the fatigue damage pattern， whose predictive performance was satisfactory according to the comparison with experimental data.

Abstract:To address the thermal-mechanical behaviors of geotechnical media in engineering including energy piles and geothermal power generation， the governing equations covering the anisotropy of moduli， linear thermal expansion coefficients and thermal conductivity are introduced. Then， the partial differential equations are discretized along depth and time domain based on the discretization rules of the transformed differential quadrature method （TDQM）. Various load forms of mechanical loads， heat sources and temperature loads are considered， and the coupled thermal-mechanical solution is obtained after introducing the internal continuity conditions and boundary conditions. The proposed theory is verified through case studies. Finally， a sensitivity analysis is performed to provide a basis for the analysis of thermal-mechanical coupling behavior of layered cross-anisotropic media.

Abstract:A novel approach for slope reliability assessment considering uncertainty associated with rainfall intensity temporal patterns is proposed. Stochastic rainfall sequences considering rainfall intensity temporal patterns are generated based on skewness and kurtosis. These series are incorporated into a coupled seepage–stability model of slope， and Monte Carlo simulation is employed to estimate slope failure probability. The proposed approach is applied to a conceptual slope in Zhejiang Province to evaluate the impact of rainfall intensity time patterns on slope failure probability and failure time. The results show that， under the same total rainfall and duration， early-peaking and relatively uniform rainfall patterns lead to greater infiltration， reduce soil strength， and thus increase the likelihood of slope failure while shortening the time to failure. These findings highlight the importance of incorporating rainfall intensity temporal patterns in landslide early warning systems.

Abstract:Non-aqueous phase liquids （NAPL） have very low dielectric constant. Therefore， they can affect the electric double layer， as well as the physical and mechanical characteristics of clay. NAPL contamination has been frequently discovered in the coastal saturated clays formed during the Holocene transgression. To investigate the impact of NAPLs on soil structure and the contaminant transport in these coastal saturated clays， long-term soaking tests （up to 1.8 years） were conducted on intact saturated Shanghai clays （primarily composed of illite） using three NAPLs： kerosene， trichloroethylene （TCE） and kerosene-ethanol mixture. The results were also compared with those obtained from bentonite （primarily composed of smectite）. Test results shown that under the long-term action of NAPLs， the Shanghai saturate clay exhibited shrinkage， cracking， and flocculation， but significantly less pronounced than in bentonite. The intensity of structural alteration follows the order of kerosenekerosene-ethanol mixtureTCE. Except for the dielectric constant of NAPL， the velocity and amount of the free-phase NAPL infiltrating in the soil are also important factors influencing the structural alteration. Under the coupled impacts of shrinkage （decreasing in void ratio） and flocculation （decreasing in specific surface）， the hydraulic conductivities of the Shanghai saturate clays are found to increase by up to two times.

Abstract:The current classification methods for highway entrance ramp merging behavior are limited to single and isolated driving scenarios， without considering the dynamic changes in the spatial and temporal positions of merging vehicles and surrounding vehicles in the target lane， neglecting the study of bidirectional and multi-interaction merging scenarios， which poses significant challenges for researchers in understanding real traffic flow characteristics and developing automated driving systems with lane-changing algorithms. To reveal the dynamic interactive behavior among vehicles during actual merging processes， this paper， combining the ExiD dataset with high-definition map data to extract natural driving merging trajectory data， proposes a merging scenario classification method that fully considers the spatiotemporal dynamic changes. Additionally， it utilizes the Jensen-Shannon divergence to construct a quantitative model and index for measuring scenario similarity， representing the differences and similarities among different merging scenarios. The results show that， after considering the spatiotemporal distribution of surrounding vehicles in the target lane， the merging behavior on the ramp can be divided into eight distinct scenarios with significant differences， including scenarios with higher risks， such as parallel vehicles （average time-to-collision 2 s）. These findings are of great importance in analyzing high-risk merging scenarios and designing automated merging strategies that align with the interaction characteristics of human drivers.

