Fatigue Life Of Asphalt Pavement Research Articles

Study on self-healing performance of microcracks in SBS/waste rubber powder composite-modified asphalt based on molecular dynamics simulation

The internal microcracks in asphalt materials can heal spontaneously under suitable conditions, and understanding the characteristics of the self-healing behavior of asphalt materials is crucial for evaluating the fatigue life of asphalt pavements. In this paper, a molecular model of modified asphalt microcracks was created by introducing modifier molecules into the virgin asphalt model, and the self-healing process of the asphalt microcrack model under different healing conditions was investigated, which revealed the effects of modifier materials and healing temperatures on the healing performance of asphalt. The results show that the effect of healing temperature on asphalt healing performance is more significant than the modifier material, the relative concentration of molecules at the microcrack healing and the healing temperature is positively correlated; asphalt material healing free volume fraction with the increase in healing temperature gradually increases, the incorporation of modifiers can reduce the free volume fraction growth caused by high-temperature healing, improve the healing stability of modified asphalt. The asphalt ductility specimen crack healing test shows that when the healing temperature exceeds 45 ℃, there is a decreased increase in self-healing rate; taking into account the high-temperature healing is easy to make the asphalt material produce permanent deformation, this paper determines the optimal healing temperature in the vicinity of 48 ℃. The research results have certain reference and application values for asphalt pavement damage repair.

Behaviours of geogrid-reinforced asphalt pavement over a localized void under cyclic loading

A set of large-scale physical model tests were performed to investigate the performance of unreinforced and glass fibre geogrid-reinforced asphalt pavement under the development of a void in the subgrade. Traffic loadings were simulated with repeated sinusoidal loadings of different amplitudes. The formation of the void was simulated using a novel displacement control device between loading cycles. The accumulative permanent deformation of the asphalt pavement, the composite resilient modulus and dissipated energy were presented and analysed. It was found that the inclusion of geogrid greatly improved the fatigue life of asphalt pavement, and the stronger the geogrid, the greater the improvement if a void was formed below the asphalt layer. After forming the void, the composite moduli of the pavements increased compared with that during the first cyclic loading stage (without the void) and seemed to be not much affected by the geogrid type. The effect of cyclic loading level on the composite modulus was not significant. The inclusion of geogrid in asphalt had a limited effect on the dissipated energy in the pavements with and without voids. The dissipated energy increased with the cyclic loading amplitude.

Response Prediction of Asphalt Pavement in Cold Region with Thermo-Hydro-Mechanical Coupling Simulation

Although the theoretical pavement structure design method (TPSDM) is widely used for designing asphalt pavements in Japan, it still exhibits certain limitations, such as not considering the variation in moduli of the base and subgrade layers due to water contents, freeze–thaw action, and stress states. This study aims to enhance Japanese TPSDM’s accuracy by considering variations in the resilient modulus of environmental impacts, pavement materials, pavement structure, and traffic load actions to accurately calculate the mechanical responses and predict pavement fatigue life. Firstly, the study develops a 3D Thermo-Hydro-Mechanical (THM) model using the finite element method (FEM) to investigate temperature and moisture distributions of the pavement with time. Then, based on the numerical results of the moisture, temperature, and stress state obtained from the THM analysis, the constant resilient modulus of the base and subgrade layers in the Japanese TPSDM is replaced with a resilient modulus that considers the stress state and the combined effects of water content fluctuations and freeze–thaw action. Finally, the fatigue life of the pavement is calculated based on the obtained mechanical response in THM analysis. The reliability and validity of the proposed fatigue life prediction method are well verified by comparing the calculated with the actual pavement fatigue life. Results indicate that the modifications improve the Japanese TPSDM by considering the environmental impacts, traffic load actions, pavement materials, and pavement structure, thereby improving the accuracy of predicting the fatigue life of asphalt pavements, particularly in cold regions.

