فصلنامه مهندسی حمل و نقل
سال پنجم شماره 2 (پیاپی 18، زمستان 1392)

In recent years، transit has been growing at a low rate in Iran; now more than 90 percent of freight transit through Iran territory is transported by road transportation; that is not in line with national transportation policies especially with the national law of fuel management in witch share of rail transportation must be at least 30% of the transit market. This small portion of rail transit is mainly because of low utility of railway corridors. In this study، the parameters affecting the utility of railway transit corridors are investigated، using a system dynamic approach and a utility function for railway transit corridors are presented. Then، using actual data of Sarakhs - Bandar Abbas rail transit route; transit demand in this corridor is simulated up to 2025. Finally، some scenarios are proposed to increasing the utility of the route. The results shows that increase in speed، reducing the train stoppages time and reducing the railway access charge، can significantly increase the route utility and consequently the demand for the route.

The vibrational behavior of embedded rail system is mainly a function of the elasticity of rail embedding resin as well as the geometry of rail seating trough. Reviewing the technical literature in the field of embedded rail slab tracks (ERST) system reveals any study on investigating of the effect of these parameters on the environmental vibration caused by ERST. In the present study by developing a 2D finite element model of embedded rail slab track using ABAQUS software the mentioned issue has been investigated. In this matter and as first stage، the results of the developed model under static loads has been compared with those reported by Esveld et all () and consequently a verified model has been established. In continue، by using the validated model، the vibrational behavior of the model especially the case of environmental vibrations has been studied. In this regard an extensive parametric study has been fulfilled on four key parameters as load amplitude، load frequency، embedding resin elasticity and the dimensions of rail seating trough. The results of these analyses indicated that the varying the elasticity module of embedding resin in the range of 1 to 10 MPa had a great effect on the environmental vibrations. On the other hand it has observed that increasing the trough geometry and consequently its area section leads to reducing environmental vibrations. From another point of view، when the amplitude of the applied harmonic load increases from 1. 5 to 9 tons، the intensity of environmental vibrations increases while by increasing the load frequency، this parameter show decrease. Focusing on loading frequency proved that the maximum and minimum vibrations are corresponding to 5 Hz and 50 Hz and the vibrational effects no so important for frequencies more than 60 Hz.

The study aims at developing a system (DSS) to help policy makers find out the most efficient road safety measures throughout the provinces in Iran. The system serves the purpose to support future road safety decisions based on information on the efficiency of different types of measures taken previously. More specifically، this efficiency، expressed as an index، is calculated based on historical information from previously implemented measures across different regions in Iran. The identified indicators are all linked to road safety measures contributing to the achievement of sustainable road safety. Considering the number of fatalities as the road safety outcome، an efficiency analysis can be carried out for each region to evaluate the efficiency of the measures taken in the past. To do so، inefficiency measure is calculated، defined by the proportion of fatality rates in relation to the combined measure of road safety performance indicators which should be minimized. The relative inefficiency for each region is modeled by the Data Envelopment Analysis (DEA) technique. The inefficiency rate for each DMU must be minimized by either decreased fatality indices and/or increased safety measures to an optimal extent. Using a dual model of the main DEA model for each DMU، a target setting task can be conducted by identifying the benchmarks as the best-performing entities. In a next step، a fuzzy decision making system is constructed to convert the information obtained from the DEA analysis into a rule-based system that can be used by policy makers to evaluate the expected outcomes of certain alternative investment strategies in road safety.

Large increase of vehicles in recent years has led to increase in externalities of transportation in urban streets. Determining of optimal structure of car tax is one of the ways to increase social welfare and to control externalities of transportation. The purpose of this paper is determining optimal car ownership and car use tax in order to minimize car externalities in urban streets. The externality considered in this paper is air pollution including different emissions. Functions used in optimization model are logit discrete choice function and demand function for kilometers. Required data obtained from library sources and various organs like “Tehran Vehicle Technical Inspection Bureau” and “Air Quality Control Company” in Iran. According to obtained results، car ownership and car use tax have been evaluated Based on engine size، vehicle age and fuel. For instance، the average car ownership tax of vehicles with engine size less than 1400 cc and age of less than five years is 6600 Tomans whereas average obtained tax for this group is currently 2000 Tomans. The results show that at first، gasoline cars should pay more car ownership tax and variable cost than hybrid cars with similar age. Secondly، cars with higher age should pay more tax than cars with less age with similar fuel. Also it was found that changing in car ownership tax has low effect on amount of emissions while changing in variable cost influence amount of emissions seriously.

