Search Results (77)

With the rapid increase in traffic volume and the number of heavy-duty vehicles, the load on asphalt pavements has increased significantly. Especially on sections with long longitudinal slopes, the internal stress conditions of asphalt pavement have become even more complex. This study aims to investigate the thermal–mechanical coupling behavior of asphalt pavement structures on long longitudinal slopes under the combined influence of temperature fields and moving loads. A pavement temperature field model was developed based on the climatic conditions of Nanning (AAT: 21.8 °C; Tmax: 37 °C; Tmin: 3 °C; AAP: 1453.4 mm). In addition, a three-dimensional finite element model of asphalt pavement structures on long longitudinal slopes was established using finite element software. Variations in pavement mechanical responses were compared under different vehicle axle loads (100–200 kN), slope gradients (0–5%), braking coefficients (0–0.7), and asphalt mixture layer thicknesses (2–8 cm). The results indicate that the pavement structure exhibits a strong capacity for pressure attenuation, with the middle and lower surface layers showing more pronounced stress reduction—up to 40%—significantly greater than the 6.5% observed in the upper surface layer. As the axle load increases from 100 kN to 200 kN, the internal mechanical responses of the pavement show a linear relationship with load magnitude, with an average increase of approximately 29%. In addition, the internal shearing stress of the pavement is more sensitive to changes in slope and braking coefficient; when the slope increases from 0% to 5% and the braking coefficient increases from 0 to 0.7, the shear stress at the bottom of the upper surface layer increases by 12% and 268%, respectively. This study provides guidance for the design of asphalt pavements on long longitudinal slopes. In future designs, special attention should be given to enhancing the shear strength of the surface layer and improving the interlayer bonding performance. In particular, under conditions of steep slopes and frequent heavy vehicle traffic, the thickness and modulus of the upper surface asphalt mixture may be appropriately increased. Full article

The effects of heavy traffic and complex natural environmental conditions have made the problem of the inadequate life expectancy of asphalt pavements increasingly pronounced. In this study, finite-element software was used to establish the three-dimensional analytical model of temperature-load coupling under different axial loads and calculate the distribution law of temperature-load coupling stress under the most unfavorable loading conditions. By comparing temperature and coupled stresses at different depths, the extent to which combined stress changes due to environmental factors affect different depths was determined. Finally, the fatigue life patterns of asphalt pavements under different seasons and axle loads were analyzed. The results showed that the temperature-load coupling stress varied periodically under different axial loads. Among them, the temperature stress had less influence on the coupling stress in spring and fall and more influence in winter. As the depth increases, the coupling stresses and their range of influence gradually decrease. Also, the farther away from the wheel load position, the smaller the traveling load disturbance and the closer the coupling stresses were to the temperature stresses. Under the most unfavorable loading conditions, the change rule of the degree of influence of environmental effects along the depth direction showed that the winter gradually decreased, the spring and fall seasons for the first time decreased and then increased, and the minimum influence on the road surface was at 9 cm. Overall, the degree of influence of environmental action at different axial loads was 70.53%, 41.90%, 27.13%, and 23.77% along the depth direction. Full article

The structural integrity of cement concrete pavements, paramount for ensuring traffic safety and operational efficiency, faces mounting challenges from the escalating burden of heavy-duty vehicular traffic. Precise characterisation of pavement dynamic responses under such conditions proves indispensable for implementing effective structural health monitoring and early warning system deployment. This investigation examines the triaxial dynamic response characteristics of cement concrete pavement subjected to low-speed, heavy-duty vehicular excitations, employing data acquired through in situ field measurements. A monitoring system incorporating embedded triaxial MEMS accelerometers was developed to capture vibration signals directly within the pavement structure. Raw data underwent preprocessing utilising a smoothing wavelet transform technique to attenuate noise, followed by empirical mode decomposition (EMD) and short-time energy (STE) analysis to scrutinise the time–frequency and energetic properties of triaxial vibration signals. The findings demonstrate that heavy, slow-moving vehicles generate substantial triaxial vibrations, with the vertical (Z-axis) response exhibiting the greatest amplitude and encompassing higher dominant frequency components compared to the horizontal (X and Y) axes. EMD successfully decomposed the complex signals into discrete intrinsic mode functions (IMFs), identifying high-frequency components (IMF1–IMF3) associated with transient vehicular impacts, mid-frequency components (IMF4–IMF6) presumably linked to structural and vehicle dynamics, and low-frequency components (IMF7–IMF9) representing system trends or ambient noise. The STE analysis of the selected IMFs elucidated the transient nature of axle loading, revealing pronounced, localised energy peaks. These findings furnish a comprehensive understanding of the dynamic behaviour of cement concrete pavements under heavy vehicle loads and establish a robust methodological framework for pavement performance assessment and refined axle load identification. Full article

