Consequence of stiffness and damping coefficients of suspension system on critical speed of a rail vehicle running on straight and curved track
سید
هادی یوسفی
دانشگاه علم و صنعت، دانشکده مهندسی راه آهن
author
text
article
2013
per
One of the most important cases in moving of trains especially in high speed trains is critical speed on straight and curved track. Generally for investigation of critical speed in railway vehicles, wheelset, bogie and or car body can be analyzed separately. In this paper a four axle rail vehicle is considered and equations of motion for complete vehicle and its single two axle bogie are derived separately on curved track. A computer program is developed in MATLAB software and these equations are solved in time domain and the critical speed is determined using response method. Effect of stiffness and damping coefficients of primary and secondary suspension system has been investigated on critical speed for the complete vehicle model and comprised with its single bogie model. Also, the effect of car body mass, wheel conicity and radius and also curve radius on critical speed have been studied. After analyzing of equations and obtaining graphs, it has been shown that changing of damping coefficient has more effect on critical speed than changing of stiffness coefficient. Increasing the radius of wheelset doesn’t have significant effect on critical speed. Also, decreasing of wheel conicity, increases stability but also it increases corrosion.
Journal of Transportation Research
مرکز تحقیقات راه ، مسکن و شهرسازی
1735-3459
10
v.
3
no.
2013
https://www.trijournal.ir/article_11491_d41d8cd98f00b204e9800998ecf8427e.pdf
Finite element analysis of fracture mechanics and contact mechanics of wheel-rail
سید
یوسف احمدی بروغنی
بیرجند، مهندسی
author
text
article
2013
per
In this paper, wheel-rail contact problem in presence of rail surface crack is investigated. The reason for investigating this problem is significant effect of wheel-rail contact on stress intensity factors and also the effect of crack on contact pressure distribution. In this research by using finite element method and a commercial software, wheel-rail are modeled under partial slip rolling condition. Contact elements are used to model the interactions between the wheel-rail contact surfaces and the crack surfaces. Stress intensity factors are calculated through a numerical displacement extrapolation method. The effects of crack orientation, crack length and contact on the stress intensity factors and contact pressure are studied. The results indicate that KII has greater than KI, therefore, shear mode may dominate the tip behavior in this wheel-rail contact problem. as the wheel passes over, the complicated crack edge deformation changes the direction of interfacial shear stress and this causes variation in KII. Fluctuation in KII is the main factor of fatigue crack propagation in the wheel-rail contact problem. The contact pressure is singular when the crack is located in wheel-rail contact zone. Hence, the assumptions of Hertzian contact pressure may not be valid when investigating wheel-rail contacts in the vicinity of a crack.
Journal of Transportation Research
مرکز تحقیقات راه ، مسکن و شهرسازی
1735-3459
10
v.
3
no.
2013
https://www.trijournal.ir/article_11492_d41d8cd98f00b204e9800998ecf8427e.pdf
The optimal aircraft size and economies of scale and stage length in Iran Air domestic routes
Hamid
Kordbacheh
دانشگاه الزهرا، دانشکده علوم اجتماعی، گروه اقتصاد
author
مهدی
پدرام
الزهرا، علوم اجتماعی و اقتصاد
author
شیرین
احمدیان چاشمی
الزهرا، علوم اجتماعی و اقتصاد
author
text
article
2013
per
This study examines the relationship between aircraft cost and size of commercial passenger jets for IranAir in its selected domestic routes over the period 2005-2008. Based on a translog model, we used an econometric cost function developed by Wei and Hansen (2003) for aircraft operating cost to investigate economies of scale and stage length and to measure the optimal size for the domestic services.
The finding of this paper show that economies of aircraft size and stage lengths exist at the sample mean of the sampled data. Evidence bears out the hypothesis that for any specified stage length there is an optimal size, in which aircraft optimal size in the short-haul market is always smaller than the least-cost aircraft size in the long-haul market, and as market distance increases, so does the size of the least-cost aircraft. The results also suggest that in shorter market the least-cost aircraft size is always smaller than the observed average aircraft whereas in long-haul market it is larger than the observed size. The findings also indicate that the scale properties of the cost function are not changed if pilot unit cost is treated as endogenous, since it is correlated with size.
Journal of Transportation Research
مرکز تحقیقات راه ، مسکن و شهرسازی
1735-3459
10
v.
3
no.
