فصلنامه مهندسی حمل و نقل
پیاپی 1 (پاییز 1388)

Steel wheels are affected during coach operation on the rail due to high normal andtangential stresses. The wheel profile is then varied, which could be resulted in anunexpected derailment when wheel wear is focused on within the flange region. Thisdangerous situation should be prevented, using various solutions including thedeployment of higher grades of steel wheels.A field test was planned and conducted within 2007-2008 period to find out theinfluence of B5T grade steel on the wheel wear magnitude and pattern, which couldlead to safe operation of a passenger coach.The test coach wheels were measured frequently at Tehran station for a 5-month timeinterval. It was found that B5T grade has a better strength to resist against wheelfailure mechanisms, i.e., wear as well as rolling contact fatigue (rcf) in comparisonwith B2N grade which was tested during 2003-2004 period in the same route, thatwas Tehran-Mianeh track. The wear pattern was gained more symmetric within eachwheelset (about 25%) than the previously used wheelsets within field test results.Consequently, this coach likely operated longer life (40%), as well as, safer than theearlier 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 beexplained when the running-in period of wheels was finished, a harder materialraised to the wheel surface resulted in a balanced material removal condition in termsof wear. As a result, the wear rate of the wheels was gradually decreased.

Due to the safety of Rail transportation, Investigation on characteristics andphenomenon which causes accidents has an important role, in order to enhance thesafety 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 androlling stock deficiencies, etc.Investigation and technical analyses of these factors will be complicated, because ofthe quantitative/qualitative relationships.Investigation on available derailment results indicates that a few numbers oftraditional analytical models have been used. Herein, limited capability of thesemodels such as being one dimensional, taking not into account all factors involvedand complexity in behavior description can be clearly observed. Regarding theimportance of the current situation in the derailment investigation, in this research anew combined intelligent Neuro-Fuzzy model has been developed.This study has simplified the quantitative/qualitative behavior description forderailment, prepared and simplified a practical and more accurate quantitative/qualitative evaluation to achieve multi-dimensional decision making evaluationmodel, by using Adaptive Neuro Fuzzy Inference System (ANFIS). This research hasdeveloped a method of operation based on human factors. Regarding the results,analyses of the developed N-F model make a foundation for a more comprehensiveaccident management system.

One of the main issues in track maintenance-management systems which is requiredfor organizing rail line’s repair and maintenance activities, is evaluation ofsuperstructure conditions. Slab tracks superstructure condition in respect ofmaintenance parameters is a qualitative issue which should be converted to aquantitative parameter in order to maintenance operation decision making andforecasting of rail road future condition in a management system. In this case thetrack structure condition index and track geometry condition index are used.However, a comprehensive method for evaluation of slab track superstructures isn’tpresented yet, in spite of significant development of slab track systems in Iran and allaround the world. The methodology which is given in this research, is used indevelopment of evaluation models based on mechanical and field inspection. Fieldresearches and inspections of some parts of main slab tracked rail road were done, inorder 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 forfastener, slab track and ordinary rail group respectively, which shows that convertingslab track’s components quality condition to quantity based on offered methodologyand what we expected for, has appropriate result. It shows also that damagescategorizing and its intensity limitation in order to determining different kinds ofdamages is suitable. The track geometrical condition indexes which are used in thisresearch, consider mean parameter in addition to standard deviation. Geometricalindex for case study is between 0 and 3.02 in slab track which satisfies sufficientrequirements to let the train pass safely.

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

According to the growing trend of aircraft industry,a variety of different airplanesexist 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 anumeral study and research about effect of Airbus and Boeing gear configuration onairfield's runway rigid and flexible pavements. Cumulative damage factor (CDF) isthe amount of the structural fatigue life of a pavement which has been used up, andthis research calculates this amount for Airbus and Boeing airplanes. This researchshows that B-777 among Boeing aircrafts, and A-340 among Airbus aircrafts, havethe most damage on flexible and rigid pavements. Furthermor, the CumulativeDamage Factor contribution on rigid and flexible pavements are compared for bothBoeing and Airbus aircrafts.

The ground motion of near-field earthquakes is characterized by a high peakacceleration and a velocity pulse with a long period component as well as a largedisplacement. In this article, the application of the concept of active control for thereduction of the destruction caused by near-field earthquakes in brigde benchmarkstructures is investigated. In this vein, artificial neural network and fuzzy logic andcombination of artificial neural network and fuzzy logic for the design of activealgorithm are used.The most significant advantages of fuzzy controller are inherentstability 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. Thisdata is converted to fuzzy language or the membership functions during thefuzzification process. In addition to the fuzzy logic procedure in the present article, aback-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 betterrepresentation of the non-linear behavior, a bilinear hysteresis model is used tomodel plastic hinge. In this article, for the evaluation of the designed controlalgorithm efficiency, some near-field records are used. These records consist ofseventeen (17) evaluation criteria and are compared using LQG style. The evaluationcriteria used are divided to four categories:1) Structural responses2) Structural damage3) Control devices4) Control strategic requirementsThe comparison of the results obtained in case of evaluation criteria of active controlalgorithm designed in this article and LQG style, firstly was the transformationshown in the appropriate algorithm for near- field and far-field earthquakes andsecondly it is assumed that the active control algorithm designed with the fuzzy logicis the most appropriate algorithm for the reduction of the destruction caused by nearfieldearthquakes.

Although the current analysis and design of railway track systems are based on theassumption of continuous and linear behavior of the rail support system, repair andmaintenance plans have considerable influences on the structural behavior of thetrack support system, particularly after accumulative loading or track tamping.Recent experimental investigation indicated the behavior of the track support systemis time and stress dependent. The amount of traffic passed and the quality andquantity of maintenance activities can considerably influence the track responsefunctions. Although some experimental investigations have been carried out to studythe time and stress dependent characteristics of the ballast and subgrade materials,the effects of the consideration of these characteristics on the track analysis anddesign, need further evaluations. Furthermore, the recent extensive increases in axleloads, speed and traffic volumes in rail transport systems, require more preciseanalytical and mechanistic approaches for railway track system. This research is aresponse to this need. In this paper, the current practices in the analysis and design ofrailway track system are discussed. A mode of track support system withconsideration of discrete supports is developed. By comparison of the analysesresults obtained from track models with continuous and discrete support systems, theaccuracy of the assumption made in the Winkler model, used in the current designapproach, are evaluated. The nonlinear behaviors of the track support system werestudied and the influences made by the consideration of the non-linearity of the tracksupport system on the rail design criteria were investigated. Rail bending momentsand rail deflections as the main rail design criteria are obtained form track with alinear support and nonlinear behaviors. Obtaining large discrepancies between theresults obtained from linear and non-linear analyses, the importance of the trackregular and systematic repairs, in particular tamping and stabilizing the ballast, areproved. It is shown that the consideration of regular repairs of the track supportsystem improves the long term reliability and accuracy of the current track designapproach. Recommendations are made on the track maintenance and repairs in orderto keep the track support system in the linear conditions.