With the increase in heavy-load traffic and the growing frequency of extreme weather events, traditional rock aggregates, due to poor morphological stability, are unable to meet the performance requirements of high-grade asphalt pavements in complex environments. Most existing research on metal reinforcement focuses on fiber forms. This study innovatively introduces L-shaped multi-faceted metal aggregates (LFMAs). Through surface energy analysis and tests such as the Marshall test, rutting test, water immersion Marshall test, and freeze–thaw splitting test, the effects of the dosage and particle size of LFMAs on the performance of asphalt mixtures are explored. The results show that LFMAs can form an effective bond with SBS modified asphalt, improving the high-temperature stability and low-temperature crack resistance of asphalt mixtures. Under both water immersion and freeze–thaw conditions, the resistance of asphalt mixtures to water damage decreases with the increase in the dosage of metal aggregates. This research expands the application of three-dimensional metal aggregates, breaks through the limitations of fiber-based materials, and provides a new direction for the development of high-performance asphalt mixtures. Full article

During the operation of outdoor heavy-duty Automated Guided Vehicle (AGV), the stability and safety of AGV are easily reduced due to load transfer. In order to solve this problem, a trajectory tracking control strategy considering load transfer is proposed to realize the trajectory tracking of AGV and the adaptive distribution of driving torque. The three-degree-of-freedom (3-DOF) kinematics model and pose error model of heavy-duty AGV vehicles are established. The lateral load transfer and longitudinal load transfer rules are analyzed. The vehicle trajectory tracking control strategy is composed of an improved model predictive controller (IMPC) and drive motor torque adaptive distribution controller considering load transfer. By optimizing the lateral acceleration of the vehicle body, the IMPC controller improves the problem of large driving force difference between the left and right sides of the wheel caused by the lateral transfer of the load and the problem of large wheel adhesion rate caused by the longitudinal transfer of the load is improved by the speed controller and the torque proportional distribution controller. The joint simulation platform of MATLAB/Simulink and CarSim is built to simulate and analyze the trajectory tracking of heavy-duty AGV under different pavement adhesion coefficients. The simulation results have shown that compared with the control strategy without considering load transfer, on the two types of pavements with different adhesion coefficients, the maximum lateral acceleration is reduced by 19.7%, and the maximum tire adhesion rate is reduced by 11.5%. Full article

Asphalt pavements are subjected to both repeated vehicle loads and erosive deterioration from complicated environments in service. Salt erosion exerts a serious negative impact on the service performance of asphalt pavements in salt-rich areas such as seasonal frozen areas with snow melting and deicing, coastal areas, and saline soils areas. In recent years, the performance evolution of asphalt materials under salt erosion environments has been widely investigated. However, there is a lack of a systematic summary of salt erosion damage for asphalt materials from a multi-scale perspective. The objective in this paper is to review the performance evolution and the damage mechanism of asphalt mixtures and binders under salt erosion environments from a multi-scale perspective. The salt erosion damage and damage mechanism of asphalt mixtures is discussed. The influence of salt categories and erosion modes on the asphalt binder is classified. The salt erosion resistance of different asphalt binders is determined. In addition, the application of microscopic test methods to investigate the salt damage mechanism of asphalt binders is generalized. This review finds that the pavement performance of asphalt mixtures decreased significantly after salt erosion. A good explanation for the salt erosion mechanism of asphalt mixtures can be provided from the perspective of pores, interface adhesion, and asphalt mortar. Salt categories and erosion modes exerted great influences on the rheological performance of asphalt binders. The performance of different asphalt binders showed a remarkable diversity under salt erosion environments. In addition, the evolution of the chemical composition and microscopic morphology of asphalt binders under salt erosion environments can be well characterized by Fourier Infrared Spectroscopy (FTIR), Gel Permeation Chromatography (GPC), and microscopic tests. Finally, the major focus of future research and the challenges that may be encountered are discussed. From this literature review, pore expansion mechanisms differ fundamentally between conventional and salt storage asphalt mixtures. Sulfate ions exhibit stronger erosive effects than chlorides due to their chemical reactivity with asphalt components. Molecular-scale analyses confirm that salt solutions accelerate asphalt aging through light-component depletion and heavy-component accumulation. These collective findings from prior studies establish critical theoretical foundations for designing durable pavements in saline environments. Full article

