فصلنامه جاده
سال بیست و هشتم شماره 4 (پیاپی 105، زمستان 1399)

According the importance of the transport sector in the economic structure and its crucial role in process of trade and other economic variables, identifying the affecting variables on the activities of these sectors have a high necessity. Therefore, the main purpose of this study is to investigate the effect of exchange rate uncertainty on the value added of the transportation sector from the reducing trade channel. For this purpose, the data for Iran economic in period of 1991-2017 are used and the Bayesian Vector Auto-Regressive (BVAR) model applied to estimates the coefficients. In this study, the Generalized Auto-Regressive Conditional Heteroskedasticity (GARCH) model is used for calculation of uncertainty in the exchange rate. Results indicate on the negative and statistically significant impacts of exchange rate uncertainty on the transport value added. Results also show that GDP and oil revenues have the significant positive impact on the transport value added, but transport price level didn’t have a significant impact.

Soil nailing is one of the common methods used to stabilize excavation walls. This technique has been in attention in recent years. A variety of studies have been performed to optimize the pattern, length and inclination of nails in the design of soil nailing. The nail inclination has been one of significant optimization variables considered in previous studies. As a constraint of the optimization process, it has been assumed in previous studies that the inclinations of all nails through the depth of a soil-nailed wall must be equal. On the contrary, the present study presumes that the inclination of each row of nails could be different; in other words, the inclination of each row of nails is an independent optimization variable. The present study takes into account two approaches to optimize the design of soil nailing. In the first approach, the ratio of the maximum length of nails to the wall height is unconstrained but in the second approach, it is limited to the ratio proposed by the FHWA manual. The results of the present study show that two optimization approaches lead to different optimized inclinations for nails. For the first approach, the optimized inclination of all rows of nails equal to be 5 degree with respect to the horizon but in the second approach, these inclinations are different for rows of nails in the way that they reduce from the top row to the bottom one.

Train timetabling is one of the most important problems in railways systems. The framework of this problem is the same in different countries but in some countries, there is a special rule which makes special conditions on the modeling of this problem. In Iranian railways, praying causes an obligatory constraint because Muslims people have to pray 5 times a day. In this paper, we present a train timetabling model which allocates the best station where Muslims can pray. The goal of this model is to minimize the total train trips by considering allowed duration between trains stops and the time each Muslim could start his or her praying. The approach of the Iranian railways is to minimize this duration because it is important for Muslim to start their praying just on time. The model has implemented on one of the Iranian double tracks railways and the results show the total train trips increases by decreasing the duration.

Today, the growing trend of accidents in roads and casualties are the result of loss of national capital. These factors and the expression of practical solutions can reduce the incidence of such incidents. Behavioral abnormalities in driving are considered as a serious problem in society. Lack of skills in vehicle control, fatigue, drowsiness and exceeding speed limits, road geometry and psychological and economic problems are the causes of accidents in the country. Investigating the causes of traffic accidents shows that in addition to learning and acquiring skills and experience in the control of vehicles psychological factors, stress and economic situation also have a special role in preventing accidents. In this study, the effect of psychological behavior of heavy vehicle drivers on Zanjan-Tabriz axis crash rate is investigated. The statistical population of this research is heavy vehicle drivers and the study area is Zanjan-Tabriz axis in 1397 which was done by questionnaire method using SPSS20 software. The results showed that the exhaustion parameters of fatigue and drowsiness, economic factors, road geometry and stress had a positive and significant effect on the rate of accidents.

Today, urban transport and traffic has always been a major topic in urban studies, and is one of the most important needs of urban life, the main pillars of what is called sustainable development is the creation of a sustainable transport system. Transportation in cities has become one of the major challenges for governments in the political arena. Appropriate transportation systems are one of the hallmarks of countries 'and communities' development. The main objective of the present study is to determine the most important factors and indicators affecting urban transportation using the experience of urban transport. Leading cities are in the process of transportation. The study is applied-developmental in terms of content-analytic method. Quantitative and qualitative techniques were analyzed using SPSS and GIS software. Library and field methods in relation to sustainable transport indicators are. Communication and Network Access The city has problems and limitations and I need access network the reform is.

