فهرست مطالب

  • سال سوم شماره 2 (پیاپی 7، تابستان 1385)
  • تاریخ انتشار: 1385/07/20
  • تعداد عناوین: 6
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  • شهریار افندی زاده، مرتضی شاه نظری صفحه 75

    یکی از مباحث مهم بخش حمل و نقل، تعیین مقدار حمل بهینه کالاهای وارداتی از مبادی ورودی به مناطق مختلف مصرف است. در این تحقیق با شناخت عوامل تعیین کننده تقاضای جاده ای، اقدام به تدوین مدل برنامه ریزی خطی به منظور معرفی مقادیر بهینه حمل کالاهای وارداتی از مبادی ورودی به مراکز مصرف شده و هدف از آن کمینه کردن کل هزینه های حمل و نقل است.
    از آنجا که سهم واردات کالا از مرزهای آبی بیش از 94 درصد است. بنادر به عنوان مبادی ورودی کشور در نظر گرفته شده اند. سپس زمینه های نظری روش برنامه ریزی خطی (LP)، خصوصیات و فرضهای اساسی برنامه ریزی خطی، شیوه ساخت مدل و مدل عمومی ریاضی در برنامه ریزی خطی مشخص شده و روش ساخت مدل عرضه و تقاضا ارایه می شود. همچنین برای منطقه بندی انتخابی در این تحقیق با توجه به عوامل مهم از قبیل جمعیت، شبکه توزیع، موقعیت جغرافیایی استانها، وضع موجود شبکه راه های استانی و نرخ خدمات رسانی حمل و نقل، استانهای کشور به عنوان مراکز مصرف در نظر گرفته شده اند. ضرایب تابع هدف در مدل تقاضا، کرایه حمل مبدا - مقصد کالا هستند و در توابع قید نیز ظرفیت هر یک از مبادی ورودی و نیاز هر استان از کل واردات کشور ضرایب توابع هستند. این ارقام براساس اطلاعات سازمان راهداری و حمل و نقل جاده ای و سازمان بنادر و کشتیرانی استخراج شده اند. نهایتا به کمک روش برنامه ریزی خطی، مقادیری حمل بهینه کالاهای وارداتی از بنادر به مراکز استانها، مقدار استفاده از ظرفیت هر یک از مبادی، آنالیز حساسیت مربوط به مساله و قیمت های سایه مربوط به محدودیت ها و هزینه ها فرصت مشخص شده اند.