Conventional concrete does not often meet engineering needs in high-impact scenarios, such as airport runways and bridges, due to its brittleness, low tensile strength and insufficient resistance to dynamic loading. Although existing rubberized concrete exhibits an enhanced toughness, granular rubber exhibits significantly poorer mechanical properties, limiting its wide application. For this reason, in this study, we propose incorporating rubber in the form of fiber and systematically investigate the effects of the rubber fiber type (NBR, silicone rubber, EPDM), admixture amount (5%, 10%, 15%) and length (6, 12, 18 mm) on the mechanical properties and impact resistance of concrete. Through cubic compression, split tensile and drop hammer impact tests, combined with SEM microanalysis and Weibull distribution modeling, the trends in properties and the mechanisms of action were revealed. The key findings included the following: (1) The equal-volume replacement of fine aggregates with fibrous rubber significantly reduced the static strength, with NBR exhibiting the lowest compressive strength loss (13.12%) compared to silicone rubber (30.86%) and EPDM (21.52%). The splitting tensile strength decreased by 10.11%, 23.67% and 13.56%, respectively. (2) The rubber dosage was negatively correlated with static strength, while an increased fiber length partially mitigated strength degradations. (3) Fibrous rubber markedly enhanced impact resistance: the final crack impact cycles of NBR, silicone rubber and EPDM were increased by 255%, 147.5% and 212.5%, respectively, compared to plain concrete. The optimal mix (15% dosage, 12mm NBR) improved the impact life by 330%. (4) Weibull distribution analysis confirmed that the impact resistance data conformed to a two-parameter model (R² ≥ 0.808), with a high consistency between the predicted and experimental results. The results of this research can be applied to transportation infrastructures (e.g., heavy-duty pavements, bridges) that require a high impact resistance, with environmental benefits. However, the study did not analyze the long-term durability (e.g., effects of freeze–thaw and chemical corrosion) or perform an economic analysis of rubber fiber processing costs; this needs to be further explored in the future to promote practical engineering applications. Full article

Due to prolonged heavy traffic, the Wuhan Changfeng Bridge has experienced extensive cracking in its main girder structure. Of the bridge’s 60 crossbeams, 51 (85%) have developed cracks, while the deck pavement over the steel beams has accumulated a total of 648.8 m of transverse cracks. Additionally, two T-beams exhibit structural vertical cracks of 0.3 mm at the mid-span, exceeding the maximum allowable width of 0.2 mm. This recurrent pavement damage not only compromises driving safety and comfort but also increases maintenance costs. To address these issues, this paper proposes a systematic upgrade plan for the bridge deck system. The plan involves welding additional high transverse beams onto the existing steel transverse beams, removing the original deck slab and replacing it entirely with an orthotropic steel deck. Additionally, two new steel longitudinal beams will be installed. The original simply supported concrete longitudinal beams in the deck will be transformed into an integrally connected continuous steel structure deck system. Using Midas/Civil finite element software, 3D models of Changfeng Bridge, pre and post renovation, were created to analyze the overall dynamic characteristics under five loading scenarios. The ambient vibration test and vehicle field test were conducted to measure the bridge’s natural frequency and impact factor, verifying the dynamic performance and driving comfort of the bridge after the upgrade. The results indicate that the retrofitted bridge experienced a 19.9% increase in overall stiffness. The dynamic performance of the bridge structure was significantly enhanced, and the most notable improvement was observed in dynamic stress, which decreased by 19.4% to 76.9%. Additionally, the steel deck reduced the bridge’s dead load, and the driving comfort on the bridge deck improved. Full article

Asphalt pavement durability significantly impacts the service life of roads, and hence, understanding the performance of high-performance asphalt mixtures is crucial. This study investigates the performance of four high-performance asphalt mixtures: heavy-load AC-20, high-viscosity AC-20, heavy-load SMA-13, and heavy-load SMA-10. Linear Amplitude Sweep (LAS) tests revealed that heavy-load asphalt mixtures exhibit superior fatigue resistances, with the fatigue life of heavy-load SMA-13 exceeding 1.5 times that of high-viscosity AC-20 under similar stress levels. Bending Beam Rheometer (BBR) tests at −6 °C, −12 °C, and −18 °C demonstrated that both heavy-load and high-viscosity asphalts had comparable low-temperature crack resistance, with heavy-load SMA-13 showing a stiffness modulus of 627 MPa at −18 °C. Marshall tests indicated that heavy-load AC-20 had the highest stability (14.3 kN) among the tested mixtures, while heavy-load SMA-13 exhibited the highest density (2.603 g/cm³). Dynamic modulus tests spanning a frequency range of 10⁻⁴ Hz to 10⁵ Hz at various temperatures showed that heavy-load SMA-13 had a higher dynamic modulus than heavy-load SMA-10, particularly at lower frequencies (higher temperatures). Rutting tests at 60 °C indicated that heavy-load SMA-13 had the lowest rut depth (18.5 mm), outperforming other mixtures by up to 25%. The heavy-load SMA-13 asphalt mixture demonstrated the best overall performance, especially in terms of high-temperature stability, fatigue resistance, and rutting resistance. This study provides essential material performance parameters for the development of durable high-performance asphalt pavement structures. Full article