Influence of Axle Load and Asphalt Layer Thickness on Dynamic Response of Asphalt Pavement

Based on the test data of vehicle load test on asphalt pavement, the significance of dynamic response index of different asphalt pavement to axle load change of single and double rear axle trucks is analyzed. The changes of horizontal strain at the bottom of asphalt layer, vertical compressive stress at the top of subgrade, and vertical displacement of transition layer and bottom compressive stress before and after laying of middle and upper layers are revealed. The test results show that reducing the thickness of asphalt layer or increasing the vehicle axle load can lead to the more unfavorable stress-strain distribution in asphalt pavement under driving load. The influence of the fluctuation of truck axle load or asphalt layer thickness on the stress-strain distribution in asphalt pavement varies with the type of pavement structure, pavement response index, vehicle driving speed, vehicle type, and the horizon of the measuring point. The transverse strain at the bottom of the asphalt layer is more affected by the axle load and the thickness of the asphalt layer than the longitudinal strain at the bottom of the asphalt layer. The measured value of the dynamic response index of the semirigid asphalt pavement is more affected by the axle load than that of the inverted asphalt pavement. However, the measured value of the dynamic response index of the semi-rigid asphalt pavement is less affected by the thickness of the asphalt layer when the thickness of the asphalt layer changes within a certain range. The tensile strain part of the longitudinal strain at the bottom of the asphalt layer and the compressive strain part of the transverse strain at the bottom of the asphalt layer are greatly affected by the thickness of the asphalt layer. The sensitivity of fatigue life of asphalt pavement of inverted structure to driving speed and axle load is less than that of semirigid structure. The research results can provide reference for the analysis of the asphalt pavement disease mechanism and provide guidance for asphalt pavement structural design and service life analysis.

Evaluation of climate effect on resilient modulus of granular subgrade material

This study examines the effects of freeze-thaw actions and the concurrent seasonal fluctuations in water content, named as climate effect in this study, on the resilient modulus of subgrade materials to evaluate their mechanical behavior in cold regions. A series of suction-controlled resilient modulus tests on subgrade materials with variant freeze-thaw, wheel loads, and water contents conditions were conducted using a newly developed test apparatus. Test results were used to construct a simple model to estimate the climate effect on the resilient modulus by considering the synergistic effects between water content and freeze-thaw. Besides, this study calculated the fatigue life of eight local flexible pavement projects with variant subgrade layer moduli considering climate effect by combining the newly proposed model and long-term in-situ measured data. Results proved that climate-related degradation of the subgrade materials decreases the fatigue life of asphalt pavements in cold regions.

Understanding asphalt binder cracking characterization at intermediate temperatures: Review and evaluation of two approaches

Accurate characterization and proper selection of asphalt binder can prolong the fatigue life of asphalt pavements. The objective of this study was to evaluate the linear amplitude sweep (LAS) test and the binder fracture energy density (BFE) test using a broad range of asphalt binders with a particular emphasis on the identification of appropriate failure definition. Three unmodified binders and three modified binders were investigated. LAS test results revealed that the failure criteria in the existing specification (35% reduction in G*sinδ and peak shear stress) did not capture the improved performance expected from modified binders whereas the peak stored pseudo strain energy (PSE) failure criterion did. This could be attributed to the larger strain levels that binder samples undergo before the instant of failure defined by the peak stored PSE. Fracture energy density measured with the BFE test on fractured specimens clearly distinguished between unmodified and modified binders. It was concluded that binder response can influence the outcome of performance comparison parameters. For comparable binder types, binders with a more ductile behavior may exhibit a more strain tolerant response in the LAS test whereas stiffer binders appeared to show a more fracture tolerant response in the BFE test.

