Pavement Stress Research Articles

A mechanistic approach to evaluate the potential of the debonding distress in asphalt pavements

The debonding distress in asphalt pavement structures is a critical problem that affects the performance of asphalt concrete pavements. It occurs at the layer interface due to the poor bond quality between adjacent asphalt concrete layers and/or when stresses at the layer interface exceed the strengths of the material at the interface. The debonding of the adjacent layers, especially the top surface layer of an asphalt pavement, is a contributing factor to the premature cracking of pavements. Hence, the debonding distress can lead to a reduction in the life of the pavement. This paper presents an analytical and experimental framework to evaluate the potential for debonding at the layer interface of asphalt concrete pavements. Computational analysis was performed to determine the critical stress and strain states in layered asphalt pavements under moving vehicle loads using the Layered ViscoElastic pavement analysis for Critical Distresses (LVECD) computer program developed at North Carolina State University. This computational analysis enables a greater understanding of the critical stress that is involved in debonding and the ways that such stress is affected by pavement design parameters and environmental conditions. In addition, a prediction model was developed that can determine the shear bond strength at the interface of asphalt concrete layers with different tack coat materials at various temperatures, loading rates and normal confining stresses. The systematic and mechanistic framework developed in this study employs the maximum shear ratio concept as a shear failure criterion and provides a tool to evaluate the effects of various loading, environmental and pavement factors on the debonding potential of asphalt pavements. The overall advantages of the mechanistic framework and approach using the LVECD analysis tool will help lead to better understanding of the debonding mechanism, proper selection of the tack coats, and economic benefit in highway pavement maintenance and rehabilitation costs.

Introducing realistic tire–pavement contact stresses into Pavement Analysis using Nonlinear Damage Approach (PANDA)

Realistic tire–pavement interface contact areas and stresses were incorporated into the Pavement Analysis using Nonlinear Damage Approach (PANDA) user interface (PUI). PANDA is a software library developed to simulate the complex thermo-viscoelastic–viscoplastic–viscodamage responses of the pavement to mechanical and environmental loads. The PUI is an interface generating a finite element representation of the pavement within PANDA. The application of realistic tire loading is necessary to calculate accurate pavement responses. The PUI incorporates a database of tire contact areas and stresses obtained from tire finite element simulations. The database includes tire interface characteristics with pavements for various applied loads, tire inflation pressures, vehicle speeds and scenarios of different rolling simulations. A parametric study was conducted to investigate the effect of simulations of tire contact stresses that match field measurements on viscoelastic and viscoplastic pavement responses. Pavement responses are greatly affected using realistic tire loading contact stresses and contact geometry as compared to simplified contact models. The impact on rutting and damage predictions cannot be ignored if reliable projections of pavement performance are to be made. This study confirms the importance of considering realistic three-dimensional contact stresses to design and analyse pavements.

A New Form of the General Solution of the Elastic Space Axisymmetric Problem in Pavement Mechanics

In order to analyze the stress and displacement of pavement, a new form of the general solution of the elastic space axisymmetric problem is proposed by the method of mathematics reasoning. Depending on the displacement function put forward by Southwell, displacement function is derived based on Hankel transform and inverse Hankel transform. A new form of the general solution of the elastic space axisymmetric problem has been set up according to a few basic equations as the geometric equations, constitutive equations, and equilibrium equations. The present solution applies to elastic half-space foundation and Winkler foundation; the stress and displacement of pavement are obtained by mathematical deduction. The example results show that the proposed method is practically feasible.

Numerical Modelling of Bubbles Formation in the Bridge Asphalt Pavement Under Gas Pressure Impact

One of the major issues of concrete bridges pavement design and maintenance is bonding between flexible bituminous layers and the deck. Any bonding failure can lead to the development of local delamination areas, which are formed as a result of the separation of the membrane sheets (insulation) from the concrete deck. This is caused by high pressure of gases accumulated between the layers leading to the formation of gas-filled bubbles. This paper discusses the research carried out in order to better understand this process of distress between pavement, insulation and concrete deck. The main objective of the presented study is the detailed structural modeling under the influence of climatic and mechanical loading. Numerical solution was obtained using Finite Element Analysis (FEA) and the calculations were performed applying Abaqus system. The ability to determine of the stress and deformation states of the bridge structure pavement opens a new way to better understand the phenomenon and to carry out the optimization of detailed technological solutions.

