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دانلود مقالات تخصصی انگلیسی شاخه مهندسی راه و راه آهن رفتن به صفحه : قبلی  1, 2, 3 ... , 20, 21, 22  بعدی
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عضو شده در: 7 مهر 1385
پست: 37412

تشکر: 3351
تشکر شده 18468 بار در 8611 پست

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امتیاز: 210699
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پست تاریخ: چهار‌شنبه 27 خرداد 1394 - 18:20    عنوان:   پاسخگویی به این موضوع بهمراه نقل قول

Designing granular layers for railway tracks using ray optimization algorithm
2015
M. Esmaeili|J.A. Zakeri|A. Kaveh|A. Bakhtiary|M. Khayatazad
Abstract :
In this paper, the recently developed meta-heuristic algorithm, named Ray Optimization (RO), was applied to optimize the thickness of granular layers in railwaytracks. RO is a multi-agent algorithm, each agent of which is modeled as a ray of light that moves in the search space in order to nd global or near-global optimum solutions. To utilize RO, considering structural and serviceability constraints, rst, hypothetical values of three thicknesses were assigned to the layers. Then, stresses under the sleeper and on the subgrade layer were compared with the allowable values. The total minimum thickness of the layers was also compared with possible minimum thickness (serviceability constraint) and then minimum thickness values were selected. Optimization results showed that the moment of inertia of the rail had no signi cant impact on the minimum total thickness of the ballast and sub-ballast layers. On the other hand, train speed and axle load were the parameters that had a considerable e ect on the minimum total thickness of granular layers in the railway track.
Keywords :
Ray optimization; Design of ballasted railway tracks; Meta-heuristic algorithm; Granular layers; Minimum thickness of ballast layer
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عضو شده در: 7 مهر 1385
پست: 37412

تشکر: 3351
تشکر شده 18468 بار در 8611 پست

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امتیاز: 210699
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پست تاریخ: چهار‌شنبه 27 خرداد 1394 - 18:44    عنوان:   پاسخگویی به این موضوع بهمراه نقل قول

Experimental study on modeI fracture toughness of different asphalt mixtures
2015
M.R.M. Aliha|H. Behbahani|H. Fazaeli|M.H. Rezaifar
Abstract :
Low temperature cracking is one of the main distresses observed in pavements made of hot mix asphalt mixtures. As a material property, the fracture toughness of asphalt pavements is a fundamental parameter for estimating the load bearing capacity and resistance of cracked pavements against crack growth. In this paper, the fracture toughness (KIc) of different andvarious compositions of asphalt mixtures is obtained experimentally and the effects of asphalt characteristic specifications and its composition are investigated on the value of KIc. Several asphalt mixtures were prepared with three aggregate sizes, two aggregate types (limestone and siliceous), different air void percentages ranging from 3.5 to 8% and two binders (60/70 and 85/100). Other similar works have only studied the influence of limited characteristic parameters on the low temperature fracture resistance of asphalt mixtures. Several semi-circular bend (SCB) specimens subjected to three point bend loading were manufactured with different compositions and then were tested at -15oC. The experimental results showed the noticeable influence of characteristic specifications of asphalt mixtures on the value of KIc. Generally, the value of KIc decreases for those mixtures containing smaller size of aggregates made of siliceous with higher percentages of air voids and softer binder types.
Keywords :
Asphalt mixture, Low temperature, Fracture toughness, Characteristic specifications, Experimental study
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عضو شده در: 7 مهر 1385
پست: 37412

تشکر: 3351
تشکر شده 18468 بار در 8611 پست

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امتیاز: 210699
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پست تاریخ: چهار‌شنبه 27 خرداد 1394 - 23:04    عنوان:   پاسخگویی به این موضوع بهمراه نقل قول

Investigating on Vehicle-Slab Track Interaction Considering Random track bed Stiffness
2014
Mohammad Mehrali|Saeed Mohammadzadeh|Morteza Esmaeili|Mehrdad Nouri
Abstract :
This paper deals with the modeling of a vertically coupled vehicle-slab track using finite element method. The slab track system is represented by a two layer Euler-Bernoulli beam model including rail and concrete slab. The vertical stiffness of track bed is assumed to be random variable using Monte Carlo simulation. The vehicle is simplified as a multi-body system with 10 degrees of freedom. The accuracy of the simulation is verified by deterministic and random approaches as well. Sensitivity analyses onthe various parameters such as slab thickness, coefficient of track bed stiffness, vehicle velocity are perofrmed. It is demonstrated that the uncertainty in track bed stiffness has a major effect on rail and slab deflections. From a practical point of view, the obtained results of the present study can be utilized efficiently in the analysis and design of slab track systems.
Keywords :
vehicle-slab track interaction, random stiffness, Monte Carlo simulation,two layer Euler-Bernoulli beam
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مرجع کاربردی طراحی سازه های فولادی با نرم افزار ETABS 2013 و SAFE ورژن 12 : http://goo.gl/zkqFfH

