Journal of Chongqing Jiaotong University(Natural Science)

Experimental Study on the Bonding Performance of High-Strength Steel Bar and UHPC Interface

WAN Jiakai1, MA Licheng2, TIAN Zhidian1, CHENG Xiaoliang1, ZHANG Haojun1, ZHU Aizhu2

2026, 45(2): 1-7. DOI: 10.3969/j.issn.1674-0696.2026.02.01

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Through the experiment of 32 pull-out specimens with HRB600 high-strength steel bars and ultra-high performance concrete (UHPC), the influence of steel bar diameter, anchorage length and relative cover layer thickness on the interfacial bond performance was systematically analyzed, and the methods for calculating the critical anchorage length and bond strength were proposed. The research results indicate that the test specimens mainly exhibit three failure modes: unyielding pullout of the steel bar, yielding pullout of the steel bar, and breakage of the steel bar. When the relative cover layer thickness is constant and the steel bar diameter is 12mm, the anchorage length is increased from 48mm to 72mm, leading to an approximate increase of 94.1% in pull-out resistance and an improvement of 29.4% in bond strength. When the relative anchorage length remains the same and the relative cover layer thickness is about 3, the steel bar diameter is increased from 14 mm to 22 mm, and the pull-out resistance is improved approximately 158%. The lower limit of the critical anchorage length between high-strength steel bars and UHPC is found to be 5 times the diameter of the steel bar, and it tends to decrease as the diameter increases. It is recommended that the designed anchorage length should not be less than 10 times the diameter of the steel bar. Based on the statistical analysis of 41 sets of pull-out test data, a formula for calculating bond strength is established, which exhibits minor errors and is suitable for estimating the bond strength between high-strength steel bars and UHPC within the specified parameter range. Furthermore, when the bonding area remains relatively constant, appropriately increasing the thickness of the relative cover layer can help to enhance the bond strength.

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Experiment of Rockfall Impact on Rubber Particle Buffer Cushion Layer and SPH-FEM Simulation

WANG Xing 1,2,3, NIE Yawei 1,2, HUANG Shuai 1,2, MEI Hua 4, HU Zhaoxia 4

2026, 45(2): 8-13. DOI: 10.3969/j.issn.1674-0696.2026.02.02

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To investigate the rockfall impact resistance characteristics of shed tunnels with rubber particle cushions, similar model tests of shed tunnels with sand cushion and rubber particle cushion, as well as SPH-FEM coupled numerical simulation work, were carried out respectively. The mechanical response characteristics of shed roof and column structures under rockfall impact were explored. The research results demonstrate that the rubber particle cushion exhibits superior performance in inhibiting stress propagation. Compared to sand cushion, the peak strain values at the longitudinal N1 and transverse M1 positions of the shed roof with rubber particle cushion decreases by 28.54% and 30.02% respectively, while the peak compressive strain of the columns decreases by 65.47%. The numerical calculation results of the shed tunnel with actual on-site dimensions indicate that the reduction range of the peak stress is between 32.62% and 42.47% at the longitudinal N1~N4 positions and between 9.04% and 56.82% at the transverse M1~M6 positions of the shed roof with rubber particle cushion. The peak displacement reduction of the top plate web is 6.20%, the compressive stress reduction of the column is 36.61%, and the rockfall impact acceleration reduction can reach 34.91%. The rubber particle buffer cushion layer has obvious energy dissipation and shock absorption effects.

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Evaluation of Airport Rigid Pavement Grades and Parameter Sensitivity

LI Longhai, WU Siming

2026, 45(2): 14-23. DOI: 10.3969/j.issn.1674-0696.2026.02.03

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The development trend towards larger aircraft and more complex load spectra directly links the evaluation accuracy of the load-bearing capacity of airport rigid pavements to flight safety and runway service life. The traditional CAN-PCN method exhibits limitations in aspects such as characterizing the time-varying effects of dynamic loads, nonlinear cumulative damage and the interlayer response of composite pavements. In response, the International Civil Aviation Organization (ICAO) has promulgated the ACR-PCR method based on the fatigue damage mechanism. Through empirical analysis, the key factors influencing the pavement classification rating (PCR) RPC and their mechanisms of action were systematically investigated. Based on layered elastic analysis (LEA) model and the cumulative damage factor (CDF) model, the parametric sensitivity analysis and case validation were conducted on a 4C-grade airport pavement by combining with CAAC-PCR software. The research results indicate that the surface layer thickness and flexural strength exert the most significant influence on RPC. A 10% increase in thickness elevates the RPC by 8%~12%, while an increase in flexural strength from 4.5 MPa to 6.0 MPa results in a remarkable RPC increase of 53%. A critical threshold exists for the reaction modulus of the subgrade top surface, beyond which RPC tends to stabilize. Under the action of the mixed aircraft fleet loading, the contribution rate of wide-bodied aircraft to the critical damage area of the runway surface is as high as 76.8%. This research provides a quantitative basis for the accurate evaluation of the load-bearing capacity of rigid airport pavements, thereby enhancing the scientific nature and engineering applicability of the assessment method.

