فصلنامه مهندسی حمل و نقل
سال سوم شماره 1 (پیاپی 9، پاییز 1390)

In recent years, railway transportation has had considerable advancements, relying on increasing axle load and speed of trains. If the ground noise and vibration from railway transit systems are not controlled, they would have significant effects on residential areas and other sensitive locations. The technical review of existing literature on reducing vibrations due to train passing on nearby buildings indicates that various methods of vibration control including reduction of vibration in wave propagation path and receiver building have been presented by several researchers. Excavation of trenches in two sides of railroads is one of the best methods to attenuating vibrations due to train passing. As the shape effect of open trenches to reduce the vibrations has not been studied, therefore in the present study, the V-shaped trench has been investigated in comparison to common rectangular shaped trench for attenuating vibrations. For this reason, vibration effects of MD36 bogie with different speeds has been studied with finite/infinite element method implemented in ABAQUS software. Results show that the V-shaped trench has more satisfactory performance compared to rectangular shaped trench with the same area. Maximum amplitude reduction ratio for displacement of surface ground before V-shaped trench shows a less value regarding to common rectangular shaped one for train speeds of 80 and 120 Km/hr.

Rail lines consist of a big fleet of different kinds of locomotives. Allocating the locomotives to the trains is one of the operational purposes in railways. Considering the network development and some out of service locomotives, the improved operation of locomotives is of special importance. Regarding the traditional allocation, there is no appropriate utilization of the locomotives presently, which is one of the reasons for the inappropriate allocation of locomotives to the trains. In recent studies, the items like different traction powers of each locomotive, the possibility for combination of different kinds of locos and utilization of passenger and freight locomotives have not been considered. Therefore in this research, a new mathematical model for locomotives allocation to trains has been presented, which is more compatible with RAI’s structure. The presented model is solved using GAMS software by solver Cplex 7.0 and shows that by improved allocation of the locomotives to the trains, in the existing conditions, nearly %20 can be saved by operation of locomotives.

In order to investigate the effectiveness of traffic mitigation strategies and economic analysis of transportation projects, the dynamic modeling of transportation network is necessary. In this regard, it is important to model the dynamic process of drivers’ route choice. Many models have been proposed for the modeling of drivers’ route choice over the past decades; however only a few of them are dynamic, and most of them are static based on economic theories. In this paper, a dynamic (day-to-day) route choice model is presented. The proposed model is implemented on a small test network, and the process of drivers’ route choice in several scenarios is discussed afterwards. Result may reflect the fact that the proposed approach can be considered as a promising method in the realm of day-to-day route choice modeling.

The prediction of pavement responses on the basis of Advanced Finite Element Programs provides endless opportunities for the analysis of complex problems in the pavement engineering. Reducing considerable time in the analysis of such problems with the model of artificial neural network analysis is possible. Artificial neural networks are functionally very practical models whose calculational speed is entirely independent of the complexity of mathematical algorithms or the method used for providing training samples. In this paper, the analytical results of 624 jointed plain concrete specimens is used in order to choose an appropriate neural network algorithm as a reliable tool for road rigid-pavements response. The suggested analytical model is based on results of artificial neural network in the form of a 6-18-2 back propagation ANN network with sigmoid transfer function which provides ability to find critical stress and deflection in PCC in short time for generating model and analysis process of several pavement sections simultaneously.

Systematic reduction of accidents needs a comprehensive road safety management. The determination of black spots referred to as hazardous road location (HRL) is the first step for the highway safety management process. Identification of the HRLs needs to quantification of the hazard measures. Employing simple measures such as frequency, rate and cost of accidents may cause many errors because of random changes in accident, annually. Another method to identify HRLs is use of regression models applied for computing of accident frequency and their severities in different temporal and special patterns. The requisite of regression models is a statistic function calibrated by explanatory and dependent variables, also special assumptions have to be considered for data distribution and model limitation. The aim of the present study is representation of a novel method to pronounce accidents with regard to traffic, geometric and environmental circumstances of road which can consider the interaction of accidents as well as their casual factors. This approach segments the road to homogeneous sections; therefore, decisions about road safety condition would be made for a length of road with the specified parameters instead of a spot which is called accident prone section (APS). This method has been done with data envelopment analysis technique. Proper rating can be possible by obtaining inefficiency values from this method for road sections. A case study has been done in 144.4 km which resulted in identifying 154 sections with different relative hazard scores. Accordingly APSs have been identified and prioritized with the proposed method which is a new experience based upon the definitions of inputs and outputs according to data envelopment analysis.

Due to the critical situation of environmental issues, waste materials recycling and their reusing has been a research interest for many researchers. Recycled Asphalt Pavement (RAP) is a waste material which may have unfavorable influence on its surrounding environment. Considering the reported characteristics of these materials, different strategies to reuse RAP’s have been introduced. One of these applications recently noticed by the researchers is using RAP’s in cement mixtures such as concrete. As RAP is mainly collected from roadsides and highways, so it is desirable to use it in common mixtures for roads pavements. Hence, Roller Compacted Concrete - a concrete mixture with unique featues such as ease of application and low cost- was selected as the basic mixture. In this research, replacing a part of aggregates with RAPs in three states was carried out: 1- with fine and coarse aggregates, 2- with just fine aggregates, and 3- with just coarse aggregates, with ratios of 0, 10, 20, 40, and 80 percentages. Tests results indicated that use of RAPs as a part of aggregates in pavement Roller Compacted Concrete has no effect on the consistency of concrete compressibility, and cement and water batches; however, the compressive strength is reduced by increased quantity of RAP aggregates.