Computational Approach to Investigation of Crack Behaviour under Vehicular Loading of A Typical Concrete Pavement (A Case Study of Mbagathi Road in Nairobi)

Nairobi County has nearly 100% road network as bituminous roads and only 4km road network (Mbagathi Road) is concrete road. This road was a pilot project that was implemented by Kenyan Government between the years 2005 and 2007 at a total construction cost of over 400 million Kenya Shillings. The design was done based on South Africa design procedure on a 210 mm thick PJCP pavement. Performance of Plain Jointed Concrete Pavement (PJCP) depends on aggregate interlock, which is the mechanism by which loads are transferred from one slab to the adjacent one. This study attempted to use the information on load transfer mechanics in order to quantify the effect of aggregate properties to crack size as well as the propagation of any cracks formed in service. This research was undertaken in two different ways namely experimental and computer simulation. The experimental approach entailed measuring widths and depths of cracks existing in Mbagathi road, and also involved setting up concrete beams in the laboratory and loading them to failure with predetermined loads and measuring sizes of resulting cracks. On the other hand, the computational approach was verified by experimental results entailed simulating crack widths and depths with recent devised fracture models. Cracks were experimentally noticed to occur due to loading the pavement with vehicular loads bigger than safe load. Cracks generated had crack width equivalent to the measured flexural deflection and for an ideal concrete pavement crack width and crack depth exhibited an exponential relationship. It was found that vehicular loads induce stresses in concrete pavements which exceed permissible tensile stresses, hence a better understanding of the resultant cracks, as well as their propagation. This research will lead to an improvement of the design of concrete pavements in Kenyan environment.

Dynamic Analysis and Determination of Maximum Tensile Strain of Bottom Asphalt Concrete for Different Vehicle Velocities

Studying the stress, strain and deformation in pavement under traffic loads is one of the most important areas in pavement engineering. Tensile strain in the bottom of asphalt, leads to the most common type of failure (fatigue); therefore, it is an important parameter to be analyzed. In this study, the pavement structure has been analyzed and then for validation, the output in all elements and points were compared to the field results obtained from University of Pensylvania. The further studies were conducted by 3D program which indicated a good agreement with the results from field and the first finite element-based program. In static and quasi-static loadings, the maximum strain were observed exactly under the load center, while in dynamic loading, unexpectedly,themaximum value occurred behind the load center, and the distance increases by increase of vehicle velocity. This study includes the effect of load speed on tensile strain in asphalt sub-layer.

Combined effect of asphalt concrete cross-anisotropy and temperature variation on pavement stress–strain under dynamic loading

This study investigates the combined effects of asphalt concrete (AC) cross-anisotropy and temperature on asphalt pavement’s stress–strain under moving wheel loads. To facilitate this study, a dynamic Finite Element Model (FEM) of an instrumented pavement section on Interstate-40 (I-40) near Albuquerque, New Mexico, is developed in ABAQUS incorporating depth-temperature variations in the AC layer under a truck wheel loading. Cross-anisotropy in the model is defined as the ratio of horizontal to vertical modulus (n-value) of the AC. Field compacted AC cores were collected from the instrumented pavement section and tested in the laboratory to determine the n-value and viscoelastic parameters, which are incorporated in the FEM model using the User Defined Material (UMAT) interface in ABAQUS. Model is validated using field measured deflections and strains values under Falling Weight Deflectometer (FWD) test. The validated model is used for a parametric study by varying n-values of AC material under different pavement temperatures. It is observed that the horizontal tensile strain at bottom of the AC layer decreases as the n-value approaches 1.0 (isotropy). It indicates that the horizontal tensile strain decreases as the horizontal modulus of the AC increases. It is also observed that the vertical strains on top of pavement layers decreases with an increase in n-value. It indicates that increase in horizontal modulus of the AC leads to decrease in the vertical strains of pavement layers. The parametric study based on pavement temperature variation shows that horizontal tensile strain at bottom of the AC layer as well as vertical strains on top of AC, base, subbase, and subgrade are highly sensitive to temperature variation in AC layer.