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Evaluation of Crack Resistance of Multi-source Oil Rejuvenated Asphalts Based on Optimized Parameters

LING Tianqing1, WEI Qiao1,2,3, YUAN Ying1

2026, 45(2): 24-30. DOI: 10.3969/j.issn.1674-0696.2026.02.04

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To investigate the effectiveness of performance testing procedures and technical parameters for rejuvenated asphalts, fatigue performance and low-temperature cracking resistance recovery was taken as the research objective, and the wide-temperature-range rheological test, low-temperature creep test, and ductile cracking failure tests were conducted. Cracking parameters, including intermediate continuous grading temperature (TICG), Glover-Rowe parameter (PG-R), limiting phase angle temperature (T30°, T45°, ΔTcδ), low-temperature continuous grading temperature (1 h TCLG, 72 h TCLG), grade loss (LG), and critical tip opening displacement (DCTO), were selected to investigate the impact of multi-source oil rejuvenators (AAS, Cargill, Cyclogen, REOB) and their dosages (2%, 4%, 8%) on the crack resistance of rejuvenated asphalt. Pearson correlation analysis was used to assess the effectiveness of different cracking parameters, and the optimal dosage ranges for rejuvenators were determined on the basis of the preferred parameters. The results indicate that chemical aging is an irreversible process. The parameters related to gelation, ΔTcδ and DCTO, exhibit a slow trend or almost no change with increasing rejuvenator dosage. Limiting phase angle temperature is a potential effective indicator for evaluating the thermal cracking resistance of asphalt binders, which can be obtained through a relatively simple testing procedure. The lower limit of rejuvenator dosage was determined on the basis of the limiting phase angle temperature, whose value closely aligns with the actual amount in engineering. Compared to TICG, PG-R is a better option for assessing the cracking of aged/rejuvenated asphalts. According to the preferred parameters, the regeneration efficiency ranking and dosage range for the three selected commodity rejuvenators are determined as follows: Cargill (3.4%~8.9%) > AAS (6.5%~15.6%) > Cyclogen (10.5%~18.4%).

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Intelligent Detection of Asphalt Pavement Wear Based on Terrain Prominence

CHEN Hua，BAI Jiayu，LYU Yuejing

2026, 45(2): 31-38. DOI: 10.3969/j.issn.1674-0696.2026.02.05

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In the evaluation of pavement wear detection, the traditional sand patch method and drainage method for measuring pavement texture depth are inefficient and susceptible to human factors. Although the laser cross-section detection equipment offers fast detection speed, it is influenced by the position of the longitudinal measurement line and the pavement alignment, leading to errors in DMP, RW, and PWI, which affects the reliability of the wear evaluation results. In order to accurately evaluate and quickly detect pavement wear, a method that utilized terrain prominence as a wear indicator for grade judgment and employed the ResNet50 model for image classification of pavement wear was proposed. Images and 3D texture data of roads with the same pavement type but different operation years were collected, and terrain prominence was determined as the evaluation index to judge the wear grade of the images. Then, the ResNet50 convolutional neural network was used as the initial training model, and a transfer learning strategy was adopted to fine-tune the model parameters, thereby improving the training speed and classification accuracy of the model. The research results show that the terrain prominence index can well reflect the pavement wear condition, and the average accuracy of the pavement wear detection model based on ResNet50 can reach 98.49%. By deploying the proposed model on mobile devices, the developed pavement wear detection APP can be run on any Android-system-based mobile phone, meeting practical application needs and achieving rapid and accurate detection of pavement wear.