A mechanistic framework for tensile fatigue resistance of asphalt mixtures

Fatigue life is one of the most critical factors for asphalt pavement design, which is directly affected by the fracture properties of asphalt mixtures. This study aimed to present a mechanistic framework to determine the Paris’ law parameters A′ and n′ of asphalt mixtures and fatigue life of asphalt pavements. The dynamic modulus test and indirect tensile (IDT) test results were obtained from Texas Data Storage System (DSS) to evaluate the linear viscoelastic properties and fracture properties. Modified Griffith crack criterion in tension was used to determine the damage density rate and pseudo J-integral of macrocracks appeared in the post-peak phase of the IDT test, and the damage density with time was shown as a sigmoidal shape from microcracking initiation. The Paris’ law parameters were then computed using the regression analysis in the macrocracking stage. It was shown that the fracture resistance of asphalt mixtures could be characterized using n′, and a smaller value of n′ indicates a better fracture resistance. The mode-I fatigue life equation for reflection cracking in asphalt pavements was also proposed based on the J-integral from the finite element model and Paris’ law parameters, which shows that the empirical fatigue life transfer function could also be determined from actual material properties and pavement structural boundary conditions.

АНАЛІЗ ЕКСПЕРИМЕНТАЛЬНИХ ДОСЛІДЖЕНЬ ФІЗИКО-МЕХАНІЧНИХ ВЛАСТИВОСТЕЙ ЕПОКСИАСФАЛЬТОБЕТОНУ ДЛЯ ЙОГО ЗАСТОСУВАННЯ У ЯКОСТІ МОСТОВОГО ПОКРИТТЯ НА АВТОМОБІЛЬНИХ ДОРОГАХ

Introduction. This paper considers the issue of improving the quality of coatings on road reinforced concrete, reinforced concrete bridges or metal bridges with orthotropic slab. The constructive decisions of increase of working capacity and fatigue durability of asphalt concrete coverings are offered. The results of the analysis of experimental researches of physical and mechanical properties of epoxy asphalt concrete are given. The efficiency of epoxy components in asphalt concrete mixtures, which significantly improve the physical and mechanical properties of bitumen, is shown. According to the results of experimental laboratory tests, a comparative analysis of the properties of epoxy asphalt concrete and source asphalt concrete on viscous and rarefied bitumen is given. Also, the influence of the duration and temperature of curing of epoxy components on the properties of epoxy asphalt concrete was analyzed. Problem statement. In today’s conditions of high-speed intensive traffic, high traffic loads and adverse weather and climatic factors that occur in our country, increasing the durability of pavements on bridges to increase service life and reduce costs associated with maintenance, requires special attention. One of the effective ways to improve the quality and durability of asphalt pavements on road bridges is the modification of bitumen by using as the main material thermosetting polymer additives, in our case – epoxy components (epoxy resin and its hardener). Objective. The purpose of the analysis of experimental studies of physical and mechanical properties of epoxy asphalt concrete is to study the possibility of its use as a pavement on highways. As well as confirmation of efficiency in solving the problem of achieving increased fatigue life of such coatings at different load frequencies by increasing track resistance, strength, crack resistance and at the same time solving no less important issue to minimize the cost of repair and construction work during bridge operation. Materials and methods. Asphalt concrete coverings on orthotropic or reinforced concrete slab of the carriageway of the bridge with improved physical and mechanical properties due to the use of thermosetting polymer additives as a bitumen modifier. Results. The analysis of experimental researches of physical and mechanical properties of epoxy asphalt concrete is carried out and efficiency of its application for improvement of quality of coverings on road bridges and increase of their durability is defined. A set of studies was conducted to compare the properties of epoxy asphalt concrete and source asphalt concrete on viscous and rarefied bitumen. Conclusions. To increase the fatigue life of asphalt pavements on road bridges in modern conditions of high traffic intensity in our region with a wide range of operating temperatures, it is necessary to develop new solutions for the use of building materials. That is why the study of physical and mechanical properties of asphalt concretes improved by thermosetting polymer additives in order to determine their true effectiveness in improving track resistance, strength and crack resistance of coatings based on them is an urgent issue today. The use of epoxy-asphalt concrete coating on orthotropic or reinforced concrete slab of the carriageway of the bridge requires special attention in establishing the optimal duration and curing temperature of epoxy components, which can dramatically affect its physical and mechanical properties and determine the cooking technology. Keywords: epoxy asphalt concrete, epoxy asphalt concrete mixture, physical and mechanical properties of epoxy asphalt concrete, composition of epoxy asphalt concrete mixtures, epoxy resin, road bitumen, modification of bitumen, properties of bitumen, durability of paving.