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عضو شده در: 7 مهر 1385
پست: 37412

تشکر: 3351
تشکر شده 18468 بار در 8611 پست

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امتیاز: 210699
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پست تاریخ: چهار‌شنبه 27 خرداد 1394 - 23:09    عنوان:   پاسخگویی به این موضوع بهمراه نقل قول

Comparing lateral resistance to different types of sleeper in ballasted railway tracks
2014
J.A. Zakeri|A. Bakhtiary
Abstract :
Identifying the contribution of each part of the railway to total lateral resistance is considered the most important issue in choosing type of sleeper for providing lateral stability of ballasted railway track. On the other hand, identifying the percentage of effect of each part can help to present new methods for increasing lateral resistance of ballasted railway track. Methodology of this study was based on experimental work in the laboratory. In this paper, the contribution of each part of the sleeper comprised of base, crib and shoulder was determined in the total lateral resistance by STPT tests. In all of the measurements, thegreatest value of lateral resistance was related to the area under the sleeper (base zone) and its corresponding valuesin concrete, steel and wood sleepers were62%, 56% and 51%, respectively. The contributionsof shoulder and crib area to the lateral resistance were28% and 9% for concrete sleeper, 27% and 22% for wooden sleeper and 18% and 26% for steel sleeper, respectively.
Keywords :
Lateral resistance of railway; ordinary concrete sleeper; steel sleeper; wooden sleeper.
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_________________
مرجع کاربردی طراحی سازه های فولادی با نرم افزار ETABS 2013 و SAFE ورژن 12 : http://goo.gl/zkqFfH

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عضو شده در: 7 مهر 1385
پست: 37412

تشکر: 3351
تشکر شده 18468 بار در 8611 پست

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امتیاز: 210699
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پست تاریخ: چهار‌شنبه 27 خرداد 1394 - 23:33    عنوان:   پاسخگویی به این موضوع بهمراه نقل قول

Rheological master curves for modified asphalt binders
2013
Seyed Mohammad Asgharzadeh|Nader Tabatabaee
Abstract :
Modified bitumen enhances the performance properties of asphalt mixtures. A number of studies in the last decade have evaluated the performance properties of modified binders at different service temperatures. It is however possible to evaluate some modified binder time-temperature characteristics and performance properties through their rheological master curves. In this research, styrene butadiene styrene, ethylene vinyl acetate, polyphosphoric acid and crumb rubber were used to modify a PG58-22 base binder. Rheological master curves for |G*| and phase angles of these binders were generated using data from the dynamic shear rheometerand bending beam rheometerat temperatures ranging from -30℃to about 88℃. The rheological interpretation of the results indicated improved high and low temperature properties and reduced temperature susceptibility for most of the modified binders. A comparison of the modified binders was done based on the visual inspection of master curves for different temperature ranges.
Keywords :
Modified binder, Complex modulus, Phase angle, Rheological master curve, Pavement performance
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_________________
مرجع کاربردی طراحی سازه های فولادی با نرم افزار ETABS 2013 و SAFE ورژن 12 : http://goo.gl/zkqFfH

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عضو شده در: 7 مهر 1385
پست: 37412

تشکر: 3351
تشکر شده 18468 بار در 8611 پست

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امتیاز: 210699
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پست تاریخ: پنج‌شنبه 4 تیر 1394 - 22:42    عنوان:   پاسخگویی به این موضوع بهمراه نقل قول