    کلیدواژگان: برنامه ریزی خطی، تقاضای کالا، عرضه کالا، شبکه حمل و نقل
  • فرهاد دانشجو، علیرضا قاری قرآن صفحه 85
    یکی از مهم ترین عوامل انهدام سازه پل هایی از نوع تیر و دال، بروز و رشد خسارت (آشکار یا پنهان) در اجزا روسازه آن ها در طی زمان است. در این مقاله تاثیر خسارت بر خواص دینامیکی شامل فرکانس طبیعی، میرایی، سختی خمشی و دامنه ارتعاش برای تیرهای بتن مسلح به عنوان یکی از رایج ترین عناصر مورد استفاده در این نوع پل ها از طریق انجام تحقیقات آزمایشگاهی بررسی شده است. خسارت با اعمال بار استاتیکی و ایجاد ترک خمشی برای یک تیر دو سر ساده بتنی مسلح تعریف شده است. از آنجا که درصد میرایی به خطی و غیرخطی بودن رفتار اجزا بسیار وابسته بوده و نیز سختی به میرایی مربوط است، با ایجاد نیروهای دینامیکی ضعیف توسط موتور ارتعاش، آزمایش های دینامیکی با حفظ رفتار خطی برای المان تیر انجام شده است. نتایج حاصل نشان می دهد که میرایی تیر در محدوده مقطع ترک خورده، میرایی لزج تنها نبوده و ترکیبی از میرایی لزج و اصطکاکی است و با اثر افزایش ترک یا خسارت سهم میرایی اصطکاکی افزایش می یابد. همچنین در این مقاله به جای استفاده از روش آزمایش های استاتیکی، دو روش برای ترسیم منحنی نیرو - جابه جایی و تعیین سختی تیر بتنی از طریق انجام آزمایش های دینامیکی ارایه می شود. یکی از این روش ها وابستگی کمتری به ضریب میرایی دارد. صحت و دقت هر دو روش به کمک آزمایش های انجام شده، به اثبات می رسد.
    کلیدواژگان: تعیین هویت دینامیکی، ارزیابی دینامیکی، تیر بتنی، خسارت، میرایی، پل
  • محمود صفارزاده، امیر کاووسی ومحمد باقری ساری صفحه 101
    به منظور مدیریت بهینه روسازی راه های موجود لازم است علاوه بر شاخص های اقتصادی، عوامل دیگری چون بهبود در شاخص های بهره برداری، بهبود در وضعیت سازه ای روسازی و تاثیرات گزینه ها بر محیط زیست، شرایط اجتماعی، ایمنی و... مدنظر قرار گرفته و در تصمیم گیری نقش داشته باشند. وارد نمودن موارد فوق در اولویت بندی گزینه ها، نیازمند یک تصمیم گیری چند معیاره است که در این مقاله مدلی براساس روش سلسله مراتبی (AHP) برای آن ارایه شده است.
    در این تحقیق با استفاده از فرآیند تحلیل سلسله مراتبی، مدلی برای مدیریت روسازی راه طراحی و ساخته شده است. در این مدل به منظور ارزیابی فنی و اقتصادی گزینه ها، ابتدا اطلاعات ورودی مورد نیاز نرم افزارهای ELMOD-5 و HDM-4 تهیه می شوند. سپس با بکارگیری نتایج به دست آمده از اجرای مدل، اولویت بندی گزینه های تعمیر و نگهداری و نهایتا تصمیم گیری برای انتخاب گزینه برتر، به روش تحلیل سلسله مراتبی (AHP) و با استفاده از نرم افزار Expert Choice انجام می شود.
    کلیدواژگان: مدیریت روسازی، مدیریت نگهداری راه، تحلیل سلسله مراتبی، تصمیم گیری چند معیاره و تعمیر و نگهداری راه
  • مرتضی قارونی نیک، رضا بری دیزجی، همایون کتیبه صفحه 111

    امروزه تهویه تونل های راه آهن در کشور ایران با توجه به قدمت آنها و نیز نیاز به افزایش ترافیک عبوری، بخصوص در نواحی غربی کشور از اهمیت ویژه ای برخوردار است. مهم ترین عوامل موثر در طراحی تهویه این تونل ها، گرما و گازهای حاصل از سوخت در موتورهای دیزل است. گرمای حاصل از احتراق موتور، ممکن است دمای هوای تونل را تا آن حد افزایش دهد که موتور لوکوموتیو نتواند با راندمان قابل قبولی کار کند. محصولات ناشی از احتراق سوخت نیز موجب آسیب افرادی خواهد شد که از تونل می گذرند. به این ترتیب سیستم تهویه این تونل ها را باید با توجه به این دو جنبه طراحی کرد. روش ارایه شده در این مقاله که اولین گام علمی و عملی در زمینه تهویه تونل های راه آهن موجود کشور است، بر مبنای استفاده از امکانات حمل و نقل ریلی فعلی و دستیابی به استاندارد سازی هوای مورد نیاز داخل تونل در حد مطلوب استوار است. بررسی روش های مختلف تهویه در این مقاله نشان می دهد که حفر دستکها یا چاه های متصل به تونل و انتقال هوا از طریق آنها و نیز نصب تجهیزات در داخل تونل، به علت عدم انجام مطالعات ژئوتکنیکی و در نتیجه عدم شناخت صحیح مصالح اطراف تونل، طولانی بودن مسیر حفاری دستکها و عدم وجود فضای کافی در داخل تونل از نظر فنی و اقتصادی مطلوب نیست و در نهایت روش نصب بادزن قوی در خارج تونل اصلی و نصب دروازه هوابند در داخل آن انتخاب شد. از مزایای این روش می توان به عدم تداخل کار در تعمیر و نگهداری بادزن ها با حرکت قطارها اشاره کرد.