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Effect of Rejuvenator on the Rheological Properties and Anti-aging Performance of Aged Asphalt

LI Ping1，ZHANG Liubo1，BAI Zhongliang1，LI Wei1, ZHANG Qiang2

2026, 45(2): 39-46. DOI: 10.3969/j.issn.1674-0696.2026.02.06

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Recycled asphalt technology is a crucial means to enhance the utilization rate of waste asphalt mixture and achieve sustainable development in asphalt road construction. However, due to the high degree of aging of old asphalt, its performance after regeneration with ordinary rejuvenator often fails to meet the demands of long-term use. To address this issue, taking recycled asphalt as the research object, the physical indicators, rheological properties, component content, molecular weight distribution and absorbance of asphalt before and after recycling were comparatively analyzed, through conventional tests, dynamic shear rheological (DSR) test, bending beam rheological (BBR) test, SARA test, gel permeation chromatography (GPC) test and ultraviolet-visible absorption spectrum (UV-Vis) test. The results show that: after short-term and long-term aging of asphalt, the rheological properties and microscopic indicators of the recycled asphalt are closest to those of matrix asphalt when the amount of rejuvenator is 4%~6% and 12%~14%, respectively. The aging process will lead to an increase in the proportion of components with larger molecular weights in the asphalt, and the regenerant will restore the performance by increasing the proportion of components with smaller molecular weights in the recycled asphalt. Compared to the aged asphalt, the residual penetration and residual ductility ratio of recycled asphalt increase, the increment of softening point decreases, and the absorbance index is greater than that of aged asphalt and original asphalt. The anti-aging performance of recycled asphalt is close to that of original asphalt. The residual penetration, residual ductility ratio, softening point increment and absorbance can be used as indicators to evaluate the anti-aging performance of recycled asphalt.

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Road State Recognition Clustering Algorithm Based on Improved Particle Swarm Optimization and K-means

XU Tao1,2, REN Qiliang1, LI Jinyan3, LIN Wei1

2026, 45(2): 47-56. DOI: 10.3969/j.issn.1674-0696.2026.02.07

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To address the problem of fluctuation in clustering accuracy caused by the influence of initial clustering centers in traditional K-means algorithm, a combined clustering algorithm based on improved particle swarm optimization (PSO) was proposed. Firstly, based on the one-dimensional raw data of road operating velocity, two features, including relative velocity ratio (αt) and velocity fluctuation rate (βt), were added to establish a new three-dimensional dataset. Secondly, based on the randomized delayed distributed particle swarm optimization (RODDPSO), an improved RODDPSO algorithm (IRODDPSO algorithm) was proposed, in which a nonlinear constraint function for the maximum particle velocity was introduced. As the number of iterations increased, the maximum update speed of particles gradually decayed nonlinearly. According to the evolutionary characteristic value ξ of each iteration round, different particle update strategies were determined. Finally, the IRODDPSO algorithm was utilized to generate the initialized clustering centers for K-means, and the global search capability of the PSO algorithm was used to find the optimally initialized clustering centers. The research results show that the IRODDPSO algorithm can be successfully applied to clustering analysis of urban road operating conditions. The accuracy and recall rates of the combined algorithm were 0.935 and 0.957, respectively, which were 4.8% and 3.6% higher than that of the RODDPSO algorithm and 13.2% and 11.1% higher than that the benchmark PSO algorithm. The running time consumption of the combined algorithm decreases by 6.7% and 16.3% respectively, compared to the above two algorithms. The proposed maximum speed nonlinear constraint strategy enhances the convergence ability of the algorithm and demonstrates good robust on different levels of roads, including expressways and arterial roads.

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Traffic Flow Prediction Based on Dynamic Graph Neural Delay Differential Equations

LAN Li， ZHAO Xin

2026, 45(2): 57-65. DOI: 10.3969/j.issn.1674-0696.2026.02.08

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Aiming at the problems of delayed traffic flow effects between upstream and downstream of road sections and insufficient excavation of spatio-temporal correlation characteristics among intersections in the existing research on urban road traffic flow prediction, a model based on dynamic graph neural delay differential equations was proposed to fine-grain the instantaneous changes of traffic flow and extract long-distance dynamic spatio-temporal features in order to improve the prediction accuracy. Firstly, considering that the traffic flow showed high similarity at different cycle scales, the spatio-temporal attention mechanism was used to model the weekly and daily scale traffic flow data to enhance the spatio-temporal correlation among intersection nodes. Secondly, the delay time between upstream and downstream roads was calculated and delay differential equations were introduced to extract the time lag characteristics among nodes of the road network, simulating the spatial information propagation process under the delay effect. Finally, the features of each time scale were integrated to obtain the predicted output values. Through the validation of real public traffic flow datasets such as PEMS04, PEMS07 and PEMS08, the results show that the average absolute error and the root mean square error of the proposed model are reduced by about 2.20% and 1.16% on average.