Abstract:Autonomous vehicles need to perceive constantly changing road alignments， section characteristics， and environmental factors when driving on mountainous freeways， and analyze safe driving boundaries. This paper focuses on testing the lane detection performance of autonomous vehicles based on LiDAR in mountainous freeway environments and analyzes the influencing factors of lane perception failure. Using the Road and Traffic Holographic Data Acquisition System of Tongji University， the on-road vehicle test was conducted on the Guidu freeway in Guizhou Province， with multiple round trips totaling 3 200 kilometers. The impact of 11 feature variables on perceived failure was explained based on the CatBoost model and Shapley Additive exPlanations （SHAP）. The research results indicate that weather factors have the most significant impact on the perception failure of lane markings， followed by the influence of road alignments. Specifically， a higher probability of perceptual failure will be detected when there are the following characteristics： larger maximum curvature， larger grade change rate， exit， and entrance sections， longitudinal deceleration markings， lateral deceleration markings， higher driving speed， etc. The results of this paper can not only provide measures more suitable for the safe operation of autonomous driving on mountainous highways， adapting better to autonomous vehicles， but can also serve as a reference for establishing the operational design domain for autonomous driving.

Abstract:This paper focuses on the method of combining traffic safety facilities in long tunnels， aiming to determine the optimal combination form and quantity to enhance driving safety within tunnels. Six common traffic safety facilities， which are not fully specified under current standards， were selected and combined into six schemes based on the scheme complexity and spatial location. Based on driving simulation experiments， repeated measures variance analysis was conducted to explore the differences in each driving behavior indicator under different schemes. A multi-index fuzzy comprehensive evaluation model was developed to evaluate the performance of different combination schemes. The results show that appropriate combinations of traffic safety facilities can enhance the stability of driverss’ control in long tunnels. The combination scheme of “road studs + facade markings + contour marks + double waist lines”can enhance drivers’ perception of road rights within the tunnel. However， excessive accumulation or setting multiple types of traffic safety facilities at the same location does not consistently improve tunnel driving safety.

Abstract:Changes in traffic flow structure and the increase in traffic volume have created an urgent need for the analysis and exploration of the utilization of throughput capacity of large high-speed railway passenger stations. For high-speed railway stations in China， the adoption of the route-lock-section-release mechanism based on centralized traffic control （CTC） system offers potential for further enhancing the throughput capacity of stations， compared to the conventional route-lock-route-release mechanism. A simulation model for the throughput capacity of stations is established， with station infrastructure layout as the underlying data and train working diagram as the input condition. Based on the CTC performance mechanism， the model first analyzes the operation process of a single train in the station， as well as the interactions between multiple trains to determine the relevant time parameters of trains in the station， calculates the capacity utilization rate of traffic facilities such as switches and tracks， identifies key facilities that limit the capacity， computes and outputs the throughput capacity of stations. The results show that compared with the traditional throughput capacity calculation method， the computer simulation method can simulate the route-lock-section-release mechanism in a more microscopic way. This method can analyze the related factors and calculate the throughput capacity in detail， which is helpful to support the optimization of facility upgrading and station operation plan from the perspective of the overall improvement of the throughput capacity of stations.

Abstract:To evaluate the suitability of multi-source crumb rubber powder for asphalt modification rubber powders derived from radial tires， nylon tires， passenger car tires， tire bead， rubber hoses， and conveyor belts were selected to analyze its composition， functional group distribution， microscopic morphology， and elemental composition. Furthermore， the properties of single rubber powder， rubber powder-SBS composite modified asphalt， and their mixtures were studied. The results indicated that rubber powders from passenger car tires and nylon tires exhibit similar microstructures and macroscopic properties to those from radial tires， making them high-quality modifiers for asphalt. However， rubber powders from tire bead， rubber hoses， and conveyor belts are not suitable for direct use in asphalt modification and require composite modification. Based on these findings， and in conjunction with the existing classification standards for rubber powders， a technical standard for the classification of rubber powders based on road performance was proposed.