    کلیدواژگان: تونلهای راه آهن، سیستم های تهویه، بادزن تهویه، دروازه هوابند
  • سید مرتضی مرندی، پروین صفاپور صفحه 123

    پروژه راه اصلی دوغارون - هرات به طول 122 کیلومتر به عنوان بخشی از کمک های نظام جمهوری اسلامی ایران به افغانستان اجرا گردیده است. با توجه به وضعیت خاص منطقه، کمبود مصالح مرغوب و بارگیری بیش از حد کامیونهای افغانی)حدود 70 تن در هر تریلر(، این جاده به صورت ویژه طراحی شده و به مرحله اجرا درآمد. در روسازی جاده مزبور از روش پیشرفته تثبیت لایه اساس با استفاده از سیمان و قیر امولسیون و همچنین ماشین آلات ویژه بهره گیری شده است. در طراحی این جاده از روش شل و نرم افزارهای PAVERS و PADS استفاده شده است. استفاده از ماشین آلات مخصوص جهت اجرای این جاده و بکارگیری از فناوری نوین تثبیت و کنترل کیفیت با دستگاه خیز سنج دینامیکی نشان می دهد که ظرفیت باربری لایه تثبیت شده بیش از دو برابر روش های سنتی بوده و افزون بر این سرعت اجرای عملیات به گونه ای محسوس هزینه های اجرایی را کاهش داده است.

    کلیدواژگان: سیمان و امولسیون قیر، خیز سنج دینامیکی، روش Shell، تثبیت
  • داود مستوفی نژاد، حامد حسین نظری منفرد صفحه 139
    دوام بتن های در مجاورت یون سولفات نظیر ابنیه موجود در مسیر راه ها و از جمله پایه های پل، از مسایلی است که همواره نگرانی ویژه ای به دنبال داشته است. در این تحقیق دوام بتن های حاوی سرباره و پودر سنگ آهک، در محیط های سولفات منیزیم 5 درصد، سولفات سدیم 5 درصد و آب خالص مورد بررسی قرار گرفت همچنین تاثیر عامل نوع یون سولفات در نسبت های مختلف آب، پودر سنگ آهک و سرباره به مواد سیمانی، به همراه پارامتر زمان، در کاهش وزن و کاهش مقاومت فشاری بررسی شد. به این منظور 27 طرح اختلاط، شامل بتن های حاوی 0، 15 و 30 درصد پودر سنگ آهک جایگزین سیمان در 3 حالت بدون سرباره، 10 درصد سرباره جایگزین سیمان و 20 درصد سرباره جایگزین سیمان در نظر گرفته شد. برای ساخت این بتن ها از سه نسبت آب به سیمان 0.3، 0.4 و 0.5 استفاده شد. نتایج این تحقیق که با انجام آزمایش بر روی 243 نمونه 70×70×70 میلیمتری در 2 زمان 70 و 140 روزه انجام شد، نشان داد که استفاده از ترکیب %10 سرباره و %15 پودر سنگ آهک جایگزین سیمان، ضمن اقتصادی کردن طرح مخلوط، سبب افزایش دوام بتن ها می شود. چنین ترکیبی از مواد سیمانی، برای ساخت بتن های در مجاورت یون سولفات و از جمله ابنیه مسیر راه پایه های پل توصیه می شود.
    کلیدواژگان: بتن، دوام، سرباره، پودر سنگ آهک، سولفات منیزیم، سولفات سدیم، پایه
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  • Sh. Afandizadeh, M. Shahnazari Page 75