The behavior of airport precast concrete pavement (APCP) involving new design and construction concepts was experimentally analyzed under environmental and moving airplane loads, and the long-term performance of the APCP was evaluated using fatigue failure analysis. The strain characteristics and curling behavior of the APCP under environmental loads were comprehensively analyzed. The APCP slabs exhibited a pronounced curling phenomenon similar to conventional concrete pavement slabs. The dynamic response of the APCP subjected to impact loads was analyzed by performing heavy weight deflectometer tests. The test results confirmed that the vertical deformation of the APCP was small and within the typical range of vertical deformation of conventional concrete pavement. The dynamic strain response of the APCP under moving airplane loads was then analyzed and the strain variation during day and night times was compared. The strains during the day were found to be significantly larger than those at night under airplane loads because of the curling phenomenon of the APCP slabs. Finally, the long-term performance of the APCP was evaluated using fatigue failure analysis based on the obtained behavior. Even using the most conservative fatigue failure prediction model, the service life of the APCP was ascertained to be more than 30 years. Based on the overall results of this study, it is concluded that the APCP, which is designed to reduce slab thickness by placing reinforcing bars in the slabs via reinforced concrete structural design, exhibits typical behavior of concrete pavements and can be successfully applied to airport pavement rehabilitation. Full article

Over the past few decades, flexible pavements across the globe have seen a significant reduction in their service life due to climate changes. The flexible pavements with unsaturated subgrades undergo volumetric changes during the drying and wetting phases, affecting their long-term deformation behavior. These phases cause significant variations in matric suction and groundwater table depth. This study employs a coupled pore pressure-deformation analysis on flexible pavements to investigate the impact of groundwater table depth and suction variations in unsaturated subgrades. Finite-element simulations using the Abaqus and developed USDFLD code were validated against literature data. Sensitivity analysis was conducted by varying the suctions in subgrades during drying and subsequent wetting to evaluate the groundwater table depth. Furthermore, under heavy cyclic wheel loading, pavement-deformation analysis was conducted to investigate the influence of subgrade suction. The findings demonstrate that, after an initial drying phase at 5000 kPa suction, wetting over 180 days caused the groundwater level to rise from 5.45 m beneath the subgrade to the surface. This led to a 98% increase in surface-vertical deformations due to cyclic wheel loading after 180 days of wetting compared to the deformations during the drying phase at the same suction level. This assessment of groundwater-depth variations and long-term deformation behavior with the impact of suction improves the design and sustainability of flexible pavements. Full article

Previous studies indicate that traditional asphalt mixtures lack the ability to withstand the stresses caused by heavy traffic volumes under high temperatures. To enhance the rutting resistance of flexible pavement under high levels of temperature and loading, extensive laboratory experiments were carried out. A 60/70 grade bitumen was used as a neat sample for comparison. The study introduced three distinct polymers, polypropylene (PP), low-density polyethylene (LDPE), and acrylonitrile butadiene styrene (ABS), at varying concentrations by weight into the neat bitumen. Initially, conventional tests were performed to evaluate the conventional properties of both the neat and modified bitumen, while aggregate tests assessed the mechanical properties of the aggregates. Subsequently, a Marshall mix design was performed to determine the optimum bitumen content (OBC) in the asphalt mixture. Finally, wheel-tracking tests were performed under a specific load and temperature to investigate the rutting behavior of the modified asphalt mixtures. The results of this comprehensive study revealed that the modified asphalt mixtures displayed improved resistance to rutting compared to the neat asphalt mixture. Furthermore, it was also observed that the LDPE exhibited a superior performance against rutting, followed by the PP and ABS. At polymer contents of 3%, 5%, and 7%, the LDPE achieved reductions in rut depth of 13%, 24%, and 33%, respectively, outperforming both PP- and ABS-modified asphalt. These findings not only enhance our understanding of asphalt behavior under diverse conditions but also highlight the potential of plastic-modified asphalt as an effective solution for mitigating rutting problems in road pavements. By incorporating plastic modifiers into asphalt mixtures, this approach aligns with the principles of sustainable construction by reducing plastic waste while improving pavement durability and performance. Full article

