Search

Concrete pavements develop cracks with the accumulation of fatigue damage caused by the combined effect of vehicular and environmental loadings. In Mechanistic-Empirical (ME) design, the ratio of stresses to some measure of strength is used to evaluate incremental damage, which is then related to cracking. Typically, this measure is the Modulus of Rupture (MOR) of a beam made of the same material. The flexural strength is also known to vary with the thickness of the beam. However, the variation of flexural strength due the presence of eigenstresses from temperature or moisture distributions has not received sufficient attention. A non-linear fracture mechanics model demonstrated that the thickness-adjusted flexural strength can also be used for characterising the maximum elastic stress under a linear temperature distribution. However, under a non-linear temperature distribution, the material may sustain a higher or lower maximum elastic stress than the flexural strength. To model this, a practical analytical expression for the apparent flexural strength was derived and showed excellent agreement with numerical simulations as well as with a model based on equivalent elastic deformation energy. The model was used to show that the fatigue capacity under a typical axle load varies with various non-linear temperature distributions. [ABSTRACT FROM AUTHOR]

Moisture excess in granular pavement layers can decrease pavement performance leading to moisture-related distresses. The combination of trapped water and heavy traffic loads may substantially increase pore pressure and lead to shear failure if layer hydraulic conductivity is insufficient. Currently, most pavement analysis models are unable to predict pore pressure development, so the design and evaluation methods ignore this dynamic effect which may significantly underestimate the moisture damaging effect on pavements. This paper proposes the use of Biot's poroelasticity theory for modelling fully saturated unbound materials. The proposed methodology – Poroelastodynamic Finite Integration Technique (PEFIT) – was used to analyze axisymmetric multilayered pavement structures consisting of elastic and poroelastic layers. The model was verified and validated using a well-known commercial finite element solver and field pore pressure data, respectively. A sensitivity analysis was conducted by varying critical pavement design parameters. The PEFIT analysis of a three-layer pavement system with a poroelastic base layer has shown that a decrease in base hydraulic conductivity significantly increases the maximum pore pressure, especially for high-speed loads. Results also indicate substantial pore pressure and water movement in the base layer, which may induce a potential shear failure mechanism for unbound materials. [ABSTRACT FROM AUTHOR]

Continuously reinforced concrete pavement (CRCP) is a widely used alternative for heavy traffic highways due to good performance and low maintenance needs. Recently, the use of short length CRCP (50-m long slabs) has been proposed for bus stops and terminals. This paper examines the structural behaviour of cracks in short CRCP. This includes analysis of the Falling Weight Deflectometer (FWD) deflections and strain gauge measurements obtained from the full-scale test sections as well as structural modelling of the pavement. An evaluation of the influence of cracks on the FWD deflection basins collected on the experimental short CRCP pavement along with FWD data collected under the Long-Term Pavement Performance programme for conventional CRCP resulted in similar behaviour between the short and conventional CRCP. Therefore, the effects of the short CRCP transverse cracks on stresses were investigated. Three ISLAB2000 models differed by the concrete base or crack model were developed and their stress predictions were compared with field stresses. An applicability of the conventional aggregate interlock model for describing the behaviour of short CRCP was evaluated as only the continuous slab (no cracks) model was able to match the field stresses. A need for re-appraisal of the PavementME structural model is also discussed. [ABSTRACT FROM AUTHOR]

This paper studies the problem of a slab-on-grade subjected to short-duration dynamic loading. The slab-on-grade system is modelled as a viscoelastic plate resting on a generalised Pasternak foundation, which accounts for the effects of inertia, damping and shear resistance. A semi-analytical forward-solution is proposed by making use of a Hankel transform in space and a finite difference method in time. To evaluate the ability of the considered model to describe the response of slab-on-grade systems, the behaviours of several pavement sections under dynamic loading are examined. A quasi-Newton inverse analysis is employed to find the model parameters by comparing the field-measured and model-calculated responses. The results show that the generalised Pasternak model can simulate the behaviour of slab-on-grade systems with a wide range of slab and grade properties. [ABSTRACT FROM AUTHOR]

A majority of existing permeable pavement installations are related to parking lots and commercial areas with low speeds and light traffic loads. During the past two decades, a tremendous amount of progress has been made with regard to the application of permeable pavements regarding mix design, hydrologic design, water quality assessment and maintenance requirements. Review of the literature revealed, however, that there are still many important questions that must be answered before permeable pavements can be fully integrated in urban roads, especially in highways with high speeds and loads. This paper summarises the major research progress in the above listed areas and identifies research needs. Research needs are summarised under four topics: (1) structural and materials property, (2) hydrologic performance, (3) water quality and (4) maintenance. Research needs are further organised based on their immediate, short-term and long-term impact. [ABSTRACT FROM AUTHOR]