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Comprehensive Spatiotemporal Effect Analysis on the Severity of Motorcycle Accidents without Helmets

PAN Yiyong1, MIAO Jialin1, ZHAO Kailong2

2026, 45(2): 66-75. DOI: 10.3969/j.issn.1674-0696.2026.02.09

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Aiming at the injury severity of motorcycle crashes involving non-helmeted riders, various kinds of Bayesian spatiotemporal logistic models were established to systematically evaluate the comprehensive impact of driver, vehicle, road, and environmental characteristics. Based on relevant data from 5,447 crashes from 2 015 to 2 019, five kinds of models incorporating spatial, temporal, and spatiotemporal interaction effects were established and the Markov chain Monte Carlo method was used to carry out parameter estimation. Results show that the two-component mixed model comprehensively considering Leroux CAR spatial prior, temporal random walk, and spatio-temporal interaction effect achieves the best performance, achieving a classification accuracy of 86.74% and a 3% reduction in DIC value, which significantly outperforms other models and identifies rainfall as a significant risk factor at the first time. Further analysis reveals that older age, distracted driving, drug driving, high-speed driving, nighttime travel, and complex road conditions all significantly increase the severity of accidents, while low speed, urban roads, and certain distracted environments can mitigate risks to some extent. Research indicates that breaking through the assumption of spatial and temporal independence and introducing spatiotemporal interaction effects are of great significance for revealing complex risk patterns. The proposed model can offer a refined risk assessment tool for traffic management and provide a theoretical basis for formulating targeted safety strategies, such as strengthening education for elderly drivers and enforcing helmet wearing.

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Influencing Factors of Flight Cut-off Time at Civil Transport Airports

LI Mingjie, FENG Sirong, YIN Tiance

2026, 45(2): 76-84. DOI: 10.3969/j.issn.1674-0696.2026.02.10

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The rational setting of flight cut-off time plays a significant role in enhancing airport service efficiency and improving passengers aviation travel experience. Thereby, exploring its impact mechanism can provide a theoretical reference for airports to formulate and optimize flight cut-off time according to demand. Firstly, an influencing factor system for flight cut-off time was established, which was based on literature research and survey results that identified 15 primary influencing factors. Secondly, by combining Grey-DEMATEL-TAISM, the causality degree and centrality ranking of each influencing factor were calculated, and then two root cause key influencing factors, four sensitivity key influencing factors, and a set of key influencing factors with a mutual causal relationship were determined. The research findings indicate that passenger flow line design, departure resource allocation, flight ground support services, ground support equipment configuration, and collaborative operation levels are significant factors affecting flight cut-off time. Among these, the passenger flow line design is a strong driving factor that requires particular attention in operational management. Passenger throughput and terminal configuration, located at the bottom of the topology, serve as root influencing factors, which can be improved by methods such as reasonably predicting throughput during the early-planning stage and replacing large single-building terminals with one airport and multiple terminals. The classification of factors within the causal loop encompasses passenger flow, baggage flow and flight flow. It is essential to pay full attention to the containment relationships among these three systems and enhance airport operational efficiency through collaborative management.

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Game Analysis of Multi-modal Subsidy Strategies for New Corridors in Water Transportation Considering Synergistic Economic-Environmental Benefits

XIAO Jinfeng1, TANG Boming2,3, YU Haiyan1,4

2026, 45(2): 85-94. DOI: 10.3969/j.issn.1674-0696.2026.02.11

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In order to give full play to the economic and environmental benefits of new corridors in the water transport network, a multi-modal subsidy strategy based on transport routes or (and) ship types was proposed to study its incentive effect on the water transport market structure. Aiming at the problem of cargo source allocation among three transportation routes, namely, river-sea transit in the original channel, river-sea direct delivery in the new channel, and river-sea transit in the new channel in waterway transportation, a multi-party game model composed of carriers of the three transportation routes and the government was constructed. Considering the service quality, transportation cost, carbon emission and other factors of different routes, the Nash game and Steinberg game was used to solve the problem, and the optimal government subsidy mode and subsidy amount was determined with the goal of maximizing economic-environmental benefits. Through the case study of Pinglu Canal, the impact of different subsidy schemes on the freight rates, freight volume and the interests of various decision-making entities was analyzed. The research results show that government subsidies can help to increase the overall freight volume and reduce the freight rates, and government subsidies will increase the social welfare. When only subsidizing the ship type, the subsidy amount is the largest, the social welfare is the highest, the overall carbon emissions of the three transportation routes are the lowest, and the economic-environmental benefits are optimal.

