Journal of Transportation Engineering
Year:2009 | Volume:1 | Issue:1|Papers Count:7

Steel wheels are affected during coach operation on the rail due to high normal and tangential stresses. The wheel profile is then varied, which could be resulted in an unexpected derailment when wheel wear is focused on within the flange region. This dangerous situation should be prevented, using various solutions including the deployment of higher grades of steel wheels. A field test was planned and conducted within 2007-2008 period to find out the influence of B5T grade steel on the wheel wear magnitude and pattern, which could lead to safe operation of a passenger coach. The test coach wheels were measured frequently at Tehran station for a 5-month time interval. It was found that B5T grade has a better strength to resist against wheel failure mechanisms, i.e., wear as well as rolling contact fatigue (ref) in comparison with B2N grade which was tested during 2003-2004 period in the same route, that was Tehran-Mianeh track. The wear pattern was gained more symmetric within each wheel set (about 25%) than the previously used wheelsets within field test results. Consequently, this coach likely operated longer life (40%), as well as, safer than the earlier test coach which had been equipped with B2N grade steel wheels. To justify the higher wear rate at the initiation of coach operation, it could be explained when the running-in period of wheels was finished, a harder material raised to the wheel surface resulted in a balanced material removal condition in terms of wear. As a result, the wear rate of the wheels was gradually decreased.

Due to the safety of Rail transportation, Investigation on characteristics and phenomenon which causes accidents has an important role, in order to enhance the safety of rail transport and, in turn, reduce the rate of accidents. According to the rail accident statistics, among all factors causing train accidents, derailment has the biggest share, which can be because of human errors, track and rolling stock deficiencies, etc. Investigation and technical analyses of these factors will be complicated, because of the quantitative/qualitative relationships. Investigation on available derailment results indicates that a few numbers of traditional analytical models have been used. Herein, limited capability of these models such as being one dimensional, taking not into account all factors involved and complexity in behavior description can be clearly observed. Regarding the importance of the current situation in the derailment investigation, in this research a new combined intelligent Neuro-Fuzzy model has been developed. This study has simplified the quantitative/qualitative behavior description for derailment, prepared and simplified a practical and more accurate quantitative/ qualitative evaluation to achieve multi-dimensional decision making evaluation model, by using Adaptive Neuro Fuzzy Inference System (ANFIS). This research has developed a method of operation based on human factors. Regarding the results, analyses of the developed N-F model make a foundation for a more comprehensive accident management system.

One of the main issues in track maintenance-management systems which is required for organizing rail line's repair and maintenance activities, is evaluation of superstructure conditions. Slab tracks superstructure condition in respect of maintenance parameters is a qualitative issue which should be converted to a quantitative parameter in order to maintenance operation decision making and forecasting of rail road future condition in a management system. In this case the track structure condition index and track geometry condition index are used. However, a comprehensive method for evaluation of slab track superstructures isn't presented yet, in spite of significant development of slab track systems in Iran and all around the world. The methodology which is given in this research, is used in development of evaluation models based on mechanical and field inspection. Field researches and inspections of some parts of main slab tracked rail road were done, in order to calibrating the model and its experimental implementation on a test route. track structure condition indexes in our case study track was 95,89 and 88 for fastener, slab track and ordinary rail group respectively, which shows that converting slab track's components quality condition to quantity based on offered methodology and what we expected for, has appropriate result. It shows also that damages categorizing and its intensity limitation in order to determining different kinds of damages is suitable. The track geometrical condition indexes which are used in this research, consider mean parameter in addition to standard deviation. Geometrical index for case study is between 0 and 3.02 in slab track which satisfies sufficient requirements to let the train pass safely.

Bridges are unique in their structural response compared to buildings. As the bridges are considered as vital lifelines in transportation, providing sufficient seismic security is very important. However, bridges have a lower degree of static indeterminacy than buildings; Hence, failure of a part of structural element such as a column or a foundation likely results in a collapse of the entire bridge system. During an earthquake, a RC column can fail in three main modes due to cyclic axial and lateral loads: shear failure, flexural plastic hinge failure, and lap splice failure. In recent years, Use of FRP composites as one of the strengthening techniques for reinforced concrete bridges, has been increasingly developed. The Fiber Reinforced Polymer (FRP) strengthening procedure would cause minimal increase in size and weight of structural members, ease of installation and efficient corrosion resistance. In this paper a compressive strength model for confined concrete wrapped with fiber- reinforced polymer has been proposed which is an extension of Mohr's strength theory. This model relates the confined compressive stress to the confining pressure. In the general form this model requires information about the uni-axial compressive strength, the uni-axial tensile strength and a quantity, n, relating to the shape of envelope of ultimate strength states. A second-order parabolic model, developed analytically, is proposed for using with FRP-confined concrete. The proposed model has been verified using existing tests of normal strength concrete specimens confined by FRP wrap. An application example for strengthening a reinforced concrete bridge column is also provided.