Stabilization of Subgrade Soil for Highway by Recycled Polyester Fiber
Article 7, Volume 2, Issue 1, Winter 2014, Page 93-105 XML PDF (702 K)
Authors
Foad Changizi* ; Abdolhosein Haddad
Department of civil Engineering, Semnan University, Semnan, Iran
Abstract
Subgrade soil stabilization is one of the primary and major processes in the construction of any highway; also environmental authorities are concerned about the growing amount of polyethylene (PET) bottles produced by household sectors. This research in order to study effect of adding recycled polyester fiber on soil engineering properties, especially shear strength and California Bearing Ratio (CBR) used clay soil with low liquid limit (CL) and atterberg limits used high liquid limit (CH). Clay soil with recycled polyester fibers are mixed with soil in three different percentages 0.1%, 0.3% & 0.5% (the portion of stabilizer matters to soil net weight). Shear strength, CBR, atterberg limits of stabilizer samples were measured by direct shear test and CBR test and atterberg limits test. Experiments results show this fact that using of recycled polyester leads to increasing shear strength and CBR and reduction, plasticity index. It is remarkable that according to economic problems, the most optimum quantity of recycled polyester fiber to reach to favorite strength is 0.5%.
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عضو شده در: 7 مهر 1385
پست: 37412

تشکر: 3351
تشکر شده 18468 بار در 8611 پست

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امتیاز: 210699
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پست تاریخ: پنج‌شنبه 4 تیر 1394 - 23:03    عنوان:   پاسخگویی به این موضوع بهمراه نقل قول

Static and Dynamic Analyses of Micropiles to Reinforce the High Railway Embankments on Loose Beds
Article 7, Volume 1, Issue 2, Summer 2013, Page 80-89 XML PDF (849 K)
Authors
1M. Esmaeili; 1M. Gharouni Nik; 2F. Khayyer
1Assistant Professor, School of Railway Engineering, Iran University of Science and Technology, 16846 Iran, Tehran, Narmak
2M.Sc., School of Railway Engineering, Iran University of Science and Technology, 16846 Iran, Tehran, Narmak
Abstract
Construction of railway embankments on loose beds without using any methods of soil improvement (e.g. stone columns in silt and clay beds, deep soil mixing method, jet grouting and also using micropiles individually or in groups form) leads to reduction of embankment slope gradient, which significantly increases the volume of soil operation. Generally, micropile as a reinforcing element with the main characteristics of improving the mechanical-physical properties of soil, is a proper methodology for the aim of improving loose earth with low bearing capacity and intensive settlement characteristics. This paper explores numerical models of non-reinforced and reinforced railway embankments (with the height of 10 to 25 m) rested on loose beds that simulated and analyzed by SLIDE software. It should be considered that in order to reinforce the embankments using different arrangements of micropiles. In addition, the non-reinforced and reinforced embankments were analyzed against different load combinations that consist of railway operational load, permanent weight of the rail line and intense earthquake load. It should be mentioned that LM71 standard load was used as operational load during the simulations. The main purpose of this paper is finding the optimum arrangement of micropiles to reinforce the high railway embankments on loose beds. Therefore, according numerical analyses procedure, it was resulted that the use of micropiles exactly between toe and 1/3 to 1/2 length of the embankment slope is the optimal way to reinforce the embankments on loose beds.
Keywords
Micropiles; Numerical modeling; Embankment; Loose beds; Bearing capacity
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عضو شده در: 7 مهر 1385
پست: 37412

تشکر: 3351
تشکر شده 18468 بار در 8611 پست

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امتیاز: 210699
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پست تاریخ: پنج‌شنبه 4 تیر 1394 - 23:08    عنوان:   پاسخگویی به این موضوع بهمراه نقل قول

The Effect of Asphalt Concrete Micro & Macro Texture on Skid Resistance
Article 2, Volume 1, Issue 1, Winter 2013, Page 15-28 XML PDF (1265 K)
Document Type: Regular Paper
Authors
1M.R. Ahadi ; 2K. Nasirahmadi
1Assistant Professor, Road Safety Dept., Transportation Research Institute, Iran University of Science & Technology (IUST), Tehran, Iran
2M.Sc., Graduate, Highways & Transportation, Tehran, Iran
Abstract
Skid resistance and road condition are common indices of road safety; therefore providing adequate skidding resistance will reduce the incidence of road accidents. The surface macrotexture has a large effect on the characteristics of road surface skidding, which is the focus of this research. During the study, the mean texture depth of the road surface was measured, in order to determine the conditions that ensure the maximum contact area between the vehicle tires and road surface during wet conditions. The Pavement Guideline No. 234 was consulted for the test procedure and road surface composition, which used open and dense graded crushed lime aggregates with varying percentages of bitumen applied to the mix design. The samples were then tested to assess their stability using the Marshall and Gyratory Tests. The results showed that with the application and evaluation of the sand patch method, where the effect of the macrotexture on skidding resistance was analyzed with various gradations, there was an improved higher skidding resistance and a subsequent projected reduction of accidents with an increased safety.
Keywords
Safety; Skid Resistance; Micro & Macro Texture; Sand Patch; British Pendulum Tester
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عضو شده در: 7 مهر 1385
پست: 37412