Full-scale field testing on a highway composite pavement dynamic responses

A series of full-scale field tests were conducted to observe the composite pavement’s dynamic responses subjected to heavy traffic load. The tire contact pressure beneficially influences the dynamic strains and the dynamic stresses of pavement. A typical “M” shape is observed for the distribution of dynamic responses cross lane. The range of dynamic soil stress on roadbed ranges at 20–50kPa, and a non-linear model is presented for the dynamic stress attenuation along subgrade depth. Furthermore, the increasing of truck speed decreases the dynamic responses of composite pavement. This is owing to the viscoelastic property of HMA layer and the resonant frequency. At a lower moving speed, the dominant frequency of heavy truck loading is close to the dominant frequency of HMA layer. This would amplify the vibrations of pavements and consequently result in larger mechanical responses. The experimental findings would be helpful to understand the dynamic performance of composite pavement subjected to heavy traffic load.

New asphalt pavement failure criterion based on unified strength theory

This study aims to introduce an appropriate analytical method for asphalt pavement based upon unified strength theory (UST). The traditional maximum shear stress strength theory (MSST) cannot describe the marked difference between tension strength and compressive strength or variable intermediate principal stress, which significantly affects the geotechnical materials. Our studies try to find a new asphalt pavement failure criterion that considers the influence of both tension-compression strength ratio and intermediate principal stress of asphalt mixture. In order to select a suitable theory on pavement material, the UST is introduced and compared with the traditional theory. Results show that the tension-compression strength ratio of asphalt mixture, which is used as a material parameter, dramatically affects the stress and stress distribution law in pavement; the pavement stress level increases dramatically after considering the intermediate principal stresses. Therefore, the UST which considers both tension-compression strength ratio and intermediate principal stress is more in line with the material characteristics of asphalt pavement.

Stress Analysis of Simple-Supported Box Girder Deck Pavement under the Effect of Concrete Cushion

In order to study the stress distribution law of simply-supported box girder bridge deck pavement under the effect of triangular concrete cushion, finite element analysis program is used to analyze distribution regularity of stress among asphalt and cement concrete cushion at the thinnest thickness of concrete cushion and transverse slope degree under the action of eccentric load which is applied in the most critical position. The result indicates that the first principal stress in asphalt pavement, the interface normal tensile stress and interface shear stress will reduce when the cushion layer thickness and transverse slope degree increase, however, the thinnest thickness of cushion should not be less than 3 cm. Considering the total weight of structure, cushion thickness should not be too large either. The thinnest cushion thickness of simply supported box girder bridge pavement layer is recommended for 3-4cm while transverse slope for 2-3%.

Computational Approach to Investigation of Crack Behaviour under Vehicular Loading of A Typical Concrete Pavement (A Case Study of Mbagathi Road in Nairobi)

Nairobi County has nearly 100% road network as bituminous roads and only 4km road network (Mbagathi Road) is concrete road. This road was a pilot project that was implemented by Kenyan Government between the years 2005 and 2007 at a total construction cost of over 400 million Kenya Shillings. The design was done based on South Africa design procedure on a 210 mm thick PJCP pavement. Performance of Plain Jointed Concrete Pavement (PJCP) depends on aggregate interlock, which is the mechanism by which loads are transferred from one slab to the adjacent one. This study attempted to use the information on load transfer mechanics in order to quantify the effect of aggregate properties to crack size as well as the propagation of any cracks formed in service. This research was undertaken in two different ways namely experimental and computer simulation. The experimental approach entailed measuring widths and depths of cracks existing in Mbagathi road, and also involved setting up concrete beams in the laboratory and loading them to failure with predetermined loads and measuring sizes of resulting cracks. On the other hand, the computational approach was verified by experimental results entailed simulating crack widths and depths with recent devised fracture models. Cracks were experimentally noticed to occur due to loading the pavement with vehicular loads bigger than safe load. Cracks generated had crack width equivalent to the measured flexural deflection and for an ideal concrete pavement crack width and crack depth exhibited an exponential relationship. It was found that vehicular loads induce stresses in concrete pavements which exceed permissible tensile stresses, hence a better understanding of the resultant cracks, as well as their propagation. This research will lead to an improvement of the design of concrete pavements in Kenyan environment.