According to the growing trend of aircraft industry, a variety of different airplanes exist in this market which vary in type of use, figure (geometry) and gear configuration. In this article, we use the latest Federal Aviation Administration software for a numeral study and research about effect of Airbus and Boeing gear configuration on airfield's runway rigid and flexible pavements. Cumulative damage factor (CDF) is the amount of the structural fatigue life of a pavement which has been used up, and this research calculates this amount for Airbus and Boeing airplanes. This research shows that B-777 among Boeing aircrafts, and A-340 among Airbus aircrafts, have the most damage on flexible and rigid pavements. Furthermor, the Cumulative Damage Factor contribution on rigid and flexible pavements are compared for both Boeing and Airbus aircrafts.

The ground motion of near-field earthquakes is characterized by a high peak acceleration and a velocity pulse with a long period component as well as a large displacement. In this article, the application of the concept of active control for the reduction of the destruction caused by near-field earthquakes in brigde benchmark structures is investigated. In this vein, artificial neural network and fuzzy logic and combination of artificial neural network and fuzzy logic for the design of active algorithm are used. The most significant advantages of fuzzy controller are inherent stability and capacity for the survey of the non - linear behavior of the structures. The fuzzy logic used in this article uses directly crisp data derived from sensors. This data is converted to fuzzy language or the membership functions during the fuzzification process. In addition to the fuzzy logic procedure in the present article, a back-propagation algorithm based on artificial neural networks is also used. A step-by-step non-linear analysis is done using new-mark-B, and for better representation of the non-linear behavior, a bilinear hysteresis model is used to model plastic hinge. In this article, for the evaluation of the designed control algorithm efficiency, some near-field records are used. These records consist of seventeen (17) evaluation criteria and are compared using LQG style. The evaluation criteria used are divided to four categories1) Structural responses2) Structural damage3) Control devices4) Control strategic requirementsThe comparison of the results obtained in case of evaluation criteria of active control algorithm designed in this article and LQG style, firstly was the transformation shown in the appropriate algorithm for near- field and far-field earthquakes and secondly it is assumed that the active control algorithm designed with the fuzzy logic is the most appropriate algorithm for the reduction of the destruction caused by near- field earthquakes

Although the current analysis and design of railway track systems are based on the assumption of continuous and linear behavior of the rail support system, repair and maintenance plans have considerable influences on the structural behavior of the track support system, particularly after accumulative loading or track tamping. Recent experimental investigation indicated the behavior of the track support system is time and stress dependent. The amount of traffic passed and the quality and quantity of maintenance activities can considerably influence the track response functions. Although some experimental investigations have been carried out to study the time and stress dependent characteristics of the ballast and subgrade materials, the effects of the consideration of these characteristics on the track analysis and design, need further evaluations. Furthermore, the recent extensive increases in axle loads, speed and traffic volumes in rail transport systems, require more precise analytical and mechanistic approaches for railway track system. This research is a response to this need. In this paper, the current practices in the analysis and design of railway track system are discussed. A mode of track support system with consideration of discrete supports is developed. By comparison of the analyses results obtained from track models with continuous and discrete support systems, the accuracy of the assumption made in the Winkler model, used in the current design approach, are evaluated. The nonlinear behaviors of the track support system were studied and the influences made by the consideration of the non-linearity of the track support system on the rail design criteria were investigated. Rail bending moments and rail deflections as the main rail design criteria are obtained form track with a linear support and nonlinear behaviors. Obtaining large discrepancies between the results obtained from linear and non-linear analyses, the importance of the track regular and systematic repairs, in particular tamping and stabilizing the ballast, are proved. It is shown that the consideration of regular repairs of the track support system improves the long term reliability and accuracy of the current track design approach. Recommendations are made on the track maintenance and repairs in order to keep the track support system in the linear conditions.