فهرست مطالب

Transportation Engineering - Volume:3 Issue: 3, Winter 2016

International Journal of Transportation Engineering
Volume:3 Issue: 3, Winter 2016

  • تاریخ انتشار: 1395/03/30
  • تعداد عناوین: 6
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  • Vahid Ayan*, Alireza Khavandi, J. R. Omer, M.C. Limbachiya Pages 171-180
    The policy of driving organization such as Highways Agency is towards the use of performance related specifications. This policy and adoption of European wide aggregate standards on the one hand, and sustainable construction pressures on the other, all strongly emphasize on further need for more developments to specifications and performance assessment methodologies instead of creating barriers to the use of suitable materials. Performance related specifications for pavement foundations are being developed and are primarily based around in-situ control and compliance testing. Laboratory based tools for assessment of the performance of foundation materials and their durability under adverse conditions would be a key factor to the successful use of alternative materials. The toughness performance of recycled concrete aggregates (RCA) mixed with natural aggregates (NA) was evaluated based on the test specifications given in the NCHRP Report 598. For this purpose Los Angeles Abrasion and degradation test results were correlated with established Micro Deval designations in NCHRP report 598.Three main factors involved in performance assessment; i.e. (a) traffic loading, (b) moisture levels in highway pavements and (c) the temperature conditions. The research study showed that the materials were appropriate for unbound subbase for medium traffic in non freezing condition from the standpoint of toughness. Also they are suitable for low traffic situations with low moisture and freezing weather.
    Keywords: Recycled aggregate, toughness, Performance, pavement
  • Zahra Elahi*, Meisam Akbarzadeh Pages 181-188
    In design and analysis, standard references assume the pedestrian flow as unidirectional. In reality however, pedestrian flow is usually bi-directional. The main question pursued in this paper is that whether the main characteristics of pedestrian flow the same under uni- and bi-directional conditions. In order to achieve this goal, effect of bi-directional stream is investigated on behavior and main parameters of pedestrian flow. Part of the data for the research was collected via controlled experiments and another part was videotaped from Isfahan walkways. It is shown that under bi-directional condition, mean speed of pedestrians is significantly more than the similar condition under uni-directional regime. Moreover, relative discrepancy between pedestrian speeds in two types of flow becomes evident in densities higher than 0.6 person/m2. Speed of pedestrians in the majority and minority group were recorded and there from it was concluded that the density in the vicinity of a person has a greater effect on her walking speed compared to the opposite flow. In order to avoid colliding to opposite flow, pedestrians try to follow the preceding person and therefor lines are established within the crowd. Fundamental diagrams are also derived for different directional ration. As the index of disorder, entropy was calculated for uni- and bidirectional flows. It was concluded that entropy was lower for bidirectional flows which means that order improves under bidirectional regime of flow. This is in accordance with less freedom of movement under bidirectional regime.
    Keywords: Fundamental diagram, pedestrian flow, bidirectional flow, traversing lines, entropy
  • Iman Salehi Hikouei, Abolfazl Hasani*, Ziba Shirkhani Kelagari Pages 189-194
    The Stiffness modulus is one of the necessary inputs in mechanistic-empirical pavement design and Quality Assurance/Quality Control (Q Q A C ) of pavement layers construction. The use of Portable Falling Weight Deflectometer (PFWD) for measuring the stiffness modulus of unbound pavement layers is increasing worldwide. The modulus can also be indirectly calculated by the results of other available devices. The Dynamic Cone Penetrometer (DCP) is an easy-to-access device for evaluating the strength of unbound pavement layers in a cheap, easy and fast way. In this study, the stiffness modulus of PFWD and penetration rate of DCP was correlated for the sub-grades ranging from well-graded sand (SW), which is highly consisted of SiO2 and Al2O3, and well-graded gravel (GW) classification. In addition, the results indicated that a good correlation exists between PFWD moduli and DCP results and also for the precise evaluation of the SW soil modulus with a considerable amount of SiO2 and Al O3, a coefficient factor, of C = 2.39 , was presented.
    Keywords: Stiffness Modulus, PFWD, DCP, mechanistic, empirical
  • Ali Siyahi, Amir Kavussi*, Amin Mirza Boroujerdian Pages 195-206