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Measurement of Carbon Emissions from Transportation in the Pearl River Delta Region

ZHOU Zhijie1, 2, LIU Yunlong1

2026, 45(2): 95-103. DOI: 10.3969/j.issn.1674-0696.2026.02.12

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Based on statistical data from 2011 to 2020, the carbon emissions from the transportation sector in the Pearl River Delta region were measured. And the STIRPAT model was applied to predict peak carbon emissions under eight scenarios from 2021 to 2035, meanwhile, the shift-share analysis method was employed to evaluate the interregional transfer of transportation carbon emissions from 2011 to 2019. The research results show that carbon emissions from transportation sector in the Pearl River Delta region have shown a trend of initial decline followed by an increase from 2011 to 2020. Under scenarios of low economic growth and rapid development of environmental technology, carbon emissions are projected to reach their peak by 2030. Moreover, the optimization of transportation structure and energy structure has an inhibitory effect on carbon emissions. From 2011 and 2019, there have been frequent interregional transfers of carbon emissions from transportation in the Pearl River Delta region, demonstrating a trend of shifting from economically developed areas to less developed areas.

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Research Progress on Energy Management Strategies and Capacity Configuration for Fuel Cell Ships

ZHANG Qinjin, SONG Zhe, ZENG Yuji, LIU Siyuan, LIU Yancheng, XIONG Feifan

2026, 45(2): 104-113. DOI: 10.3969/j.issn.1674-0696.2026.02.13

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To achieve the goal of reducing greenhouse gas emissions in the shipping industry, new energy power technologies with low-pollution and low-emission have brought new opportunities for the development of the shipping sector. Among them, fuel cell technology, with its unique advantages, has become a key direction in the research of new energy ships. In the design and development of fuel cell ships, energy management strategies and capacity configuration are two critical factors that are closely coupled and jointly affect the system performance. The relevant research on energy management strategies and capacity configuration optimization for fuel cell ships was summarized, highlighting the interrelationship between the two and their impact on ship design, which provided certain references for the subsequent design and development of fuel cell ships.

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Coupled Vibration Characteristics of Switched Reluctance Hub Motor under Complex Road Surface Excitation

ZHANG Haijun1，WANG Bolong1，ZHOU Zhe1,2，LI Jiaxin1，WU Xiaobo1

2026, 45(2): 114-121. DOI: 10.3969/j.issn.1674-0696.2026.02.14

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The hub motor driven electric vehicle is affected by the double excitation of the unbalanced radial force inside the motor and the external road surface roughness during the driving process, resulting in the coupled characteristics of the hub motor vibration. Aiming at the coupled vibration problem of switched reluctance hub motor under complex road surface excitation, the unbalanced radial force under the mixed eccentricity of the motor was taken as the excitation source alone. Combined with the complex road excitation consisting of random road surface and deterministic impact road surface, the 1/4 vibration system of the vehicle was established to analyze the dynamic responses such as stator acceleration, sprung mass acceleration and tire dynamic deformation. The results show that under the influence of internal and external coupled excitation, the stator acceleration, vehicle body acceleration and tire dynamic deformation will increase exponentially, and resonance is easy to occur near 1.5, 6.5 and 20.0 Hz.

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Molecular-Like Topology Design for Planetary-Row Hybrid Powertrain System

DENG Tao1,2,3, DENG Jiangchuan4 , RUI Guoqiang4, JIANG Lan4

2026, 45(2): 122-130. DOI: 10.3969/j.issn.1674-0696.2026.02.15

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The planetary row hybrid powertrain is widely utilized because of its highly efficient planetary row. For the planetary row hybrid powertrain system, a molecule-like topology design method for hybrid powertrain based on pattern screening is proposed, which not only effectively reduces the complexity during design, but also eliminates the powertrain configuration with duplicated functions. Furthermore, to prevent power cycling issues that reduce transmission efficiency in the configurations generated by this topology design method, a universal screening principle is introduced and incorporated into the screening process. Under this principle, the fuel economy of the optimized configurations improves by 5.56%. Through this topology design method, 173 hybrid systems with perfect performance and simple structures are finally obtained.

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