Pavement Stress Research Articles

Interlaminar Shear Characteristics of Typical Polyurethane Mixture Pavement.

Polyurethane (PU) can be used as a road material binder, and its mechanical properties, durability, temperature stability, and other road performance metrics are good. However, the interlayer bonding between PU mixtures and asphalt mixtures is poor. The influence of the pavement structure, interlayer treatment scheme, load, and environmental factors on the interlayer shear characteristics of PU mixture composite pavement is analysed. Further, dynamic modulus, Hamburg rutting, accelerated loading, and inclined shear tests were conducted, and the typical PU mixture pavement shear stress was calculated. The interlaminar shear stress of double layer PU mixture pavement, polyurethane–asphalt composite pavement, and typical asphalt pavement were calculated. The results showed that the PU mixture has a low rutting deformation rate, stable mechanical properties, and strong resistance to the coupled action of temperature, water, and loading. The double-layer PU mixture structure has good water-temperature stability and fatigue resistance; however, freeze–thaw and accelerated loading cause great damage to the double-layer PU mixture structure. The residual shear strength ratio after freeze–thaw cycles and accelerated loading is only 50.3% and 35.6%, respectively, while the influence on the double-layer asphalt mixture structure is less. The theoretical calculation results of different pavement structures show that when the temperature increases from 10 °C to 50 °C, the interlaminar shear stress of polyurethane–asphalt composite pavement increases by about 20%. Additionally, the shear stress of pavement PU mixture pavement and typical asphalt pavement is mainly affected by load, and the temperature changes have an obvious effect on the interlayer shear stress of polyurethane–asphalt composite pavement. The calculated maximum shear stress of the three pavement structures with different working conditions is less than the interlaminar shear strength measured by the inclined shear test, indicating that the interlaminar treatment scheme of composite specimens can meet the shear resistance requirements of the three typical pavement structure types.

A Study on the Design Depth of Permeable Road Pavement through Dynamic Load Experiment.

This study investigated vertical strain and stress through a dynamic load experiment at the testing area of Ke-Da Road, Pingtung, Taiwan. A thirty-five-ton truck was moved at constant speeds of 40, 60, and 80 km/h to simulate heavy load conditions to study the mechanical variations. From the results, it was found that the strain and stress curves of the permeable road pavement showed asymmetry due to the viscoelastic property of the open-grade friction course. The results showed that vertical strains and vertical stresses of permeable road pavement were greatly affected by the axle configuration and the change in traffic speed. Furthermore, to propose the design thickness of a permeable road pavement, the pavement strain and stress were modelled with respect to depth using regression based on these collected data. According to the stress regression models and considering the construction uncertainty, the recommend design depth of a permeable pavement is 30 cm. The findings of this study would be helpful in determining the permeable road pavement depth when subjected to heavy traffic load, and the material combination of open-graded friction concrete, porous asphalt concrete, and permeable cement concrete was proposed in this study during the design period.

Evaluation of the Effect of Average Annual Temperatures in Slovakia between 1971 and 2020 on Stresses in Rigid Pavements

The scientific community in Central Europe often discusses the extent to which temperature changes over the last two decades have contributed to changing the stresses induced in structures. In the field of road and environmental engineering, this question is especially pertinent for pavements. The pavement structure must first be defined methodologically by identifying and defining the types of parameters that change with time. Additionally, it is important to identify the areas of Central Europe that are most affected by climate change. The most important parameters must be described statistically for these areas. Slovakia is one of the countries that may be able to contribute to the solution of this issue due to its location in the middle of Europe. This paper provides a statistical analysis for the period from 1971 to 2020 in Slovakia. A concrete pavement, which is the most commonly used type of pavement, must be used as an example to numerical assess the situation. The conclusions and discussion in this scientific field are directed towards the evaluation of the measurement results in the context of the designed pavement composition and the calculations using the different methods specified in the standards.