تشکر: 3351
تشکر شده 18468 بار در 8611 پست

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امتیاز: 210699
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پست تاریخ: چهار‌شنبه 10 تیر 1394 - 00:38    عنوان:   پاسخگویی به این موضوع بهمراه نقل قول

BEHAVIOR OF FLEXIBLE PAVEMENTS ON EXPANSIVE SOILS

Author(s): DJELLALI ADEL*, OUNIS ABDELHAFID, SAGHAFI BEHROOZ

* CIVIL ENGINEERING AND HYDRAULIC DEPARTMENT, UNIVERSITY OF MOHAMED KHIDER, BISKRA, ALGERIA
Journal: INTERNATIONAL JOURNAL OF TRANSPORTATION ENGINEERING WINTER 2012 , Volume 1 , Number 1; Page(s) 1 To 14.
Abstract:
This investigation discusses the findings on analysis results of a pavement structure constructed on a relatively expansive material consisting mainly of brown clayey silt in Tebessa, Algeria. Cores were taken to laboratory from a piece of roadwork. Remolded samples were taken from subgrade of a deteriorated road. The soils were generally found to be of medium plasticity and of a medium to high expansion potential. Oedometer test for free swell indicated a constant volume pressure that produced stress in excess of 350 kN/m2. The following involves description of the behavioral characteristics of expansive soil as it relates to flexible pavements. Computer code Plaxis 8.2 was used for numerical simulation to check the behavior of structure pavement with three models in pavement structure, and free expansion test was performed to calibrate the soil subgrade with Soft-Soil Model. The results showed that the combined model Mohr-Coulomb in the pavement structure and the Soft-Soil in subgrade accord perfectly with deformations taken on the existing pavement. To stabilize the swelling character of subgrade, an adequate surcharge pressure is used according to the procedure described in the paper. It showed that after 9 months, the deformations have been stabilized at -0.007 m without any cracks in the pavement.

Keyword(s): FLEXIBLE PAVEMENTS, EXPANSIVE SUBGRADES, SOIL CALIBRATION, OEDOMETER TEST, SOIL BEHAVIOR, FINITE ELEMENT METHOD
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مرجع کاربردی طراحی سازه های فولادی با نرم افزار ETABS 2013 و SAFE ورژن 12 : http://goo.gl/zkqFfH

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عضو شده در: 7 مهر 1385
پست: 37412

تشکر: 3351
تشکر شده 18468 بار در 8611 پست

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امتیاز: 210699
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پست تاریخ: چهار‌شنبه 10 تیر 1394 - 01:01    عنوان:   پاسخگویی به این موضوع بهمراه نقل قول

ASPHALT PAVEMENT PERFORMANCE MODEL OF AIRPORT USING MICROWAVE REMOTE SENSING SATELLITE

Author(s): SUANPAGA WEERAKASET*

* DEPARTMENT OF CIVIL ENGINEERING, FACULTY OF ENGINEERING, KASETSART UNIVERSITY, BANGKOK, THAILAND
Journal: INTERNATIONAL JOURNAL OF TRANSPORTATION ENGINEERING WINTER 2012 , Volume 1 , Number 1; Page(s) 59 To 67.
Abstract:
The purpose of this study is to build the binary logit model of an airport pavement that could monitor the pavement condition in near real time using microwave remote sensing satellite, then the relationship between the international roughness index (IRI) of an airport and backscattering values from PALSAR images of the ALOS satellite was determined. Total 390 data were used in analysis. This model could be applied to evaluate the efficiency of the quality of running service on the airport pavement. The analysis showed that the backscattering values in the HH and HV polarization have correlated with IRI, and HH polarization was the highest correlation with IRI value (r=0.90). If the backscattering value in HH polarization is increased, the roughness will be increased. After the validation process on other 100 data, the result presented high correlation at 94.00%. Therefore, it can be concluded that this model could be applied to the airport pavement maintenance.

Keyword(s): PALSAR, AIRPORT PAVEMENT, BINARY LOGIT, IRI, MICROWAVE REMOTE SENSING
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