    Low skid resistance of road marking paint is one of the major issues in the safety of vehicle drivers, cyclists, and pedestrians when traveling on the city streets. Among the variety of marking paint, two-component paint is widely used at intersections and roundabouts. Therefore, the paint used should have adequate skid resistance. The object of this study was to evaluate the skid resistance and other physical properties of twocomponent road marking paint that is widely used in Tehran. Several additives were used and with the use of a British Pendulum Skid Resistance Tester, the skid resistance values (SRV) of the specimens were determined. In addition, abrasion resistance, reflectivity and adhesive properties of the specimens were evaluated. The tests results showed that the conventional road marking paint has a poor skid resistance. The problem may be resolved by using additive materials such as waste glass powder, silica granules and Lika (i.e. expanded clay). Results suggest that waste glass powder has shown a better performance than the other additives, as it enhances the skid resistance of the paint. According to the pendulum test values, the application of waste glass powder as much as 10% by weight of road marking paint may respectively increase the skid resistance and reflectivity up to 21 units (from 38 to 59) and 40 units (from 239 to 279) so that it does not impose much negative impact on the other properties of the paint. It was that the additive materials caused a reduction in the abrasion resistance of the road marking paint.
    Keywords: Two, component road marking paint, skid resistance, abrasion resistance, reflectivity, adhesive strength
  • Reza Tavakkoli, Moghaddam*, Zohre Razie, Siavash Tabrizian Pages 207-225
    This paper presents a novel bi-objective multi-product capacitated vehicle routing problem with uncertainty in demand of retailers and volume of products (UCVRP) and heterogeneous vehicle fleets. The first of two conflict fuzzy objective functions is to minimize the cost of the used vehicles, fuel consumption for full loaded vehicles and shortage of products. The second objective is to minimize the shortage of products for all retailers. In order to get closer to a real-world situation, the uncertainty in the demand of retailers is applied using fuzzy numbers. Additionally, the volume of products is applied using robust parameters, because the possible value of this parameter is not distinct and belongs to a bounded uncertainty set. The fuzzy-robust counterpart model may be larger than the deterministic form or the uncertain model with one approach and it has with further complexity; however, it provides a better efficient solution for this problem. The proposed fuzzy approach is used to solve the bi-objective mixed-integer linear problem to find the most preferred solution. Moreover, it is impossible to improve one of the objective functions without considering deterioration in the other objective functions. In order to show the conflict between two objective functions in an excellent fashion, a Pareto-optimal solution with the ε-constraint method is obtain Some numerical test problems are used to demonstrate the efficiency and validity of the presented model.
    Keywords: Capacitated vehicle routing problem, bi, objective model, Robust optimization, fuzzy optimization, multiple products
  • Hassan Ziari, Ali Moniri*, Mohammad Javad Ayazi, Mostafa Nakhaei Pages 227-235
    Copper slag (CS) is an abrasive blasting grit made of granulated slag from metal smelting processes. As copper slags are known to be waste material and cause a lot of environmental problems, it would be a good idea to use them in different sections of industry such as pavement construction. On the other hand, in order to save energy and reduce the amount of pollutants released during the construction of asphalt pavements, the technology of Warm Mix Asphalt (WMA) is developing considerably. A very high amount of copper slag is produced in south of Iran where the weather is considered to be hot and rutting is the most important distress of asphalt concretes. This paper presents the influence of utilization of copper slag as fine material on the rutting performance of warm mixed asphalt. A laboratory study has been conducted on five asphalt mixtures with various CS contents, namely; 0%, 10%, 20%, 30% and 40% by weight of total aggregates. The amount of optimum bitumen and the value of Marshall Stability (MS) were determined with MS test for the samples. Then creep test and wheel track tests were conducted on the produced samples. The results indicated that the use of 20% CS in WMA enhances the marshal stability and rutting performance of WMA mixtures. However, the resistance of mixtures against rutting falls substantially by adding more than 20% CS.
    Keywords: Copper slag, warm mix asphalt, by, products in asphalt mixtures, Moisture Sensitivity, creep test