Mehrtash Soltani, Ph.D

In recent years, vehicle demographics have changed to include a relatively large proportion of light trucks, such as pickups, vans and sport-utility vehicles. It is found that several types of guardrail systems, including the G4(2W) guardrail system, are unable to redirect the pickup trucks to roadway safely. Therefore, in this study, several options are considered; they include improving the splice connections and adjusting the guardrail height and the post spacing to improve the performance… Show more

In recent years, vehicle demographics have changed to include a relatively large proportion of light trucks, such as pickups, vans and sport-utility vehicles. It is found that several types of guardrail systems, including the G4(2W) guardrail system, are unable to redirect the pickup trucks to roadway safely. Therefore, in this study, several options are considered; they include improving the splice connections and adjusting the guardrail height and the post spacing to improve the performance of this system. The G4(2W) guardrail system is modelled in LS-DYNA and validated with a previous full-scale crash test conducted by the Texas A&M Transportation Institute. A parametric study based on the results of the LS-DYNA crash simulation according to Length of Need test 3-11 and 3-10 is conducted to investigate key factors of guardrail systems, including the splice configuration, the post spacing and the guardrail height. The purpose of this study is to find a model that satisfies the requirements of Test Level 3 outlined in Manual for Assessing Safety Hardware (MASH)'s criteria. Show less

Fatigue is a major distress mode of flexible pavements that generally occurs in the form of irregular (alligator) cracking in the wheel paths. This paper evaluates the effects of applied stress and temperature on the fatigue lives of Polyethylene Terephthalate (PET) modified asphalt mixtures using Response Surface Methodology (RSM). As it is shown in this study a quadratic model is successfully fitted to the experimental data. Fatigue lives of mixtures are influenced by changes in selected… Show more

Fatigue is a major distress mode of flexible pavements that generally occurs in the form of irregular (alligator) cracking in the wheel paths. This paper evaluates the effects of applied stress and temperature on the fatigue lives of Polyethylene Terephthalate (PET) modified asphalt mixtures using Response Surface Methodology (RSM). As it is shown in this study a quadratic model is successfully fitted to the experimental data. Fatigue lives of mixtures are influenced by changes in selected parameters. In addition, the effect of temperature variation is more drastic on the fatigue lives than the effects of stress level and modifier content. Show less

In this paper, the accuracy of soft computing techniques was employed for prediction of the rutting performance of Polyethylene Terephthalate (PET) modified asphalt mixture. The process, which simulates the mixture’s deformation, was constructed with adaptive neuro-fuzzy inference system (ANFIS). The inputs were PET percentages, stress levels and temperatures. The performance of proposed system was confirmed by simulation results. The ANFIS results and the results achieved by experiments were… Show more

In this paper, the accuracy of soft computing techniques was employed for prediction of the rutting performance of Polyethylene Terephthalate (PET) modified asphalt mixture. The process, which simulates the mixture’s deformation, was constructed with adaptive neuro-fuzzy inference system (ANFIS). The inputs were PET percentages, stress levels and temperatures. The performance of proposed system was confirmed by simulation results. The ANFIS results and the results achieved by experiments were compared using root-mean-square error (RMSE) and coefficient of determination. The experimental outcomes suggested that ANFIS approach can be used to improve predictive accuracy and capability of generalization. Show less

Optimization of polymer and asphalt content in polymer modified asphalt mixture is the aim of road engineers and designers. The purpose of this study is to characterize Stone Mastic Asphalt (SMA) mixture’s properties containing waste polyethylene terephthalate (PET) which is a type of polymer material. Response Surface Methodology (RSM) was designated as a new method to measure mixture properties at different PET content and asphalt binder value. To fabricate the mixture fresh 80/100… Show more

Optimization of polymer and asphalt content in polymer modified asphalt mixture is the aim of road engineers and designers. The purpose of this study is to characterize Stone Mastic Asphalt (SMA) mixture’s properties containing waste polyethylene terephthalate (PET) which is a type of polymer material. Response Surface Methodology (RSM) was designated as a new method to measure mixture properties at different PET content and asphalt binder value. To fabricate the mixture fresh 80/100 penetration grade asphalt binder with different percentages (5-7% by weight of aggregate particles) was utilized. Different amounts of PET were used from 0% to 1% by weight of aggregate particles. Marshall Stability and Flow test was performed on the mixtures. Specific gravity and volumetric properties of mixtures were obtained. RSM was used to analyse Marshall and volumetric properties of unmodified and PET modified asphalt mixtures. Models were produced to fit the experimental results. As shown in this study suggested models were successfully fitted to the experimental results. Based on the results achieved amounts of 5.88% of asphalt content and 0.18% of PET were found to be the optimal values. Show less