Abstract:To investigate the relationship between the magnetic field response above the rail surface and the spatial morphology of rolling contact fatigue （RCF） crack on the rail surface in alternative current field measurement （ACFM）， the surface opening length， internal angle， and ellipse ratio range of RCF crack under different gross passing loads were determined by combining field visual observation， metallographic observation， and computer tomography（CT） scanning of rail with RCF crack. An ACFM simulation model for rail crack was developed to analyze the ACFM response of different crack morphology parameters， and the magnetic field response was fitted to express the crack spatial morphology parameters. The results show that the ACFM response of RCF crack is comprehensively affected by each semi-elliptic parameter of the crack and can be described by the function model. The determination coefficient of the description function is greater than 0.999 8， the sum of squares error is below 1×10^-4， and the mean square error is less than 1.4×10^-3. The calculated results of the function model are in good agreement with the ACFM response. Overall， the ACFM response characteristics are less affected by the internal angle， but the influence gradually increases as the internal angle decreases. The ACFM response characteristics vary linearly with the crack surface opening length， and exponentially or as a higher order multinomial function with the elliptic ratio.

Abstract:The variation law of dynamic mechanical performance parameters of rubber was analyzed through accelerated aging test and dynamic mechanical performance evaluations. The parameters of viscoelastic constitutive model of rubber were obtained by non-linear least squares fitting. A method for calculating the three-dimensional dynamic stiffness of V-shaped rubber damping elements was proposed by introducing shape coefficients. Using the dynamic stiffness of rubber damping components as the aging index， a dynamic stiffness performance evolution model was developed for rubber damping components. A finite element model of the high-speed train body and under vehicle equipment， as well as a rigid flexible coupling dynamic model of the high-speed train was developed to explore the effects of external environmental temperature， excitation frequency， and thermal oxygen aging on modal frequency， coupled vibration of the body and under vehicle equipment. The results show that the low-order modal frequencies will increase to varying degrees with the increase of dynamic stiffness. The impact on first-order low-frequency vertical bending and first-order high-frequency vertical bending is more significant. When the dynamic stiffness value of the damping element increases， the first-order low-frequency vertical bending mode frequency approaches the first-order vertical bending frequency without the suspended equipment， and its corresponding amplitude increases. The first-order high-frequency vertical bending mode frequency shifts towards higher frequencies， and its corresponding amplitude decreases. The research results can provide reference for the engineering application of rubber vibration isolation components in high-speed trains.

Abstract:The traditional insurance market finds it difficult to cover the loss caused by massive claims resulting from catastrophe. Insurance companies can issue catastrophe bonds to transfer part of the catastrophe risk to the capital market thereby alleviating claims pressure through risk diversification. This paper considers the pricing of a class of catastrophe bond that makes payments based on the degree of loss. Using a nonhomogeneous compound Poisson distribution to model the cumulative catastrophic losses， it derives the coupon payment process and the proportion of principal repaid at maturity. It obtains an expression for the catastrophe bond pricing under the risk-neutral measure， and conducts numerical simulations to analyze the results. The findings show that the higher the preset loss threshold for triggering claims， the lower the probability of triggering and the smaller the payment ratio. However， the discounted value of the catastrophe bond increases..

Abstract:This paper， from the perspective of component suppliers， investigates integrated production-transport scheduling of prefabricated construction under uncertainty. A bi-level optimization model， considering cost and satisfaction objectives， is developed to describe the uncertainty of component production processing time， transport time， and installation time windows with fuzzy numbers. In the upper-level model， a genetic algorithm （GA） is employed to determine the optimal order allocation among production lines to minimize the total production-transportation costs. In the lower-level model， the adaptive greedy tabu genetic algorithm （AGTGA） is proposed to optimize the integrated production-transportation scheduling on a single pipeline production-transportation integrated scheduling to maximize satisfaction based on fuzzy pessimistic criteria. Besides， an iterative process achieves optimal scheduling solutions under uncertainty by exchanging solutions between the upper and lower levels. The results indicate that AGTGA outperforms iterated greedy algorithm （IGA） and GA， achieving optimal objectives of upper and lower models under uncertainty and determining the optimal solution for production-transport integrated scheduling of prefabricated buildings.