Discrete element modelling of mechanical response of crumb rubber-modified asphalt pavements under traffic loads

ABSTRACT This study aims to predict the mechanical response of crumb rubber-modified (CRM) asphalt pavements under traffic loads using three-dimensional (3D) discrete element method (DEM). First, irregular-shaped aggregates were generated in Python language, and discrete element models of six different asphalt layers, which considered the temperature gradient and fatigue damage, were established using 3D DEM. Then, model parameters were obtained through the uniaxial creep test for asphalt mastics at different temperatures. The fatigue damage was implemented by introducing a damage factor into the Burgers model. Finally, three mechanical response parameters (namely, permanent deformation, shear stress and transverse strain) of the six asphalt layers under traffic loads were analysed and compared. Results show that the mechanical response of CRM asphalt layers under traffic loads is significantly influenced by number of repeated loads, temperature, and asphalt layer materials. The shear stress and transverse strain at the wheel centre vary along the depth of asphalt layers, and the middle layer is the principal area of shear stresses in asphalt pavements.

Interlayer residual stress analysis of steel bridge deck pavement during gussasphalt pavement paving

The interlayer shear stress in the steel bridge deck pavement (SBDP) and interlayer shear performance of waterproof bonding material change significantly during the gussasphalt mixture (GAM) paving, and interlayer residual stress may remain in the SBDP after the paving, which can affect the long-term performance of SBDP. The interfacial thermal resistance (ITR) parameter was proposed to represent the thermal resistance performance of waterproof bonding material firstly. A laboratory test and numerical simulation were carried out simultaneously through simulating the temperature variations of OSBD and GAM pavement during the paving, and the ITR values for three common waterproof bonding materials were determined by the least square method. The direct shear test was used to measure the shear performance variations of waterproof bonding layer during the GAM paving. The cohesive zone model (CZM) in the finite element (FE) method was used to characterize the interlayer shear performance variations of waterproof bonding layer during the paving, and the interlayer residual stress in the SBDP was calculated by the numerical simulation. The results showed that the ITR of the methyl methacrylate (MMA) bonding material is about two times that of HYPER-PRIMER (HYP) epoxy resin, and the ITR of 2910-type epoxy asphalt bonding material approximates zero. The waterproof bonding material with higher ITR values can reduce the highest temperature of steel bridge deck and interlayer residual stress during the paving to some extent, and the maximum interlayer residual stress after the gussasphalt pavement paving reaches 7.3 kPa.

FEM based parametric analysis for investigating effect of wheel base characteristics and axle configurations on flexural stresses in rigid pavements

The main advantages of rigid pavements are their durability and ability to hold their shapes when subject to heavy traffic and extreme weather conditions. Different vehicles have different wheel base characteristics and axle load configurations, due to which the above conditions structurally affect the performance of the rigid pavements in different ways. One of the main causes of critical defects in the rigid pavement is the development of flexural stress exceeding the critical level under different conditions. In rigid pavements the critical stresses are generated with the combination of wheel load stresses and curling stresses. In this paper, the investigation of the variation of flexural stress developed in jointed plain concrete pavements under different axle load configuration and wheelbase characteristics was done using FEM (Finite Element Method). In this paper, the modelling of the rigid pavement was carried out using KENPAVE software. In modelling, effect of both axle load and temperature difference is considered. For loading effect, axle configuration of SASW (Single Axle Single Wheel), SADW (Single Axle Dual Wheel), Tandem and Tridem axle was considered in modelling. To include the combined effect of base and subgrade an equivalent modulus of subgrade reaction was considered as per the IRC-58 code provisions. Parameters related to rigid pavement were taken according to the provisions of IRC code for modelling of base case. Parameters of pavement like thickness of pavement slab, equivalent modulus of subgrade reaction, temperature difference, modulus of elasticity and location of wheel load were changed from the base case and maximum tensile stress was calculated for each axle configurations. Based on the analysis of results for different thickness of pavement slab, equivalent modulus of subgrade reaction, temperature difference, modulus of elasticity and location of wheel load, the variation of magnitude and location of maximum tensile stress was reported for given properties of subgrade, base and axle configuration.