Predicting asphalt pavement performance is an important matter which can save cost and energy. To ensure an accurate estimation of performance of the mixtures, new soft computing techniques can be used. In this study, in order to estimate the stiffness property of Polyethylene Terephthalate (PET) modified asphalt mixture, different soft computing methods were developed, namely: support vector machine-firefly algorithm (SVM-FFA), genetic programming (GP), artificial neural network (ANN) and… Show more

Predicting asphalt pavement performance is an important matter which can save cost and energy. To ensure an accurate estimation of performance of the mixtures, new soft computing techniques can be used. In this study, in order to estimate the stiffness property of Polyethylene Terephthalate (PET) modified asphalt mixture, different soft computing methods were developed, namely: support vector machine-firefly algorithm (SVM-FFA), genetic programming (GP), artificial neural network (ANN) and support vector machine. Show less

Stiffness of asphalt mixture is a fundamental design parameter of flexible pavement. According to literature, stiffness value is very susceptible to environmental and loading conditions. In this paper, effects of applied stress and temperature on the stiffness modulus of unmodified and Polyethylene Terephthalate (PET) modified asphalt mixtures were evaluated using Response Surface Methodology (RSM). A quadratic model was successfully fitted to the experimental data.

Seventh International Conference on Maintenance and Rehabilitation of Pavements and Technological Control, Auckland , New Zealand

This paper focused on transition safety barrier systems which were located at the point of attachment between a bridge and roadside barriers. The aim of this study was to provide an overview of the behavior of transition systems located at upstream bridge rail with different designs and performance levels. Design factors such as occupant risk and vehicle trajectory for different systems were collected and compared. To achieve this aim a comprehensive database was developed using previous… Show more

This paper focused on transition safety barrier systems which were located at the point of attachment between a bridge and roadside barriers. The aim of this study was to provide an overview of the behavior of transition systems located at upstream bridge rail with different designs and performance levels. Design factors such as occupant risk and vehicle trajectory for different systems were collected and compared. To achieve this aim a comprehensive database was developed using previous studies. Show less

This paper aims to evaluate effects of utilizing waste PET flakes as modifier in asphalt mixture as an alternative solution to overcome the potential risks arise from producing large amount of waste PET as well as evaluating the deformation characteristics of unmodified and PET modified asphalt mixtures. To achieve this aim, different percentages of PET were designated for this investigation, namely: 0%, 0.2%, 0.4%, 0.6%, 0.8% and 1% by weight of aggregate particles, and dynamic creep test was… Show more

This paper aims to evaluate effects of utilizing waste PET flakes as modifier in asphalt mixture as an alternative solution to overcome the potential risks arise from producing large amount of waste PET as well as evaluating the deformation characteristics of unmodified and PET modified asphalt mixtures. To achieve this aim, different percentages of PET were designated for this investigation, namely: 0%, 0.2%, 0.4%, 0.6%, 0.8% and 1% by weight of aggregate particles, and dynamic creep test was performed at different stress levels (300 kPa and 400 kPa) and temperatures (10 °C, 25 °C and 40 °C). Consequently, Zhou three-stage model was developed. Show less

This paper aims to evaluate effects of using waste Polyethylene Terephthalate (PET) as a modifier on properties of asphalt mixture in three steps. In the first step, bulk specific gravity test, Marshall test, indirect tensile stiffness modulus test and indirect tensile strength test were conducted on mixtures containing different percentages of PET. In the second step, permanent deformation of PET modified asphalt mixture were assessed under static and dynamic loads. Finally in the last step… Show more

This paper aims to evaluate effects of using waste Polyethylene Terephthalate (PET) as a modifier on properties of asphalt mixture in three steps. In the first step, bulk specific gravity test, Marshall test, indirect tensile stiffness modulus test and indirect tensile strength test were conducted on mixtures containing different percentages of PET. In the second step, permanent deformation of PET modified asphalt mixture were assessed under static and dynamic loads. Finally in the last step, relationships were found between the results achieved in the first and second steps. Show less

this paper is going to assess deflection and vehicle trajectory of current guardrail systems. For this purpose, the results of full-scale crash tests for different types of guardrail system are collected from previous crash tests available in the literature.

This study aimed to investigate the effects of adding plastic bottles in road pavement. Marshall properties as well as specific gravity of asphalt mixture containing different percentages of plastic bottles were evaluated. Besides, Optimum Asphalt Content (OAC) was calculated for each percentages of plastic bottles used in the mix. The stiffness and fatigue characteristics of mixture were assessed at OAC value.