Evaluating the effect of amine-based anti-stripping agent on the fatigue life of asphalt pavements

ABSTRACT Aggregate-binder adhesiveness is a property that can affect the service life of asphalt pavements. In order to reduce the effects of the loss of adhesion between aggregates and binders over time, lime or amine-based anti-stripping agents are commonly used. The objective of this paper is to evaluate the impact of using an amine-based anti-stripping agent on the fatigue life of asphaltic pavements. Stiffness characterisation, the Simplified Viscoelastic Continuum Damage model, and the software FlexPAVE™ were used. Two different layered structures were analysed: one with a 0.10 m asphalt layer thickness, and another with a combination of two 0.05 m asphalt layers, with the same 0.10 m total asphalt layers thickness. The 10 years fatigue simulation was considered with 1,000,100 total ESALs traffic volume, single wheel loading of 40 kN, traffic speed of 60 km/h, and constant temperature of 20°C. It was concluded that mixtures with anti-stripping agent and/or granitic aggregate showed better fatigue behaviour than mixtures with neat binder and/or phonolitic aggregate. All investigated pavements showed bottom-up predicted crack initiation. It is more recommended to use the mixtures with amine-based anti-stripping agent on the bottom asphalt layer and mixtures with neat binder on the top layer.

Fatigue evolution characteristic and self-healing behaviour of asphalt binders

ABSTRACT The self-healing ability of asphalt material has a significant effect on improving fatigue life of asphalt pavement. The objective of this paper was to investigate the stage characteristics of fatigue damage of asphalt binder and its associated self-healing behaviours. Firstly, the rheological behaviour and fracture surface morphology were discussed to investigate the fatigue evolution characteristics of asphalt binders. Secondly, an effective method for interpreting the self-healing capability of asphalt binder at different fatigue stages was proposed by conducting fatigue-healing-refatigue tests and Fourier transform infrared spectroscopy analysis. Finally, the effect of temperature on the self-healing properties of different aging asphalt binders at different fatigue damage stages was explored. The results show that the stage characteristics of fatigue damage of asphalt binders could be distinguished effectively by correlating complex shear modulus with ratio of dissipation energy change under load time history. The fatigue cracking morphologies of asphalt binders under cyclic shear loading are susceptible to the aging degree of asphalt binder. An index associated with initial dissipative energy and number of cycles could effectively evaluate the self-healing properties of different aging asphalt binders. After the occurrence of macrocracks, the mechanical properties of asphalt binder cannot be completely restored by increasing the temperature.

Fatigue performance assessment of recycled tire rubber modified asphalt mixtures using viscoelastic continuum damage analysis and AASHTOWare pavement ME design

Improving fatigue cracking resistance of asphalt mixtures is an important issue that concerns roadway agencies, public and industry. There are various, well-established methods for improving the material characteristics, such as polymer modification methods. Recycling/reusing scrap tire rubber in asphalt pavements has also been an interest of engineers. As such, many different methods of scrap tire rubber (herein called crumb rubber) modification alternatives are being developed. This study focused on a comparative evaluation of the fatigue cracking resistance of various base and recycled tire rubber modified asphalt mixtures, including the relatively new and innovative devulcanized rubber (DVR), crumb rubber terminally blend (CRTB), crumb rubber wet process (CRWET), original/base PG58-28 and softer PG58-34 binders, by using Push-Pull Viscoelastic Continuum Damage (PP-VECD) analysis and AASHTOWare Pavement Mechanistic Empirical Design (Pavement ME) software. The results of the study revealed that rubberized asphalt mixtures provided better fatigue lives than the base and softer binders did. Especially, DVR mixtures outperformed at high strain levels, implying they can be used for heavy traffic roads to enhance the fatigue life of asphalt pavements. Both PP-VECD and Pavement ME produced results that showed similar trends.