Study on the Influence and Law of Waterproof System Design Factors on the Typical Stress of Bridge Deck Pavement

To improve the structural design rationality of cement concrete bridge deck pavement systems and reduce diseases such as interlayer displacement and rutting in the early stage of bridge deck use, this paper studies the influence and law of the coupling effect of various factors of the waterproof system on the typical stress of bridge deck pavement and determines the best structure combination for the bridge deck pavement structure. A finite element model was established by using commercial software to simulate the mechanical response of different types of waterproof bonding layer, waterproof leveling layer, and impervious structure layer under different parameters. The simulation results show that when the thickness of the pavement layer was 8 cm, the maximum shear stress of the pavement layer occurred in the middle of the wearing course and the junction between layers. When the pavement layers were continuous, the maximum strain of the waterproof bonding layer with the “rubber asphalt + protective plate” structure in the transverse and longitudinal directions was the largest. When the waterproof leveling layer was cement concrete, the structure bore a large amount of stress and easily produced cracks, resulting in water damage. High-density water-based asphalt concrete with a low permeability coefficient can reduce the interlayer shear stress and effectively ensure the interlayer bonding effect. On this basis, the following bridge deck pavement structure was proposed: waterproof system + multifunctional waterproof layer + load-bearing structure layer + surface functional layer.

Improved Analytical Model and Algorithm for Computing Expansive Soil–Induced Stresses in Pavements

Abstract Estimating pavement internal forces due to the swelling or shrinking of expansive soils is of vital importance for planning, design, and construction. Such efforts can minimize some possib...

Evaluation of different modulus input on the mechanical responses of asphalt pavement based on field measurements

As a key input parameter of asphalt pavement design, the modulus parameters directly affect the results of pavement stress analysis. During the mechanical evaluation analysis, researchers usually use material modulus instead of structural modulus as input parameter, so the possible deviations between the field measured mechanical responses and the calculated responses are ignored in this case. Therefore, the field mechanical response and the calculations mechanical response of finite element method (FEM) with different moduli input were evaluated in this research. The field strains of each pavement layer under dynamic and static load conditions were determined by embedding the fiber Bragg grating (FBG) sensors, and the field deflection test was carried out by Beckman beam. A total of 11 types of material moduli were obtained through various modulus tests, and which were implemented in the FEM model for the strain and deflection calculation of pavement structure, and then the calculated mechanical responses were compared with the field measured mechanical responses. The results indicated that a specific modulus should be selected to ensure the calculated value effectively reflect the measured mechanical response. For the FEM calculation of dynamic strain, it is recommended to use static flexural modulus for asphalt layer and use dynamic flexural modulus for CSG layer as modulus input with average errors of 16.9% and 7.5% respectively. For the FEM calculation of static strain, it is recommended to use dynamic compressive resilience modulus for asphalt layer and use static flexural modulus for CSG layer as modulus input with average errors of 18.7% and 11.5% respectively. Besides, it is recommended to select dynamic flexural modulus or compressive modulus in static four-point bending test as the modulus input for pavement deflection analysis with the error of about 4.8%.

Calibration of pavement ME rutting model for geogrid stabilized roadways

Many transportation agencies started implementing Mechanistic-Empirical (ME) approach for designing and analyzing new and rehabilitated pavements. Although the widely popular empirical design approach based on 1993 AASHTO Design Guide is still in practice, the need for performance-based design and accurate prediction of pavement distresses throughout the service life led to the adoption of the ME approach. The two major steps associated with the ME approach are the computation of pavement stress–strain responses using mechanistic analysis and estimation of pavement distresses using empirical analysis. Layered Elastic Analysis (LEA) or Finite Element Analysis (FEA) is normally utilized for mechanistic analysis whereas regression analysis is typically used for empirical analysis. Although the empirical models (i.e., transfer functions) were calibrated using the Long Term Pavement Performance (LTPP) dataset, these models do not consider the benefits of geogrid stabilization. Research and field studies had shown improvement in pavement performance when the pavement is stabilized with geogrids. This paper aims at incorporating the effect of geogrid in one of the distress models – more specifically, the rutting model – of AASHTOWare Pavement ME. Model calibration factors were developed based on the recent full-scale accelerated pavement test conducted at the research facility of the US Army Corps of Engineers. Two types of punched and drawn triangular aperture geogrids were utilized in the full-scale test. Pavement surface deformations measured during the trafficking period were used for calibrating the rutting model. The calibrated rutting model was validated with the LTPP and Louisiana Transportation Research Center (LTRC) dataset.

