Behzad Ghadimi

Failure analysis using acoustic and energy emission assessment of fibre reinforced polymer material performance under severe conditions

Laboratory compressive tests and acoustic emission analysis have been used to investigate the failure of pultruded fibre reinforced polymer materials after they have been subjected to temperature stress and compressive loading. The acoustic emission approach is then compared with the experimental values of energy released by each sample through the corresponded load-displacement curve. Samples subjected to severe thermal conditions showed more evidence of brittle failure mechanism. This analysis has been conducted in order to confirm the potential capacity of fibre reinforced polymer materials, known currently for their strength and lightweight but often ‘brittle’ physical characteristics, to perform under exaggerated conditions of temperature and compressive stress.

Simulation of Shakedown Behavior in Pavement's Granular Layer

While in the design of flexible pavement the significance of asphalt layers is understood, the role of granular layers supporting the asphalt layers should not be underestimated. The behavior of granular layers used in base, sub-base or subgrade layer of flexible pavement is complicated due to nonlinear elastoplastic response of materials subjected to dynamic load of traffic. Shakedown theory integrated with Mohr-Coulomb criterion is applied to simulate the response of granular layers to dynamic loading in a numerical analysis. The results of analysis is then compared to simple the results of modeling without considering shakedown effects and the conclusion is drawn.

Evaluation and validation of characterization methods for fatigue performance of asphalt mixes for Western Australia

The determination of appropriate pavement thickness using laboratory determined parameters is one of the key issues facing the road manager. Five different types of asphalt mixes were produced in laboratory to modify pavement performance mixture. The main objective of this study is to evaluate the characterization methods for fatigue performance of asphalt mixes to Western Australia road. In this study, laboratory test for indirect tensile modulus, dynamic creep, wheel tracking and aggregate gradation tests were taken to analyze each asphalt mixtures for a design traffic road. The results and analysis showed that AC20-75 asphalt mix blow is the most effective and efficient in pavement performance than the other asphalt mixes. AC14-75 was the second in rank to strengthen and durability of asphalt pavement. All asphalt mixes in this study can be used to strength and stable the overall stiffness of pavement, and modification rank can be described as AC20-75 Blow > AC14-75 Blow > AC14-50 Blow > AC7-50 Blow > SMA7-50 Blow in this research.

Developing Master Curves, Binder Viscosity and Predicting Dynamic Modulus of Polymer-Modified Asphalt Mixtures

The complex moduli relationship related mixture moduli to temperature and time rate of loading has been an integral part of several mechanistic-empirical (M-E) design procedures used throughout of the world. Seven asphalt concrete mixtures of different types of polymer modified binders (PMB) were produced in a laboratory to modify performance of asphalt mixture. The main role of this research is to evaluate the influence of these polymer modifiers on the pavement performance of asphalt mixture with the dynamic modulus, |E*| of hot-mix asphalt (HMA) mixture indicator in a laboratory test for Mainroad Western Australia and Fulton Hogan. In this study, the influence of temperature, loading frequency, and confining pressure on the dynamic characteristic of asphalt mixture were analysis, master curves of dynamic modulus of HMA mixtures were developed and datas were interpreted. Results showed that AC10 5.7% A35P (EVA) M7 B5, AC10 5.7% C450 M10 B5 and AC10 Multi 600/700 M5 B4 mixes method were the more efficient and effective in all categories of asphalt performance measures for strength and durability of HMA as compared to others polymer modifiers. A very good correlation (R 2 = 1) was found for each polymer modifier. This suggested that laboratory test using a various temperatures and loading frequencies can improve pavement mix design, lab and field control and assurance. A strong correlation between binder viscosity and temperature (R 2 = 1) for polymer modified asphalt mixture.

Distress Identification, Cost Analysis and Pavement Temperature Prediction for the Long-Term Pavement Performance for Western Australia

Collection and analysis of pavement distress data is a significant component for effective long-term pavement performance. Accurate, consistent, and repeatable pavement distress types evaluation can reduce a tremendous amount of time and money that has been spending each year on maintenance and rehabilitation of existing pavement distress. The main objective of this study is to identify and quantify of surface distress in a given segment of pavement, to perform details distress rating, to predict pavement temperature and cost analysis of individual pavement distress on heavily urban roads in Western Australia (WA). Field survey were conducted from three regions in WA and two approached were used to evaluate and analysis the pavement distress. First, the probabilistic network Marov-Chain Process method was used to predict the cost analysis for individual asphalt concrete surfaced pavement distress. Second, Statistical Downscaling Model (SDSM) was used to predict pavement temperature for asphalt concrete surface pavement. Meteorological data were collected from Perth, Kalgoorlie, and Albany region in WA, and data were used to develop and validation of the model. Different types of pavement distress level were identified and color photograph illustrated the asphalt concrete surfaced pavement. Results were performed and analysis. Results from this study will be useful resource to Main Roads Western Australia, Western Australia State Highways (WASH), and other pavement related users including to the National Highway System (NHS). In addition, results can be used for pavement management systems (PMSs) purpose.