Response Analysis of Asphalt Pavement under Dynamic Loadings: Loading Equivalence

This paper establishes the equivalent relationships between the half-sinusoidal load, triangular load, vertical stepwise load, and moving traffic load. The governing equation was established for analyzing the dynamic responses of pavement, and half-sinusoidal load, triangular load, and vertical stepwise load functions were transformed into Fourier series expressions. The partial differential governing equations were simplified as ordinary differential equations and the analytical solutions were obtained. Further, the solutions were validated through comparing the theoretical results with numerical simulated results. Calculation results revealed that, for unchanged load periods, increasing the amplitudes of the three loads by 1.06, 1.31, and 1.35 times can better simulate the moving traffic loads. For unchanged load function amplitudes, increasing the function periods by 1.07, 2.23, and 2.1 times (for half-sinusoidal, triangular, and vertical stepwise loads, resp.) can improve the simulation performance. The fatigue life of asphalt pavements under the moving traffic load agrees with that of the three load simulations, indicating that the fatigue life of asphalt pavements is only associated with the load amplitude but not the load patterns.

Investigating the effects of loading, mechanical properties and layers geometry on fatigue life of asphalt pavements

AbstractIn this paper, fatigue life, crack growth trajectory, and stress intensity factors of top‐down and bottom‐up cracks have been investigated in a multilayered asphalt pavement using numerical method. Finite element models, Paris law, and maximum tangential stress criteria were used to determine the effects of vehicle position, thickness, and stiffness of layers on fatigue life of pavements. The results show that the minimum fatigue life of pavements with top‐down crack occurs when the wheels are symmetrically located relative to the crack plane. On the other side, in pavements with bottom‐up crack, it occurs when the front tire located on top of the crack. Moreover, the result reveals that the top‐down crack grows slower than bottom‐up crack. Also, the surface layer's stiffness has the most effect on fatigue life of pavement.

Nonlinear genetic-base models for prediction of fatigue life of modified asphalt mixtures by precipitated calcium carbonate

Fatigue cracking is the most important structural failure in flexible pavements. The results of a laboratory study evaluating the fatigue properties of mixtures containing precipitated calcium carbonate (PCC) using indirect tensile fatigue (ITF) test were investigated in this paper. The hot mix asphalt (HMA) samples were made with four PCC contents (0%, 5%, 10%, and 15%), and tested at three different testing temperatures (2°C, 10°C and 20°C) and stress levels (100, 300, and 500 kPa). Due to the complex behaviour of asphalt pavement materials under various loading conditions, pavement structure, and environmental conditions, accurately predicting the fatigue life of asphalt pavement is difficult. In this study, genetic programming (GP) is utilised to predict the fatigue life of HMA. Based on the results of the ITF test, PCC improved the fatigue behaviour of studied mixes at different temperatures. But, the considerable negative effect of the increase of the temperature on the fatigue life of HMA is evident. On the other hand, the results indicate The GP-based formulas are simple, straightforward, and particularly valuable for providing an analysis tool accessible to practicing engineers.

A mechanistic-empirical model for predicting top-down fatigue cracking in an asphalt pavement overlay

Climate, pavement structure, traffic and material properties were identified and incorporated into a new mechanistic-empirical model to predict top-down cracking in an asphalt pavement overlay. The shear strain at the edge of the tyre was determined as a critical pavement structural response for initiating top-down cracking. The horizontal failure strain, dynamic modulus and shear strain at the edge of the tyre were incorporated in the model for characterising the fatigue life of asphalt pavements. The model was calibrated and verified using the data collected nationwide and is recommended to supplement the current models in the mechanistic-empirical pavement design guide (MEPDG). To mitigate top-down cracking in the asphalt pavement overlay, it is recommended to design an asphalt mix with relatively a higher horizontal failure strain value to reduce the shear strain response along the edges of the tyre.