Technical Proposal for Monitoring Thermal and Mechanical Stresses of a Runway Pavement

Airport pavements should ensure regular and safe movements during their service life; the management body has to monitor the functional and structural characteristics, and schedule maintenance work, balancing the often conflicting goals of safety, economic and technical issues. This paper presents a remote monitoring system to evaluate the structural performance of a runway composed of concrete thresholds and a flexible central runway. Thermometers, strain gauges, and pressure cells will be embedded at different depths to continuously monitor the pavement’s response to traffic and environmental loads. An innovative system allows data acquisition and processing with specific calculation models, in order to inform the infrastructure manager, in real time, about the actual conditions of the pavement. In this way, the authors aim to develop a system that provides useful information for the correct implementation of an airport pavement management system (APMS) based on real-life data. Indeed, it permits comprehensive monitoring functions to be performed, based on the embedded sensing network.

Comparative analysis of stress distributions and displacements in rigid and flexible pavements via finite element method

In many countries of the world, rigid and flexible pavements are widely used. Some of the external factors such as stresses and displacements play major role in the design of pavement layers such as coating, base and sub-base. Although empirical formulas and methods were used in the calculation and design of the pavement layers, complexity of today's transportation engineering demands effectiveness of the empirical formulas were diminished. Nowadays complex problems can be easily simulated and solved thanks to the higher analysis capabilities of the computer-aided softwares. In this study, the stress distributions and displacements were examined under traffic loads in rigid and flexible pavements with different coating layer thicknesses (30 mm, 50mm, 70mm, 100 mm, and 150 mm) by using finite element method. As a result, the vertical displacement in the flexible pavements were obtained as 5% higher than the vertical displacement in the rigid pavements. Based on the stress distribution results, the stress values of flexible pavements were 60% lower than the stress values of the rigid pavements. Moreover, It was determined that the stresses in the rigid pavements remain in the coating layer, while the stresses in the flexible pavements reach the base and sub-base. In addition, regression models have been developed to predict stress and displacements by using layer thicknesses. High correlation and determination coefficient values (> 0.90) were achieved based on the regression analysis both in flexible and rigid pavements.

Stress behavior of concrete pavement

Warping stresses and flexural stresses due to variation of thermal gradient and wheel load, respectively, cause cracking of rigid pavement. The distress in the pavement structure can be happened because of warping stresses induced by thermal gradient which causes curling effect due to temperature variation. The wheel load resulted flexural stresses which varies with the position and depends upon contact condition and repetition of load at a specific time interval. In the present study, a comparison of stresses of single layered rigid concrete pavement due to thermal load and wheel load have been done with varying slab thicknesses and modulus of subgrade reactions. The pavement has been modeled and analysed using SAP2000 finite element software. During modeling, the single layered rigid concrete pavements comprising of PQC has been considered without any joints at edges. The PQC slab has been considered with dense liquid foundation i.e. elastic. The self weight of pavement has been excluded in the analysis. It has been found that the interior thermal warping stresses are more sensitive with respect to slab thicknesses than modulus of subgrade reactions. It can also be stated that there is significant impact on stress behavior of the pavement due to combined effect of thermal gradient along with wheel load, especially for positive and negative thermal gradient considerations.