The Prediction of Contaminant Transport through Soil: A Novel Two-Dimensional Model Approach

The transport of contaminants has been a problematic issue for many years, mainly due to the adverse impact of the contaminants on the quality of groundwater. In order to analyse this, this study has developed a prediction model that allows the early detection of possible contamination. Firstly, the paper introduces the concept of the modelling of contamination transport through a soil matrix. Then it presents a two-dimensional Convection-Dispersion Equation (CDE) for contaminant transport in a soil matrix. This includes the investigation of different reaction coefficients and time-dependent inlet boundary conditions, from which a numerical solution is derived. The study also verifies recent previous work in this area through the use of numerical programming. The results for soil contamination in two dimensions are presented in this research.

Effects of Geometrical parameters on Numerical Modeling of Pavement Granular Material

Numerical modeling of the granular pavement materials is one of the modeling approaches which can be used to predict material response to specific loading conditions. This modeling is dependent on many factors and variables and includes assumptions for material behavior, loading conditions, geomechanical properties and geometrical parameters. In this study in-depth research has been undertaken to determine the sensitivity of geometrical parameters on pavement numerical modeling. Geometrical parameters are all those parameters that can be used to define a numerical model including layer thickness, meshing system and nature of the model (2D or 3D). In this study a layered granular pavement has been modeled through ABAQUS which is a general finite element program. The results have been compared with layered elastic theory by CIRCLY and KENLAYER. This study will deal with three kinds of modeling being 2D axisymmetric, 2D plain strain and a complete 3D model. In each of these three models, the influence of layer thickness, elements type and mesh density has been investigated. The results have been presented, compared and discussed in order to identify the most influential parameters.

Pavement Materials Characterization of Hot-Mix Asphalt Mixes in Western Australia

The use of deep strength asphalt materials characterization to construct and restore the heavily urban roads where damage has been induced is rapidly grown in Western Australia. Five different types of asphalt mixes were produced in laboratory to modify pavement performance mixture. The main role of this research is to evaluate the pavement materials characterization for Western Australia road. In this study, laboratory test for tensile strength, resilient modulus, wheel tracking, binder contents, Marshall Compaction, and air voids contents test were taken to analyze each asphalt mixtures. The results indicated that AC20-75 and AC14-75 asphalt mixes blow were in a good pavement performance as compared to other asphalt mixes. For a mix design purposed, all the asphalt mixes that are used in this study can strength and stable the stiffness of pavement that is notable, and the modification effect rank can be described as AC20-75 Blow > AC14-75 Blow > AC14-50 Blow > AC7-50 Blow > SMA7-50 Blow in this research.

A comparison between effects of linear and non-linear mechanistic behaviour of materials on the layered flexible pavement response

Modelling granular pavement materials has a significant role in the pavement design procedure. Modelling can be through an experimental or numerical approach to predict the granular behaviour during cyclic loading. The current design process in Australia is based on linear elastic analysis of layers. The analysis is performed through a well-known program CIRCLY which is applied to model bound pavement material behaviour. The KENLAYER is one of the common pavement software models used for pavement design in the United States which performs non-linear analysis for granular materials. Alternatively, a general Finite Element program such as ABAQUS can be used to model the complicated behaviour of multilayer granular materials. This study is to compare results of numerical modelling with these three programs on two sample pavement models.

A comparison of implementation of linear and nonlinear constitutive models in numerical analysis of layered flexible pavement

It is generally accepted among pavement engineers that the granular layers in flexible pavement behave in a nonlinear mechanical way. Existing literature documents different constitutive equations to model this nonlinearity. This paper compares four well-known constitutive models: linear elastic, K−θ, Uzan–Witczak and Lade–Nelson. In the first stages of numerical simulation, three static linear elastic models were constructed in CIRCLY, KENLAYER and ABAQUS and the results of the analysis were compared with one another. Following this, three-dimensional models were constructed in ABAQUS, and the four constitutive models were implemented for use in the finite-element model. Three sets of material parameters were considered for the analysis. The results calculated from each model were presented and compared and consisted of the following: surface deflection under loading wheels, tensile strain at the bottom of an asphalt layer, and vertical strain and vertical stress at the top of the subgrade layers. The development of the elastic modulus and vertical stress in the base layer was also investigated and the contours of the vertical elastic modulus are presented.