This study investigates the possible uses of fiber bundles, shredded tire and tire cord scrap (individually and in combination with cement) in clayey sand stabilization. Several basic characteristics of experimental specimens obtained with Atterberg limit, standard proctor compaction, and unconfined compression strength (UCS). These properties are compared with those of un-stabilized clayey sand and stabilized clayey sand with cement and the observed test results are then explained. Results of experimental study indicate that cement mixture treatments play a prominent role in reducing the soil plasticity index (PI). Furthermore, the results of the compaction test show that the utilization of waste in sandy soil stabilization decreases the optimum moisture content and also decreases the maximum dry density. Among the used waste materials, fiber bundles showed the greatest impact on maximum dry density with 1.4% reduction. The results show that using waste materials alone to stabilize clayey soil results in a slight increase in the UCS of the specimens, whereas combining waste with cement results in a sharp increase in the UCS of the samples in the same curing time. Additionally, the samples treated with fiber bundles have the most remarkable increase in UCS and maximum displacement compared to other samples, respectively 32 and 58 percent. The reason that fiber bundles becomes more efficient waste material is rooted from rising the contact area, plummeting the specific gravity and augmenting the uniform distribution in the clayey sandy soils.

The effects of earthquakes on the road beds and the structures on it (the site in general) can be very variable, so that in some areas the acceleration of the earthquake at the ground level is amplified or, conversely. This issue can be related to several factors. In the present study, the Earth's response has been investigated by looking at the characteristics of the Kermanshah regional bed due to the application of force caused by the Upland earthquake with the help of two-dimensional finite element software (PLAXIS) .Two-dimensional numerical analyzes were performed for dry soil, drained saturated soil and undrained saturated soil. Results show that the presence of pore water (in undrained conditions) can increase the acceleration on the earth's surface up to 3 times compared to the dry state mode. However, at the same time, the overall displacement rates in all three modes of dry bed, drained saturated, and undrained saturated condition are not much different. Another noteworthy point about Kermanshah's site is that the closer to the soil surface (the location of the structure), the ground response more and more grows, and finally reaches its maximum in surface level.

Stability studies on rocky slopes, which are an example of geotechnical structures, is regarded as one of the most decisive engineering fields for designers. The significance of this field is immense to the extent that any malfunction of these structures may generate irreparable damages. Unpredictability and variability of physical and mechanical properties of soils and rocks, as well as errors made in measurements, has brought forth the application of reliability-based analyzes in geotechnical engineering into further consideration. Accordingly, stone gables are modeled, and their respective rock slope stability under the force of the dynamic load is examined in this study. Moreover, if the slopes are determined to be unstable, an adequate and optimal method will be devised and proposed by means of using a net to ensure their stability. A stone gable with slope angles of 10, 20, and 30 degrees was subject to analysis, and the gable's stability was evaluated with the aid of manual methods. Subsequently, the stone gable's finite element model, in a two-dimensional state, is constructed via phase.2 software, and the rock slope stability assessment is conducted under static and dynamic conditions. Following, the stability of the stone gable is similarly examined and assessed by placing the net with the rock bolts. Remarkably, the arrangement analysis of bolts is also performed in the course of the rock slope stability evaluation of the stone gables under the force of dynamic and static loads.

Due to the growing technology of various types of vehicles and their increasing application in the transportation network, the development of road quantity and quality is of particular importance. One way to improve and increase the strength of pavements is to use high-quality materials such as steel slag, which will increase the bearing capacity of the pavements and their life span. Steel slags are by-products of the steel factory, which are often stored as deposits and massive masses around these factories. Over the years, extensive research has been conducted around the world for the use of this substance and several fields have been proposed for this purpose. One of these fields which use the steel slags in large amounts, is as the aggregate in the production of asphalt. This is because it has good physical and frictional properties as well as good durability in resisting the slippage of asphalt pavement and preventing the formation of some deterioration, such as rutting, stripping and polishing of asphalt aggregates. In the present study, in addition to studying the mechanical, physical and chemical properties of steel slag as an aggregate alternative in asphalt pavements, the most recent studies have been mentioned and the use of steel slag in road construction including base and sub-base, and asphalt mixes have been investigated.