Journal of Transportation Engineering
Year:2010 | Volume:2 | Issue:1 (5)|Papers Count:7

The purpose of this paper is to simulate train movement and investigate its effect on ground vibration. For this purpose, effective factors on dynamic load magnitude and frequency have been studied and variation of wagon force in a longitudinal model is considered. Fourier Amplitude Spectrum was then computed by means of Fast Fourier Transformation (FFT) of the dynamic train load and the frequency range of train load was determined. In the next step, low energy frequencies were filtered and the dynamic load as a point load was implied on a numerical model of Tehran Subway Tunnel Line 4, as a case study. History of velocity and acceleration in the model surface was then recorded and used as a descriptor to appraise the vibration level. Based on the FTA standard, the induced vibration level leads to residential annoyance in the ground surface. This occurs when two trains with 80 Km/s speed and 100 ton wagon weight pass from the tunnel cross section.

HMA is a mixture of aggregates and liquid bitumen. Aggregates that include both fine and coarse materials, stand for more than %95 of HMA mixtures by weight. The main role of aggregates in the mixture is to convey the traffic load to the layers beneath, therefore the specifications of aggregates significantly affect the mixture properties, specially rutting and stripping. In this experimental project conducted at Iran University of Science and Technology, Bitumen and Asphalt Mixture Center, two sets of specimens were made and defined. The first group of specimens was made with lime aggregate and in the second group, coarse aggregates were replaced by basalt. Comparison was done against rutting, durability, and resilient modulus and Marshal Stability tests. Results show that specimens made with %100 lime material demonstrate better performance compared to specimens containing basalt.

The vital part of every overall maintenance system is "predicting the future condition" sector. This sector will receive all data which are "gathered by inspection systems and saved in data base" and predict the future condition by analyzing this information. In this paper, first of all, the rail condition was categorized according to definition of rail wear defect index and thereafter, the future rail condition on the basis of wear was predicted. In fact, by having two "time and line passing traffic" variables, the future rail condition can be predicted. In addition, the rail life, from the wear point of view, can be estimated by Deterioration Model. Actually, in this research, rail wear in curved track with 250 meters radius was measured with field scan on six-month periods and rail life was predicted by Deterioration Probabilistic Model.

Nearly all the pavements in Iran are made of asphalt concrete. These pavements have short service life due to various reasons. One of the most specific destructions of asphalt pavements is the fatigue crack which occurs due to the numerous traffic loads on the roads. Geotextiles may act as reinforcing agents and increase the service life of asphalt pavements. In this research, three types of geotextiles are studied and their impact on the fatigue life of asphalt beams is investigated. The fatigue test has been implemented by 4 - point bending beam at constant strain condition with haversine wave, 10 Hz frequency. Results show that the fatigue life of all the specimens reinforced by Iranian and other geotextiles is increased, but this increase is higher for the foreign specimens compared to Iranian ones, and at various strain levels for any type of geotextile materials is different. The results also show that the average flexural stiffness of laboratory specimens may be increased or decreased by using geotextiles but totally geotextiles improve the quality of asphalt pavements.

The main objective of this study is to conduct a comparative test program on unmodified and modified bitumen containing nanoclay, and assessing the effects of asphalt properties on performance of the pavement. In order to meet this objective, the main targets of this study are: finding out if the nanoclays alter the critical properties of bituminous binders and influence the ageing and rheology of the bituminous binders. The first task performed was studying the nanoclay modifiers at nanoscopic level and the test performed in this area is x-ray analysis of the nanoclay modifiers. The second task is studying the influence of nanoclay modifiers on bituminous binder characteristics. The tests performed related to this target are rheological studies of fresh (non aged) and aged bitumen types by dynamic shear rheometer (DSR). Findings of the tests performed on bituminous binders proved that the cloisite-15A nanoclay modifications help to increase the stiffness and also improve the rutting resistance of the standard bituminous binder. This is especially true if the %4 cloisite modification is used. The nanofil-15 modification helps to improve the ageing resistance of the bituminous binder in the short and long terms. However, the nanoclay modifications were observed to negatively influence the fatigue resistance performance of asphalt bituminous binders, especially at low temperature values.

Abrasion resistance of water-borne traffic paints caused by traffic flow is one of the most important challenges in urban traffic management. Road marking policy should be made in a manner to assure drivers and pedestrian's safety. In addition, according to the wide ranges of traffic paints application, the paints with adverse environmental impacts should not be used. In this research abrasion resistance of one type of water-borne traffic paint, used in pavement marking in the city of Tehran, has been evaluated. Wet Track Abrasion Test was performed on samples at different conditions. Moreover field works in several streets of Tehran have been evaluated by means of different methods. The evaluation process consists of AS/NZS 4049 and EN 1824. According to laboratory testing results, the water-borne traffic paint used, had good performance in dry conditions. In addition, its performance in simulated winter maintenance conditions (i.e. in presence of sand and salt) was studied. This type of paint showed to have less environmental impacts and exhibited greater retro- reflectivity in comparison with solvent-borne traffic paints. The easy method of application of these types of paint makes them appropriate alternatives for pavement marking operations.

A turnout system in railway signaling based on its function is considered as a safety-critical system. Turnout system consists of point machines, switch rails and interfacing mechanisms. In this paper in addition to introducing the point machine and its functionality, most important faults and their causes and consequences have been described. As the main part of the paper, a general review on different fault detection and diagnosis methods and details of the developing and implementing fuzzy algorithms for fault detection and diagnosis of point machine has been done. The fuzzy rules are developed based on real data from a laboratory based system, installed in the signaling laboratory of the School of Railway Engineering. The algorithm was tested and evaluated for different fault modes of the system. In general, the algorithm is able to detect and locate most of the point machine systems studied in this research work.