Various tests are used to characterise the strength and resilience of granular materials used in the subbase of a pavement system, but there is a limited understanding of how particle properties relate to the bulk material response under various test conditions. Here, we use discrete element method (DEM) simulations with a mechanistically based contact model to explore influences of the material properties of the particle on the results of two such tests: the dynamic cone penetrometer (DCP) and the resilient modulus tests. We find that the measured resilient modulus increases linearly with the particle elastic modulus, whereas the DCP test results are relatively insensitive to particle elastic modulus. The DCP test results are also relatively insensitive to inter-particle friction coefficient but strongly dependent on the particle shape. We discuss strengths and weaknesses of our modelling approach and include suggestions for future improvements. [ABSTRACT FROM PUBLISHER]

Functionality of concrete pavements can be restored through conventional diamond grinding (CDG) that improves ride quality and friction. Recently, an alternative diamond grinding configuration was proposed by the Institute for Safe Quiet and Durable Highway at Purdue University as part of a nationwide interest in quiet pavements. This paper discusses the field-testing of the CDG and alternative (innovative) diamond grinding as well as the pre-existing transverse tined (TT) texture at the MnROAD research facility. Acoustic properties, ride quality and friction performance of the diamond ground surfaces are compared to data obtained in the pre-existing TT surface. The initial performance of the innovative grind over a period of 3 years is also compared to that of the conventional grind and the TT surface. Test results, analysis, merits and demerits of the grinding types are also accentuated. [ABSTRACT FROM AUTHOR]

Dowel bars are used at transverse joints in concrete pavements to provide load transfer, reduce faulting and improve joint performance. However, a misaligned dowel may adversely affect the performance of a joint and cause distresses in the pavement. This paper presents development, calibration, validation and application of a finite element model for behaviour analysis of various types of dowel misalignment. The model permitted extension of the laboratory testing factorial, and the results were used to quantify the effects of concrete cover and embedment length. [ABSTRACT FROM AUTHOR]

Pavement design optimisation is an active area of research. Due to a large number of parameters, such as thickness of layers, material properties, climatic conditions, affecting pavement performance, it is usually not feasible to determine an optimal design using a trial and error approach. In order to make the design calculation computationally tractable, the process can be posed as an optimisation problem. Previous investigations in this vein have suffered from the limitations of a specific pavement analysis tool, specific design goals and specific optimisation algorithms. This paper presents a general computational framework, combining Mechanistic-Empirical Pavement Design Guide and Design Analysis Kit for Optimisation and Terascale Applications, to overcome these shortcomings. The framework's promise is demonstrated through its application to a minimum cost pavement design problem using both direct and surrogate-based (SBO) optimisation approaches. The SBO formulation is shown to achieve significant savings in required computational time with a minimal loss of accuracy in the determined optimal design. [ABSTRACT FROM AUTHOR]

An existing finite element program—ISLAB2000—was modified to allow for the analysis of horizontally restrained and unrestrained portland cement concrete (PCC) pavement slabs with partial depth cracks. To simulate a partial-depth crack, special line spring elements were added to the ISLAB2000 finite element code. Previously published relationships between spring elements stiffness and crack depth were used for formulating the element stiffness matrix of the line spring elements and to calculate stress intensity factors after solving the system of finite element equations.Several example problems of partially cracked PCC slabs subject to typical highway loadings were solved to verify this newly developed finite element model termed ISLAB2005. The impact of crack depth and base friction parameters on slabs stresses and deflections was investigated. On the basis of this analysis, ISLAB2005 was found to be a reliable tool for analysis of partially cracked pavements that are either restrained or unrestrained from horizontal movements. [ABSTRACT FROM AUTHOR]

Ultra-thin concrete overlays or ultra-thin whitetopping (UTW), are an attractive alternative to traditional practices for the rehabilitation of asphalt pavements. However, it is widely accepted that the exiting pavement should have substantial stiffness to make a UTW a rehabilitation option. This paper re-examines this hypothesis using the performance results and structural evaluation of two experimental sections in Brazil. It is shown that structural contribution of the existing pavement is important for good performance of UTW. However, it appears that the ability of the existing pavement to ensure composite action of the individual slabs in the UTW is more important than its contribution to the flexural stiffness. [ABSTRACT FROM AUTHOR]