2013
https://www.trijournal.ir/article_11493_d41d8cd98f00b204e9800998ecf8427e.pdf
Determining the optimum number of truck processing booths in BIK dry- bulk terminal using queuing theory
سید
ناصر سعیدی
علوم و فنون دریایی خرمشهر، اقتصاد و مدیریت دریا
author
منصور
کیانی مقدم
دریانوردی و علوم دریایی چابهار، مدیریت و علوم انسانی
author
منصور
کیانی مقدم
دریانوردی و علوم دریایی چابهار، مدیریت و علوم انسانی
author
text
article
2013
per
The aim of this paper is to determine the optimum number of truck processing booths in the BIK dry-bulk terminal entrance gate, to reduce the associated truck congestions. The queuing theory has been used to gain this purpose. Since, the queuing theory is one of the appropriate methods to study traffics and congestions. The necessary data to analyze system performance analysis factors and to determine the pattern of inter arrival and service times are collected by several field studies. Descriptive statics showed, both inter arrival and service times follow exponential distribution. Then, the M/M/s queuing model has been developed for this port. Further, the K-S and χ2 goodness of fit tests has also demonstrated the suitability of model development. Then, the related system performance measurements have been determined. The performance measurements analysis showed a very high sensitiveness for this system and every change in the number of servers caused great impact on the system utilization and performance.
Journal of Transportation Research
مرکز تحقیقات راه ، مسکن و شهرسازی
1735-3459
10
v.
3
no.
2013
https://www.trijournal.ir/article_11494_d41d8cd98f00b204e9800998ecf8427e.pdf
Modelling and Solving Time Dependent Vehicle Routing Problem with Semi Soft Time Windows in Multigraphs
مجید
حبیبی
صنعتی خواجه نصیرالدین طوسی، مهندسی صنایع
author
حسین
کریمی
صنعتی خواجه نصیرالدین طوسی، مهندسی صنایع
author
text
article
2013
per
In the traditional “Time dependent Vehicle Routing Problems”, it is assumed there is only one edge between two nodes. In other words, these are designed based on a simple graph. However, in many urban areas, where there is complex urbanism and different traffic constraints and conditions, traditional VRP viewpoint is not very suitable.
In this article, an extension of the Time Dependent Vehicle Routing Problem (TDVRP) is studied, where more than one edge between the depot and customers and between customers is possible. The multigraph is a graph which is permitted to have multiple edges or parallel edges. Today, many of the transportation networks are defined in multiple graphs. Given the importance of FIFO property, it must be ensured. In this article, This is done using a special process. We proposed a model that is called “TDVRPMSSTW”. In this model, Semi Soft Time Windows is defined for customers. This formulation minimizes the total travel time, Time Window penalties and vehicle fixed cost.
Time Dependent Vehicle Routing Problem is an extension of Vehicle Routing Problem and since VRP is a NP-hard problem, therefore TDVRP is NP-hard too. So heuristics is used usually to solving these problems. In here, a Tabu Search (TS) algorithm is suggested for solving proposed model. The main feature of the proposed heuristic is randomly selection between two switching strategies in every stage of neighborhood search. These two strategies are binary switching and reverse switching. This feature improves the algorithm performance.
Finally, computational results of proposed Tabu search algorithm and the exact solution using GAMS software on the 40 designed instances are compared. These instances cover a good range of different problems with small dimensions. This result presents the efficiency of the proposed algorithm in computational time and quality of the solution.
Journal of Transportation Research
مرکز تحقیقات راه ، مسکن و شهرسازی
1735-3459
10
v.
3
no.
2013
https://www.trijournal.ir/article_11495_d41d8cd98f00b204e9800998ecf8427e.pdf
Analysis of the relationship between speed and density in heterogeneous traffic flow on suburban highways
علیرضا
سرکار
علم وصنعت ایران، عمران
author
رضا
عرفانی نسب
علم وصنعت ایران، عمران
author
text
article
2013
per
Over the past seventy years, several studies have been done about the relationship between macroscopic parameters of traffic flow. Based on Highway Capacity Manual (HCM), calibration of relations with parameters according with the conditions of each region is required.This study investigated the relationship between speed and density based on real data analysis for the heterogeneous traffic flow.In this regard, first the values of speed and density through each time periods calculated with a separation of line and vehicle class using data extracted from the loop detector installed in two 3-lane suburban Highways.On the other hand, the adaption of existing mixed-flow data with models Presented by Green Shields, Greenberg and Andrei Wood had been evaluated, and Results in very low adaptation rate.In the next step, using the general form of these models (linear, logarithmic, and exponential equations) we developed them for multi-class flow with considering line and day as constant parameters and density of each vehicle classes as variables.The stepwise regression procedure is used in this study as analysis method. Assumptions of regression model, such as examining the multicolinearity of variables, significant level of correlation factors, and Durbin Watson test was investigated.
At last, using the mentioned statistical tests, the best fitting model has been selected and sensitivity analysis was performed to examining different classes of vehicles affecting on speed variations of passenger car.
Journal of Transportation Research
مرکز تحقیقات راه ، مسکن و شهرسازی
1735-3459
10
v.
3
no.