Analysis on the Fatigue Properties of Semi-Rigid Base Asphalt-Pavement Structures With Horizontal Interfacial Cracks

Abstract To find out the impact of horizontal interfacial cracks on the fatigue life of a semi-rigid base asphalt pavement, in this research, based on fracture mechanics, we first prefabricated four horizontal cracks (0, 30, 60, and 90 mm in length) and placed them between the semi-rigid base and the asphalt surface. Then we tested their bending strength and fatigue life, respectively. The results show that the existence of interfacial cracking has a strong impact on both the bending strength and fatigue life of the asphalt pavement. Compared with the specimen without an interfacial crack (0 mm in length), the bending strength of the specimens with horizontal interfacial cracks (30, 60, and 90 mm in length) decreases by 7.4 %, 14.7 %, and 20.6 %, and the fatigue life declines by 16.5 %, 29.2 %, and 39.7 %, respectively. Horizontal interfacial cracks result in the discontinuity of the whole pavement structure and the change of the stress state in the pavement. Also, cracking develops faster under fatigue loading conditions, so the pavement strength is further reduced and the fatigue life shortened.

Performance evaluation of using electric arc furnace dust in asphalt binder

Electric arc furnace dust (EAFD) is one of the harmful by-products of steel manufacturing industry which contains elements such as Cr, Pb, Zn, Cu, and Cd. These elements are emitted after charge melting in an electric arc furnace. The results of leaching tests demonstrate that the amount of these elements in EAFD exceeds the established limits. To deal with this problem, EAFD can be used as an alternative material in asphalt mix production which improves fatigue life. A large amount of investments are spent on the road maintenance and a significant portion of these investments is assigned to repair cracks caused by iterative traffic load and freeze-thaw cycles. The potential of asphalt self-healing, the ability of recovering mechanical characteristics, aims in improving fatigue life of asphalt pavement as well as reducing energy consumption and environmental side effects. Mastic asphalt is a material with self-healing capability. This paper proposes an effective and efficient treatment which utilizes EAFD as filler in the asphalt mixture. Accordingly, the performance of the fatigue and self-healing potential in the mastic along with two common fillers including Granite and hydrated lime are compared through a time sweep test with/without rest period using a DSR device. Results show that asphalt mastic containing EAFD filler has much better self-healing and fatigue performance than those containing Granite filler. Consequently, using this filler in asphalt mixture decreases environmental side effects in addition to manufacturing cost reduction and improving economic aspects of asphalt production. Moreover, the environmental aspects of using EAFD in asphalt binder are investigated and the result of leaching test indicates that pavements constructed by EAFD has no threat for ground and surface waters. For monitoring the amount of pollution leaching from asphalt mixture containing EAFD into flowing water, Toxicity Characteristic Leaching Procedure (TCLP) was investigated. TCLP Results showed that the amount of heavy metals for all of these samples are lower than the regulatory levels.

Fatigue Life of Asphalt Pavements on Bridge Decks

Pavement is one of the basic elements of a bridge structure. In Europe and Poland pavements for engineering objects are made in the asphalt technology. Requirements for ensuring the sustainability of the entire object also refer to pavement. Fatigue life is one of the parameter that must be satisfy but there is no requirements connected with it. It is directly related to the stresses and strains which occur in the pavement. Based on a state of art and using calculation results of software with finite element method (FEM) the strains in characteristic points of the bridge pavement were presented. Strains in pavements on the soil, concrete and steel deck were compared. One of the classic and one of the modern criteria for fatigue life were described. Calculation models for fatigue life of asphalt pavement does not classify separately bridge pavements. A typical technology and materials used in the bridge deck pavements were presented. Fatigue life of asphalt bridge pavements were estimated. The analysis of the results and evaluation of the adequacy of fatigue life models were made.

Special Issue on Recent Advances in Constitutive and Numerical Methods for Sustainable Civil Infrastructures