Finite Element Analysis of Vehicle Load Effect on Harvesting Energy Properties of a Piezoelectric Unit

To realize the goal of harvesting energy from pavement vibration on a large scale, a new type of piezoelectric harvesting units as the energy transducer has been proposed. The piezoelectric harvesting units are paved 40 mm below the asphalt, which is the same as thickness of the top layer of typical asphalt pavement in China. The spacing distance is 2200 mm, which is the same as the one between two tires of a normal vehicle. A mathematical model of the unit is deduced on Meda empirical formula and Hamilton principle and piezoelectric equations. Effects of the external vehicle load on its harvesting energy properties and pavement deformation and stress are analyzed with the finite element method. The results show that the excited voltage is linearly variation with contact pressure while the harvested electrical energy exponential varies with contact pressure. The more the contact pressure is, the larger the harvested electrical energy and the deformation and stress are. The harvested electrical energy also increases with the load frequency. At least 100 mJ of electrical energy can be collected with the proposed piezoelectric harvesting unit. It shows that the technology application of the piezoelectric harvesting energy from pavement is promising.

A Method to Estimate the Dynamic Displacement and Stress of a Multi-layered Pavement with Bituminous or Concrete Materials

In this research work, a method to estimate the dynamic characteristics of a multilayered pavement with bituminous or concrete materials is proposed. A mechanical model is established to investigate the dynamic displacement and stress of the multi-layered pavement structure. Both the flexible and the rigid pavements, corresponding to bituminous materials and concrete materials, respectively, are studied. The theoretical solutions of the multi-layered pavement structure are deduced considering the compatibility condition at the interface of the structural layers. By introducing FFT (Fast Fourier Transform) algorithm, some numerical results are presented. Comparisons of the theoretical and experimental result implied that the proposed method is reasonable in predicting the stress and displacement of a multi-layered pavement with bituminous or concrete materials. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6071

Measuring the cross-anisotropy of hot-mix asphalt

This study measures the cross-anisotropy of gyratory, kneading and field-compacted hot-mix asphalt samples of two sizes. One set of cube samples were subjected to compression through the top face and the other set through the side face. In addition, two sets of beam samples were tested for flexure stiffness using load on both the top and side faces. Results show that the side faces can sustain an average compressive stress of 0.89, 0.91 and 0.77 times of the top faces for kneading, gyratory and field-compacted cube samples, respectively. The average flexure stiffness of the side face is 0.85 times of that of the top face. For comparison, finite element model (FEM) was developed to predict pavement stress–strain under wheel load. In addition, stress–strain data from a field-instrumented pavement section on Interstate 40 in New Mexico were collected. The FEM-simulated vertical stress shows a close match with collected stress at cross-anisotropy value of 0.8.

Innovative Treatment to Winter Distresses Using a Prefabricated Rollable Pavement Based on a Textile-Reinforced Concrete

AbstractFor a fast treatment of winter distresses, a 1-cm-thick rollable pavement was developed based on a textile-reinforced concrete with short fibers. After the rollable pavement has been placed, its surface is treated with epoxy resin and chippings ranging in size from 2 to 5 mm are applied. This ensures an adequate skid resistance and low tire-surface noise. The research presented in this paper also includes results of performance tests. Firstly, the tensile strength of the rollable pavement was determined using the four-point bending test and compared with the actual stresses in real road pavements. Then, the specimens of the rollable pavement were polished using the Aachener ravelling tester. Changes in the texture and their influences on the acoustic properties, the skid resistance, the drainage, and the ravelling were studied and optimized where needed. It can be concluded that this innovative rollable pavement has high mechanical resistance and stability and very positive texture characteristics...