2013
https://www.trijournal.ir/article_11496_d41d8cd98f00b204e9800998ecf8427e.pdf
Effect of cement and lime on performance properties cold recycling asphalt mixtures with SBS modified emulsion
حسن
زیاری
دانشگاه علم و صنعت، دانشکده عمران
author
رضوان
باباگلی
دانشگاه علم و صنعت، دانشکده عمران
author
رضوان
باباگلی
دانشگاه علم و صنعت، دانشکده عمران
author
حسن
زیاری
دانشگاه علم و صنعت، دانشکده عمران
author
text
article
2013
per
All over the world there are many projects used bitumen emulsion for cold in-place recycling (CIR) with good results. However, some emulsion CIR projects reported rutting, thermal cracking and asphalt stripping problems, caused to use additives to decrease rutting and emulsion CIR pavement distresses.
Since limited researches have been conducted to investigate the effect of additives on the recycled asphalt mixtures properties, in this research cement and lime used as additives in CIR mixtures. We used cement and lime in the form of powder and SBS as additive with or without cement and lime to evaluate the effect of each additive on the mechanical properties such as Marshall stability, durability, resilient modulus and permanent deformation.
Result indicate that SBS, cement and lime increase Marshall Stability, Resilient Modulus, moisture resistance and resistance to permanent deformation. Furthermore, mixtures which contain both cement and SBS have better results.
Journal of Transportation Research
مرکز تحقیقات راه ، مسکن و شهرسازی
1735-3459
10
v.
3
no.
2013
https://www.trijournal.ir/article_11497_d41d8cd98f00b204e9800998ecf8427e.pdf
Modeling gasoline demand in land transport sector in Iran by using GMDH neural network
حسین
صادقی
تربیت مدرس، مدیریت و اقتصاد
author
محمود
حقانی و مسعود اکبری
دانشگاه صنعت آب و برق، اقتصاد
author
text
article
2013
per
Gasoline is one of the main energy carriers in land transport sector. With regard to the low price for gasoline in Iran, the study of the non-price factors which affect gasoline demand is important.
In this paper, for identifying the most important factors which affect on gasoline demand, GMDH neural network model as a tool with high capacity in the diagnosis of non-linier complicated processes especially with limited number of observations is used.
At first, in a primary model, the effects of 10 variables which are titled inside and outside of system variables, on the demand for gasoline during 1387-1355 are evaluated. Then by using deductive process in the three stages, 5 variables identify as more important variables.
In the final stage, the variables such as gross domestic product per capita, the numbers of vehicles (with gasoline fuel), the gasoline subsidies and the foreign exchange rate in unofficial market have double and liquidity has normal influence on gasoline demand.
In addition to the
In addition, the results show that the importation of variables such as foreign exchange rate, liquidity and gasoline subsidies in the model increase the model efficiency.
Journal of Transportation Research
مرکز تحقیقات راه ، مسکن و شهرسازی
1735-3459
10
v.
3
no.
2013
https://www.trijournal.ir/article_11498_d41d8cd98f00b204e9800998ecf8427e.pdf
Analysis of the spatial and temporal climatic disasters affecting the road
مجید
وظیفه دوست
گیلان، پژوهشکده هواشناسی
author
میترا
لاله سیاه
پژوهشکده هواشناسی، پژوهشکده هواشناسی
author
text
article
2013
per
The human factor, vehicle, road and environment are involved in accidents that the environmental factors and climate phenomena to account for a significant share. The risk of weather affecting road transport, Thunderstorm storms can occur, Heavy rains and flash floods, dust storms, Fog and falling snow and avalanches noted that the slippery road surface, Reduce driver visibility and focus on the occurrence of road accidents increase. The assessment and analysis of the frequency of occurrence and geographical factors threatening the transport network and road Installation of safety equipment in critical areas can greatly reduce the occurrence of such accidents. In this study, the frequency of occurrence of weather phenomena affecting road transport and highways and major roads in the entire country. Using data collected from weather stations across the country and synoptic data from meteorological satellites was studied. Phenomena of weather and climate disasters and the types of indicators were used to identify them: Heavy precipitation (rainfall less than 30 mm high and 90 th percentile precipitation), Ice (start, end, duration and frequency of frost occurrence), thunderstorm wind (direction and speed and the frequency of occurrence of winds), Dust storm (dust phenomenon aerosol optical thickness), fog (visibility less than 1 km and the frequency of occurrence of short-clouds), flooding (flood rate rise basin) and snow and avalanches (frequency of occurrence of snowfall) . Spatial analysis of climate data and hazard zonation using ARCGIS software interpolation methods were used in and Highways and main roads in the country in terms of climatic disasters and the degree of risk they were classified. Also, to facilitate comprehensive and timely information, the information layer, designing a web-based software by Internet portals such as WISroGIS It was loaded into a live Atlas hospitalized for easy access to contents provided Atlas.
Journal of Transportation Research
مرکز تحقیقات راه ، مسکن و شهرسازی
1735-3459
10
v.
3
no.
2013
https://www.trijournal.ir/article_11499_d41d8cd98f00b204e9800998ecf8427e.pdf