This special issue of the International Journal of Geomechanics contains 10 papers that cover numerical and experimental investigations on various aspects of sustainable civil infrastructures. The topics include the self-healing capability of asphalt, cracking and fracture of asphalt pavement and portland cement concrete, soilimprovement techniques (including compaction and vertical drains), and various foundation systems. There are two papers on asphalt. The self-healing of asphalt mixtures can extend the fatigue life of asphalt pavement. Huang et al. developed a method based on fuzzy evaluation and the analytic hierarchy process for evaluating the self-healing capability of asphalt mixtures. The feasibility and effectiveness of the method were validated by a case study. To understand the mechanisms of material failure is essential for the design and construction of sustainable civil infrastructures. Chen et al. proposed a multiscale numerical modeling approach to analyze the distress of asphalt pavement on steel bridge decks and applied the approach to a case study. Their results highlighted the importance of bridge structure and pavement evenness in the distribution of pavement cracks. One paper focuses on concrete fracture and damage. Xu et al. investigated the spallation failure of fiber-reinforced concrete slabs under impact loading. Their numerical simulations showed that fibers can remarkably improve the tensile strength of concrete slabs and effectively limit the initiation and propagation of cracks. Soil improvement is an important element of sustainable civil infrastructures. Three papers are related to soil-improvement techniques, including compaction and vertical drains. Nie et al. presented an integrated theoretical and case study on anomalous data detection for roller-integrated compactionmeasurement. Their results showed that the proposed bidimensional anomalous data-identification method rendered a more accurate correlation, whereas the proposed neighbor-weighted estimation method improved the precision of compaction evaluation. Two papers are related to vertical drains. Azari et al. applied an elastic–viscoplastic model to model soft soil improved with vertical drains and compared their simulation results with field measurements. Their results showed that the distribution of the overconsolidation ratios in the disturbed zone greatly influenced the viscoplastic strain rates, creep strain limits, and consolidation. Parsa-Pajouh et al. evaluated the efficiency of several proposed formulations for plane-strain modeling of vertical drain-assisted consolidation through an integrated numerical and experimental investigation. By comparing the predicted and measured pore pressures in well-controlled laboratory tests, the advantages and disadvantages of these formulations were discussed. The remaining four papers deal with foundation systems. A better understanding of soil–structure interaction can lead to optimized foundation design and construction, which increase the sustainability of many civil infrastructures. Zhou and Dai presented a new strut-and-tie model for the analysis of force distribution among piles, pile caps, and superstructure components, including struts and ties. Through two case studies, they demonstrated the effectiveness and accuracy of their model. Farouk and Farouk examined the effect of a superstructure’s rigidity on the contact stress and differential settlement for plane two-bay frames. They found that the rigidities of walls and slabs have significant effects on the resultant average contact stresses and the maximum settlements under the footings, which affect the differential settlements. They provided new charts and equations for calculating the average contact stress and maximum settlements under the inner and outer footings for plane two-bay frames. Zhang et al. developed a numerical model to investigate the working mechanism of pervious concrete piles. Their model was validated by a case study. Their results showed that pervious concrete piles can reduce foundation settlement caused by their high stiffness and permeability and, hence, are particularly suitable for reinforcing foundations with low bearing capacity and soils with poor permeability. Yang et al. conducted a numerical investigation on the load-displacement behavior of a reinforced strip footing using a double-yield model. The effects of various parameters, such as burial depth, reinforcement length, and arrangement of two reinforcement layers, were studied. Their results showed that the load-displacement behavior of strip footings simulated with the double-yield model is more realistic than that with the Mohr-Coulomb model, and the optimal burial depth and length of reinforcement obtained from their study agreed well with values reported by previous investigators.

Estimating Truck Aggressiveness Using a Multilinear Fatigue Model and a Viscoelastic Pavement Model

AbstractTo increase freight efficiency, trucks are allowed to transport heavier loads without adding extra axles. The impact of this practice on infrastructure damage needs to be evaluated. This involves evaluating the fatigue life of asphalt pavements under multiple axle configurations. In mechanistic pavement design, the asphalt thickness is generally determined using a fatigue model calibrated in the laboratory by applying a continuous sinusoidal signal with different strain levels. The classical fatigue relationship gives fatigue life as a function of the strain level. However, results from literature show the influence of the loading wave shape on the fatigue life of bituminous mixtures. Real loading signals under multiple axle configurations are more complex in shape than sinusoidal pulses. Moreover, real strain signals have different shapes in the longitudinal and transverse directions. This paper presents an approach using a multilinear fatigue model that takes into account the shape of the loadin...