Simulation Analysis on Temperature Field and Temperature Stress of Flexible Pavement in Cold Areas

In order to ensure the service life of pavement in cold areas, this paper simulates the temperature field and stress field of pavement at high temperature of 60˚C and low temperature of -30˚C based on ANSYS software, and analyzes the changing trend of temperature of each layer with time and the temperature stress caused by it using the time-incremental finite element method. The results show that when the temperature is higher than 0˚C, the temperature between layers of the structure and the surface temperature shows an increasing trend. On the contrary, when the temperature is lower than 0˚C, it shows a decreasing trend. The more drastic the temperature change is, the greater the temperature stress of the pavement will be, which is easy to cause road structure diseases. When the temperature difference of pavement reaches 90˚C, the change of temperature stress between layers of road structure has a significant effect on the daily evolution of pavement.

Parameter Optimization of Graded Macadam Transitional Layer for Inverted Asphalt Pavement Based on the Mechanical Response and Strength Standard

To improve the durability of asphalt pavement with heavy traffic conditions in cold regions, the parameter optimization of graded macadam transitional layer (GMTL) for the inverted asphalt pavement based on the mechanical response and the strength standard was studied. The stress distribution laws of GMTL were studied with different loads by means of BISAR3.0. The influences of the thickness and the modulus of GMTL on the pavement stress were analyzed. The optimal thickness and the modulus range of the GMTL were determined. Combined with a self‐developing real‐time data acquisition and a processing system for aggregate attitude (RDAPS), the strength control standard of the GMTL was established. Finally, the performance of the optimized inverted asphalt pavement structure was verified through the MEPDG design method. The results show that the tensile stress at the bottom of the surface layer reduced by about 58%, and the shear stress in GMTL increased by about 17% when the modulus of GMTL increases from 300 MPa to 800 MPa. However, the change in modulus has no significant influence on the maximum shear stress in the asphalt surface layer and the tensile stress in the base layer bottom. When the thickness of GMTL increases from 12 cm to 20 cm, the tensile stress in the bottom of the base layer reduced by about 31%. Based on the mechanical results from simulation calculation and the technical indicator required in the field, the recommended optimal parameters of GMTL are the modulus of 700 MPa and the thickness of 18 cm. In addition, the spatial attitude angle ΦN of wireless intelligent attitude aggregate (WIAA), the compressive strength Rc standard, and the California Bearing Ratio (CBR) standard were analyzed, and the strength control standard of inverted asphalt pavement with GMTL was proposed, namely, CBR ≥ 354%, Rc ≥ 1.06 MPa, and ΦN ≤ 3°. A significant improvement in the resistance to crack can be seen in the inverted asphalt pavement when the optimized structure was applied. Taking the 20‐year service life as an example, the top‐down cracks reduced by 29.3% and the bottom‐up cracks reduced by 32.6% in comparison to the original structure. The recommended structural parameters of GMTL could be used to guide the construction and design of inverted asphalt pavement in cold regions.

Study on simulation mechanics and fatigue performance of steel bridge deck rigid flexible composite pavement

Aiming at the fatigue cracking of steel bridge deck pavement and the shortage of river sand resources, a sea sand RPC pavement scheme was proposed. Taking Quanhe steel box girder bridge as the research background, the simulation model was established by using ANSYS finite element software, and the mechanical simulation analysis of the steel bridge deck sea sand RPC-asphalt pavement composite structure was carried out to determine the most unfavorable load position. A three-point fatigue test was carried out to study the fatigue performance of the structure specimen, and a comparative analysis was made with the river sand RPCasphalt surface composite pavement structure. The results show that the maximum tensile stress and strain of RPC-asphalt pavement appear in the upper middle span of U-shaped stiffener of steel box girder, which are 0.5241MPa and 98.2με, respectively, and the surface of the pavement in this area is prone to crack. The RPC-asphalt surface composite pavement structure has not been damaged after 2 million times of fatigue tests, and has not been damaged after 1 million times of fatigue loading after secondary loading, which indicates that it has better fatigue performance.