    One of the main problems in transportation systems of various countries, specially in the recent years has been and will be the transport of imported goods from the entering origins towards the consumption areas. In this paper, by recognising the effective factors influencing the road transport demand in Iran, it has been tried to develop a linear programming model for calculation of the optimum values of transporting the imported goods from the origin points to the consumption centers. In fact, the problem is categorized as a problem of physical distribution of freights from several production sites to the consumption points. After solving this problem, a situation will be created by which the costs of distributing the imported goods is minimised.Regarding the high share of marine imports (94%) in the country, the southern and northern ports have been assumed as the entrance origins. Also due to the conditions of population, distribution network, geographical situation of the provinces, current provincial roads and the transportation service fares, the provincial capitals have been supposed as the destination or consumption centers. A background of the linear programming method, as well as its’ characteristics and assumptions and the method of a LP model construction will be explained and after that, the LP model will be applied to find the optimum values of transporting goods from origins toward destinations, and simultaneously to minimize the total costs of transport. The objective function coefficients for this LP model are the Origin-Destination fares of transportation. For the constraints of the LP model, capacities of the ports and also consumption values of the provinces have been supposed as the right hand sides. They have been extracted from the information provided by The Road Transportation and Terminals Organization, and The Ports and Shipping Organization, which both are governmental administrations working under the Iranian Ministry of Roads and Transportation. At last the problem is being solved and the best quantities of transport of goods between each O-D pair, as well as the amounts of capacity engagement in each origin port, sensitivity indices of the problem, and the shadow pieces for each constraint will be introduced.Results of this study show that the minimized total cost of this transportation system reaches to 3,156 billion Rials which has been obtained after 34 repeats of the Simplex method. Also it shows that the optimal pattern derives a situation in which not all the consumption centers should be assigned shares from all origins, but the current situation in the country is despite that; In fact, in the current situation, all the provinces are importing goods from all ports, and this is not optimal.

  • F. Daneshjoo, A. Gharighoran Page 85
    One of the major factors contributing to structure collapse is the appearance and development of damage (visible or concealed) in structural components by time. In this paper, the effect of damage on dynamic characteristics of reinforced concrete beams usable in bridges, including natural frequency, damping ratio, bending stiffness and vibration amplitude are experimentally investigated. Damage is considered as a reduction in the flexural stiffness by extension of the flexural cracks. The force-deformation curve becomes a linear curve (no hysteretic loop) if the cyclic load is applied slowly enough, hence in this experiments slow dynamic force is created by the vibration motor. The results indicate that the damping ratio in the vicinity of the cracked region is not merely a viscous damping, but rather is a combination of viscous and frictional damping, and the contribution of the frictional damping will increase by increasing the crack or damage. The natural frequency of beam and its maximum amplitude of vibration increase with increasing eccentric mass and therefore with increasing dynamic load. The damping ratio is significantly influenced by the degree of cracking, increase of eccentric and number of cycles. In general, damping ratio calculated by averaging the values for different cycles, increases with increasing degree of cracking and with increasing dynamic load. The results indicate that maximum amplitude of vibration, bending stiffness and natural frequency of beam decrease and damping ratio increases with increasing degree of cracking. Also, in this paper, two new extended methods for determining the stiffness of concrete beams using dynamic force-displacement curve instead of static experimentation methodology are presented. Precision and accuracy of the both proposed methods are verified. It is observable that the results related to the 2nd proposed method for dynamic secant stiffness curves have best correlation with the static stiffness curves. Results indicate that by increasing the number of cycles N in logarithmic decrement method, the dynamic force-displacement curve closes to the static force-displacement curve.
  • M. Saffarzadeh, A. Kavousi, M. Bagheri Sari Page 101
    To develop an optimal pavement management system, several factors such as economic indices, improved utilization parameters, improvement in structural situation of pavements and the effect of options on the environment, social and safety measures, etc…. should be considered. Inputting the above mentioned parameters into the priority chain of the determined options, requires a multi disciplinary decision making process. In this paper, a model on the basis of Analytical Hierarchy Process has been developed.In order to evaluate the technical and economic aspects of the model's options, first of all the input data required for Elmod-5 and HDM-4 programs is prepared. Prioritization of repair and maintenance options and finally decision making for determination of the preferred option is done by AHP and Expert Choice Software, using the results obtained from implementation of the model.The pavement management system is usually practiced in two network and project levels. In the pavement management at the network level, the priority of projects and the operations regarding their maintenance and time schedule is determined by the present limitations, while in the project level, the implementation of various methods of repair and maintenance for a specific project is evaluated and compared.In this research a model has been designed for the pavement management in which by using the Life Cycle Cost Analysis and the AHP, the prioritization of options and decision making about the pavement management is improved. The construction phases of the MPHS Model are as follows:- Supply of input data- Preliminary evaluation and segmentation of pavement- The preliminary selection of repair and maintenance options- Techno economic evaluation of options- Prioritization of options- Choice of maintenance method- The HDM–4 and ELMOD-5 software have been used for techno economic evaluation of the various options. The analytical framework of the HDM-4 Model is based on the Pavement Life Cycle Cost Analysis. This model is used for prediction of factors such as road destruction and ageing, effects of the road situation on utilization, effects of the road users, and finally environmental, technical and economic effects on the life cycle of a pavement which is usually 15-40 years. In the new model, on the basis of comprehensive literature review as well as the experiences of experts (direct interview), the most important factors for techno economic evaluation of options were selected. These factors include economic parameters, the comfort of vehicle's users, the structural stability and the drainage quality.In this research, the Western – Eastern route of Shahid Babaiee Expressway in Tehran was chosen as the case study and the pavement life cycle analysis for a period of twenty years was implemented.Using this model, the decision makers can choose the most suitable and optimal way for the improved management of pavements through changing the weight of decision measurements and recognition of the expert's experiences and viewpoints, using the group AHP Method.This study is illustrative of the fact that the criteria of "economic output" is the most important parameter affecting the repair and maintenance choice and then some other parameters like the comfort of the vehicles attendants, the quality of drainage and the structural stability are accordingly the other important parameters in decision making process. Therefore, none of the above mentioned factors can merely be the suitable criterion for the prioritization of options and the choice of the suitable maintenance method.
  • M. Gharouni Nik, R. Berry Dizaji, H. Katibeh, University Of Amirkabir Page 111