In this article the principle and framework for software design and simulation of traction power supply in urban railway projects are described. The main aim of this design will be creating proper tools and methodology to determine the places of rectifier substations، rectifier unit capacity، choosing of feeder cables and cross dimension n of conductors in traction network and also confirming the capacity of transformers in high voltage posts. Meanwhile an equivalent model for requested network is presented and the equations of network are found. In the model and equations which have large scale and quantities of variables، the optimization numerical method such as Doglag are applied to guarantee the convergence accelerate the speed of solution. The article considers the standards like CEI EN 5032، IEC 146، EN60146 and CEI EN 50329 to ensure the results of obtained model and equations. To verify the credit of presented solution، the line 4 of Tehran metro have been simulated and compared.

Nowadays، the use of ballastless track is developing significantly because of several reasons. Decrease of height، decrease of maintenance cost، increase of service life،speed increasing capability and increase of track lateral resistance can be pointed as some of these reasons. As modern structures require more complex design، the need to assess uncertainities in loads، members geometry، material properties and other factors affecting the performance of the structure is growing. One method of assessing these uncertainties is reliability analysis. There are several methods in reliability analysis to determinate the safety index and the probability of failure. In this project the First Order Reliability Method (FORM) is used to determine the reliability index of a specified slab track. To reach this purpose an structural analysis is done and based on Response Surface Method، the best fitted internal force functions are achieved. Limit state functions are made based on the Eurocode criteria and the reliability index of mentioned slab track is calculated. Also a sensitivity analysis is made in order to determin the result of change of different factors on slab track reliability. Results indicate that the reliability of the studied slab track is adequate and the critical limit state for this slab track is the shear limit state. The yield stress of the reinforcement and concrete strength are the most important factors influencing the reliability of the slab track.

Nowadays various types of materials are used for improvement of grout properties. But selection of suitable grout mix is usually chosen based on the experience of the designer. The aim of this research is using laboratory studies and grout mix choice especially for water-tightening grouting. The procedures flowchart is depicted initially and utilized to choose grout for water-tightening grouting of Karaj water conveyance tunnel. The results obtained from the analysis and investigations of grout mixes have shown in which the purpose of high penetration ability، W/C ratio should be greater than 1. W/C ratio equal to 2 can be named as boundary of “thick” and “thin” grouts. Associated with bleeding and penetration ability، the best grouts will be achieved at W/C ratio in the range of 1 to 1. 5. High percentage of bentonit could be harmful for fresh grout properties. Utilization of Superplastizers in fine cement grouts will be more useful than coarse cement grouts. Also Sodium silicate could reduce setting time of grouts to desired time.

Due to its swelling and losing strength potential، clay is considered to be a problematic soil in highway pavement. However، in many regions، clays constitute the main body of pavement subgrade. One traditional solution for the problem caused by the clays is their stabilization using additives. The main factors affecting on the selection of the type of additive is its effect on the physical and mechanical properties of the soil to achieve the objectives of the stabilization. This paper describes the results of an experimental study، in which the effects of three different stabilizers of lime، cement and CBR PLUS، which is a Nano polymer، on a type of clay soil have been investigated. Different amount of each stabilizers have been added to the soil، and the properties of Atterburg limits، compaction، California Bearing Ratio in dry and saturated conditions، uniaxial compressive strength and permeability of the stabilized soil have been evaluated. The results show that the CBR PLUS is more effective than the other stabilizers on the plasticity index and permeability. Also، it is found that the highest strength is achieved by cement، and the highest ratio of saturated to dry CBR is obtained by lime.

While cold asphalt pavement recycling technologies are well established, there is still a need for additional performance information. Project selection is among the most important factors in assuring the success of a cold in-place recycling project. In this research after investigating the rehabilitation process of Semnan- Damghan highway as a case study, some practical recommendations have been presented which could assist to select a proper project for rehabilitating with recycling technique. In the first stage of field study in addition to the field surveying of pavement condition, both destructive and nondestructive tests have been carried out and the rehabilitation design has been performed with indirect and direct design methods. Based on obtained results Semnan-Damghan highway was divided in to several sections and rehabilitated with conventional and cold recycling rehabilitation techniques. The total length of rehabilitated areas was equal to 165 km which 104 km of them were rehabilitated with recycling technique.After that the pavement performance was monitored during 5 years. Selected techniques were satisfactorily performed in about 154 km of rehabilitated areas. In about 11 km of recycled areas some structural failures were detected after only 6 months from project accomplishment. Precise field surveys revealed that the low compaction and load carrying capacity of subgrade materials and lack of proper base or subbase layers were some reasons of project failure in these areas. Furthermore, there were some shortcomings in the recycled layer specifications which resulted in adverse results. Finally some quantitative criteria were proposed which could be used as practical guidelines in decision of selecting a project to be rehabilitated with cold recycling.