Mechanical characteristics research of new asphalt pavement structure based on geogrid

In order to study the mechanical characteristics of new asphalt pavement structural materials, UTM testing machine and Overlay Test (OT) testing machine, four-point fatigue test, tensile test and bending strength test have been carried out on different types of grid asphalt mixtures. The result shows: the addition of different types of grids can effectively improve the mechanical properties of the asphalt concrete pavement structure; geogrid addition can improve the stress on the road surface, improve the strength of pavement materials, it can effectively alleviate early generation of fatigue cracks on the road surface; it can also effectively avoid the problem of rutting damage on the whole road surface after partial damage to the road surface; can effectively promote pavement stress dispersion, improve pavement structure stability, make the pavement structure more stable, improve its service life.

Adaptability of asphalt pavement structures to deformation of embankment underlain by black cotton soil

Three pavement structures, including fatigue-resistant layer sandwich structure (FRLSS), sandwich asphalt pavement structure (SAPS) and semi-rigid base pavement structure (SRBPS), were designed to investigate their adaptability to the differential deformation of highway embankment on black cotton soil (BCS), which shrink/swell behavior was modeled by the coupled consolidation theory for unsaturated soils. The maximum additional tensile stress in pavement was obtained, and the present serviceability index (PSI) and the international roughness index (IRI) were calculated by the vertical movement, pavement properties and traffic data. The adaptability of those pavement structures to the differential deformation of highway embankment was evaluated by grey relational analytical method using the PSI, IRI and additional tensile stress as the indexes. The results reveal that FRLSS presents the better effect in controlling cracks on the key-layer bottom, while SRBPS presents the better effect in controlling cracks on the pavement surface. The effect in controlling roughness decreases gradually from FRLSS, SAPS to SRBPS in order. The adaptability of FRLSS to the soil movement of highway embankment on BCS is superior to SAPS, which excels SRBPS. Overall, FRLSS should be given priority in designing asphalt pavement underlain by BCS foundation from the perspective of controlling roughness and cracks.

Numerical analysis on distribution and response of acceleration field of pavement under moving load

In the previous studies on the dynamic responses of pavement, most researchers paid attention to the stress and strain responses of pavement. With the passings of vehicles, road structures will inevitably produce vibration accelerations. Since acceleration is closely related to many physical quantities according to the definitions in physics, the acceleration of pavement can reflect pavement conditions from the side, and the relevant studies on the acceleration field of pavement under moving load are worth conducting. In this study, with the help of ABAQUS, the numerical analysis on the distribution and response of the acceleration field of pavement under moving load was carried out, and the influencing degrees of vehicle load, vehicle speed and the elastic modulus of upper layer on the acceleration response of intact pavement were also compared based on the designed orthogonal test. It was found that the three-directional accelerations of pavement present symmetrical distributions around the loaded area, and the vertical acceleration is the largest but decays rapidly with the form of quartic polynomials as far away from the loaded area. Meanwhile, the mechanical state of pavement can be evaluated by analyzing pavement accelerations. Besides, the acceleration response of the intact pavement in this study is the most sensitive to the influencing factor of vehicle speed, followed by vehicle load, and the brought effect of the elastic modulus of upper layer is the lowest in general.

The role of temperature differential and subgrade quality on stress, curling, and deflection behavior of rigid pavement

Abstract To determine performance of rigid pavement, pavement engineers should not only conduct stress, curling, and deflection analysis, but also understand weather conditions and subgrade quality effects on rigid pavement performance well. This study aims to analyze and visualize the mechanical behaviors of rigid pavement in terms of stress, curling, and deflection using the KENPAVE Program under different curling temperature and subgrade quality. Besides, this study also evaluated temperature differential and k-value effects on the stress, curling, and deflection behavior of concrete pavement. The findings revealed that there is a linear correlation between stress and both k-value and curling temperature, with the latter having more significant impact in controlling stress than the former. However, even though curling is not affected by subgrade quality, it significantly depends on the temperature differential since a higher curling temperature produces higher curling behavior. Lastly, a higher temperature differential produces greater deflection, but a higher k-value produces smaller deflection. Nevertheless, deflection behavior has a more significant curve and the position of the highest deflection shifted towards the center of the slab as the curling temperature and subgrade quality increase.