With the rapid development of China’s transportation network, the demand for bridge construction is increasing, the traffic volume is increasing yearly, and the average vehicle speed and the frequency of overloaded vehicles crossing bridges are soaring. When a vehicle passes over a highway bridge, it can easily form a coupling vibration between the vehicle and bridge due to the excitation of the expansion joint, the unevenness of the bridge deck, and the existing coating-hole. The impact effect is significant, which seriously affects the operation safety of both the vehicle and bridge, seriously damaging the service life of the bridge. Due to the influence of construction technology, it is common for the vibration to meet transverse and longitudinal expansion joints of a prefabricated girder bridge, where an aging bridge deck frequently results in bulges and potholes in asphalt pavement. The bridge vibration amplification effect under the dynamic load of heavy, high-speed vehicles is significant, and research about the large impact coefficient of bridges with local pavement deterioration is urgently needed. This study used SIMULINK simulation software and involved conducting several bridge model tests. Dynamic simulation analyses and running vehicle tests on scaled and real bridge models were carried out to study the coupling vibration response of bridge decks in the presence of different pothole sizes. The results show that the impact effect of low-speed vehicles passing through a larger-sized pothole is relatively significant, and the impact coefficient can be amplified to 214% of the original value under good road surfaces in extreme cases. The vehicle–bridge coupling impact effect of potholes is similar to bulges. This relevant work could provide suggestions for the operational performance evaluation and maintenance of bridges with local pavement deterioration. Full article

In asphalt pavement structure design, traffic axle loads and pavement layer temperatures are crucial factors affecting fatigue damage calculations. To investigate the differences in fatigue damage calculations caused by different characterizations of traffic axle loads and temperature, fatigue damage calculations were conducted under equivalent standard axle loads (ESALs), axle load spectra (ALS), constant temperatures, and seasonal temperature variations using the field data from an expressway in Shandong Province, China under seven calculation plans. The results indicated: (1) the annual traffic composition is dominated by vehicle Type 9, with a proportion of about 43% in all the vehicle types, and its load level is also high, with a proportion about of 80% in the heavy load interval at all axle types; (2) The ESALs method underestimates the actual fatigue damage incurred in asphalt pavement by 6.04 times, with an accumulated damage of 2.34 × 10⁻⁹ (ESALs), 1.69 × 10⁻⁸ (ALS), respectively; (3) The fatigue damage results from a single month with consistent temperature showed similar trends, with an accumulated damage of 1.50 × 10⁻⁵, 9.07 × 10⁻⁵, respectively; (4) The cumulative fatigue damage calculated using the ALS method across the four seasons, respectively, is 6.51, 5.88, 6.42, and 4.60 times that of the fatigue damage calculated using the ESALs method. Although the ratio of fatigue damage between the two characterizations of traffic axle loads remains consistent, which is 6.04, the fatigue damage calculation that accounts for temperature variations can reveal seasonal trends in fatigue damage development. Based on the axle load spectra and considering temperature variations, fatigue damage calculation will be more closely related to the actual service state of asphalt pavement. These research findings provide insights for estimating asphalt pavement fatigue damage to some extent. Full article

Permeable road pavements, due to their open-graded design, suffer from low structural strength, restricting their use in areas with light traffic volume and low bearing capacity. To expand application of permeable road pavements, accurate simulation of stress parameters used in pavement design is essential. A 3D finite element (3D FE) model was developed using ABAQUS/CAE 2021 to simulate pavement stress responses. Utilizing a 53 cm thick permeable road pavement and a 315/80 R22.5 wheel as prototypes, the model was calibrated and validated, with its accuracy confirmed through t-test statistical analysis. Simulations of wheel speeds at 11, 15, and 22 m/s revealed significant impact on pavement depths of 3 cm and 8 cm, while minimal effects were observed at depths of 13 cm and 33 cm. Notably, stress values at a depth of 3 cm with 15 m/s speed in the open-graded asphalt concrete (OGFC) surface layer exceeded those at the speed of 11 m/s, while at a depth of 8 cm in the porous asphalt concrete (PAC) base layer, an opposite performance was observed. This may be attributed to the higher elastic modulus of the OGFC surface layer, which results in different response trends to velocity changes. Overall, lower speeds increase stress responses and prolong action times for both layers, negatively affecting pavement performance. Increasing the moduli of layers is recommended for new permeable road pavements for low-speed traffic. Furthermore, considering the effects of heavy loads and changes in wheel speed, the recommended design depth for permeable road pavement is 30 cm. These conclusions provide a reference for the design of permeable road pavements to address climate change and improve performance. Full article