    Nowadays ventilation of railway tunnels in Iran with regard to their age and the need for increasing the traffic lines, especially for the west part of the country, is of paramount importance. The most important factors affecting ventilation design of these tunnels are heat and the gases produced by fuel combustion in diesel engines. The heat produced by these engines may increase the temperature of the air in tunnels so that locomotive motors are not able to operate with a reasonable efficiency. Products resulting from fuel combustion may also cause problems for the tunnel users. Therefore, ventilation of the tunnels should be designed with respect to these two aspects. The method presented in this paper, which is the first scientific and practical step in this regard, is based on using present railway transportation facilities and approaching standardization of the appropriate required air inside the tunnel. Studyin of different ventilation methods shows that excavation the galleries and connected shafts the air through which may be transferred, or installation of the equipment inside the tunnel are not technically and economically desirable due to lack of geotechnical surveys and therefore knowledge about the earth materials, elongation of the proposed galleries and shafts and finally lack of the clearance in tunnel. These considerations resulted in choosing the method of installing a powerful jetfan outside the tunnel and using the air-tight gates, one of the advantages of which is prevention of interference between the maintenance procedures with the train movement. In this paper the requirement for installation of ventilation facilities in the railway tunnels in Lorestan province in the west of Iran, with particular emphasis on the 102 Lorestan Railway Tunnel has been discussed. First of all the possibility of applying the different methods of ventilation in this tunnel was studied and according to the geometric conditions of the tunnel and topographical situation of the area, the possibility of using the hand dollies and access tunnels was disregarded. The transverse and semi transverse ventilation systems was not preferred either, due to the complexity of these systems compared to longitudinal ventilation systems.Finally application of strong fans with 130m3/s and the 3 KPa pressure and an engine with 600 KW power along with utilization of ventilation gallery with 50 m length and angle towards the main tunnel and airtight doors, has been selected as the optimal ventilation systems for this tunnel.