Moisture transport and drying shrinkage properties of steel–fibre-reinforced-concrete

Abstract Drying shrinkage has a serious impact on the structural and durability performance of concrete pavements. Shrinkage strain development and distress can only be fully understood by knowing the moisture transport and free shrinkage properties of concrete. This paper uses experiments and FE inverse analysis to determine these properties for conventional concrete (CC) and RCC reinforced with recycled-steel–fibres from tyres. Moisture diffusivity versus moisture content and a relationship between free shrinkage and moisture loss are derived. These values can be used to predict shrinkage strains and stresses in road pavements and other ground restrained slabs.

Harvesting energy from asphalt pavement by piezoelectric generator

This paper presents the way to harvest mechanical energy from asphalt pavement by piezoelectric generator. Results show that the potential energy in asphalt pavement can be up to 150 kW/h per lane per kilometre. Part of the mechanical energy can be harvested by piezoelectric transducers. The performance of seven typical transducers is examined through finite element analysis. Results show that PZT piles and multilayer, cymbal and bridge can work in asphalt pavement environment. PZT piles and multilayer have higher energy converting rate. However, the total harvested energy is small if these transducers are embedded directly in pavement. A prototype pavement generator is developed using PZT piles to increase the harvested energy. The generator can harvest more than 50 kW/h energy from the pavement under heavy traffic. 8–16 PZT piles are recommended for one generator. Round shape is suggested for the PZT piles to reduce the concentration of stress. And multilayer structure is recommended for PZT piles to decrease the electric potential of generator. The generator can be extended as sensor in the asphalt pavement, which can be used to monitor the traffic, pavement stress and temperature.

Thermal stress analysis of jointed plane in concrete pavements

Daily changing temperature causes significant thermal stress and deformations in concrete pavement with laterally fixed planes. These stresses are important parameters included in dimensioning of pavement and are significantly depended on thermal difference of plane (i.e. difference in temperature between upper and lower surface plane). In this article, thermal stresses were analysed in relationship to different diameters of dowel bars. First of all, the studies were focused on stresses distributed around the dowel bar and caused by thermal differences. The analyses were carried out using finite element method (FEM). Based on this model, temperature distribution in concrete slab was studied and next calculations for different types of dowel joints and various climatic conditions in Central Europe (Poland) were performed. Results showed that application of dowel bars with small diameters increases stresses around them. Especially harmful is concentration of stretching stresses in concrete on two sides of dowel bar. These stresses can exceed permissible values in the case of incidental strong thermal differences. The obtained results can be helpful in design of new concrete pavements and assessment of their load in countries with big temperature amplitudes.

Stress and Strain Analysis of Asphalt Pavement Impacted by Temperature and Load

Temperature and load are the major factors of road surface deformation. This paper studies how the temperature causes the road surface deformation and what the deformation trend is. A simplified model of the pavement structure and double round load loading mode were adopted respectively to analyze the stress and strain changes of road surface result of the load and the coupling effect of temperature and load. The major conclusions drew on this study are: stiffness modulus of asphalt mixture attenuates rapidly as the temperature increases, and thereby results in a significant shear deformation of asphalt pavement. At the same temperature, compressive stress decreases with the increasing of load and the deepening of the pavement structure. The influence of coupling effect of temperature and load is more significant than a single temperature or load factor. Under different coupling effect of temperature and load circumstances, the pavement structure influenced mostly by the shear stress is located 3-9cm underneath the surface.

Coupled hydro-mechanical response of saturated asphalt pavement under moving traffic load

Based on the Boit's theory, the governing equation was established to account for the response of moisture pavement. The analytical solutions were obtained through the expansion of Fourier series. Furthermore, the effects of parameters (i.e. hydraulic conductivity, traffic load velocity, drainage boundary and solid modulus) on dynamic response were investigated in terms of water-induced damage of pavement. Compared with the dry–elastic pavement, the negative normal stress in saturated asphalt pavement is concentrated beneath the traffic load, which may be a reason for a damage phenomenon in asphalt pavement. Hydraulic conductivity anisotropy plays a significant role in influencing the physical fields. Between vertical and horizontal hydraulic conductivity, the physical field almost depends on vertical hydraulic conductivity rather than horizontal hydraulic conductivity which just affects the horizontal pore-water velocity obviously. Moreover, the drained boundary evidently influences the seepage field of surface course with high permeability.