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The Effect of Combined Horizontal Curve and Longitudinal Grade on Side Friction Factors
Ali Abdi Kordani,Amirarsalan Mehrara Molan 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.1
The relationship between side friction factor and longitudinal grade is investigated for horizontal curves considered in threedimensions, and new models for estimating side friction factors for different vehicle types are presented. The study consists of threeparts: (1) a series of simulation tests using the CarSim and TruckSim multi-body simulation software packages; (2) multiplexregression analysis; and (3) presentation of recommended formulas for the side friction factor. Two different driving behaviors areconsidered in the simulation process: in one, the driver negotiates the curve at constant speed; in the other, the driver brakes whilepassing downgrades. Side friction factors are also studied separately for each axle of a vehicle. Greater side friction factors are foundon downgrades for all vehicle types when cornering. From the viewpoint of skidding, the most critical situation is found for the rearaxle of a sedan. In addition, braking is found to have a significant effect on side friction factors. The results and models from thisstudy can be used in the geometric design phase by highway engineers to design safer roads.
Abdi Kordani, Ali,Mehrara Molan, Amirarsalan The Korean Society for Railway 2014 International Journal of Railway Vol.7 No.2
Urban subways are one of the main parts of urban transportation networks in every city that always requires much attention in order to improve its efficiency in aspects of safety, reliability speed and costs. As the viewpoint of costs, an accurate design, especially design of vertical alignment, can have a dominant role to reduce the costs of urban railway projects. This paper seeks to evaluate the advantages and disadvantages of designing chain vertical alignment for urban subways in compare to flat vertical alignment. To achieve this goal, line A of Qom subway in Iran was selected as a case study in this research. Five parameters considered in the technical-economical evaluation: (1) energy consumption, (2) rolling stock, (3) operation, (4) civil works and geotechnical and (5) hydrological, drainage and pumping. According to the results, a power saving of about 40% have been estimated in the chain vertical alignment for the train without regenerative braking in compare with the flat vertical alignment, although the power saving was calculated less than 10% for the train with regenerative braking. Finally it was found that due to the modern rolling stock technology, the chain vertical alignment represents fewer advantages in compare to the past years.