  • S.M. Marandi, P. Safapour Page 123

    Heart - Dogharoon main road project with 122 kilometers in length was constructed with international donation as a part of support to Afghanistan. Due to special condition in this area, lack of good quality material and over loading passing trucks (70 tons per trailer), this road was designed and executed with special consideration. For design of this road, stabilization method using emulsion bitumen and cement with related special equipments was used. PAVERS and PADS software programs were used to design the thickness of the layers. The quality of stabilized base layer was controlled by Falling Weight Deflectometer (FWD). The results showed that the bearing capacity of stabilized layer was more than twice amount of predicted figure.Also the execution time period was decreased considerably in compare withconventional method.To construct roads and runways with high bearing capacity and to increase the roads life time and bearing capacity for heavier loads, various methods are introduced. Methods such as improvement of pavement materials, increasing the layers thickness, renovation with soil stabilization and Cold Mix Recycling (CMR) using lime, cement, bitumen and etc. are used [3].Stabilization of materials using emulsion bitumen and cement is a method which introduces a proper way for aggregates improvement. The experiences show that, using emulsion bitumen has successfully increases the bearing capacity of roads and runways.Emulsion bitumen as a stabilizer material is used predominantly in recent years and due to its various benefits such as high bearing strength, environmental and economical goals and ease of use is admired by experts. Furthermore, using emulsion bitumen in cold recycling process has specific acceptability and popularity between the users [4].Emulsion bitumen with exclusive properties can be used in various quality aggregates and also soil materials with high plasticity index. Besides, one of the most uses of emulsion bitumen is in cold recycling process. High speed in performance, easy to work with emulsion bitumen producing plant, easy and quick compaction of produced layers, possibility of using traffic on the constructed layer immediately after construction, and economic and environmental advantages are attractive factors encouraging road builders and contractors to use emulsion bitumen.In this paper and in a study case, while the method of stabilization using emulsion bitumen and cement is introduced, design method, execution procedures and quality control of 122 kilometers main international transit road constructed in Afghanistan is presented and compared with conventional method from economical points of view. The benefits of this method, mix design procedures and related laboratory tests and pavement design are studied and analyzed precisely. The results show that, not only the bearing capacity is increased in comparison with conventional methods but, the execution period and consequently the costs are decreased considerably.At each stage of stabilization, various laboratory tests such as unconfined compression strength test, indirect tensile strength test, in situ and laboratory densities, moisture content and cement and bitumen emulsion contents were carried out. All tests showed that the results are acceptable and in cases, the results of bearing capacity were more than twice as much that was predicted.To determine the modulus of elasticity and to control the quality of the sections performed, a falling weight deflectometer machine was used. The measuring points were every 50 meters in both traffic lines. Back calculated modulus of elasticity of the sections 0 to 23, 23 to 32.3 and 35.3 to 44.4 kilometers of the Heart - Dogharoon main road were determined. The results showed that the average measured modulus of elasticity is more than twice the figure predicted (the predicted figure in design was 1500 N/mm2). It means, the bearing capacity of the sections performed, reached to an excellent result and satisfied the high limit of loading in that area.

  • D. Mostofinejad, H. H. Nazari Monfared Page 139
    Durability of concrete in the environments containing sulfate ion has been accompanied with special concern for many reinforced concrete structures such as bridge decks and piers. Such structures as well as many other reinforced concrete structures have been suffering from corrosion due to existence of sulfate ions in soil or water adjacent to structure. Conventional methods like use of sulfate resistance cement in concrete has been utilized for long time; however, due to its limited effect and its unsuitability against some other harsh environments, alternative solutions like substitute of pozzolanic materials with a part of cement has been attracting for many researchers and practical engineers.In the current study, to introduce a concrete with relatively high durability against sulfate ions, concretes containing slag and limestone powder were examined in sulfate environment. Since the concentration of sulfate ion in site is low and the corrosion of concrete adjacent to soil or water containing sulfate ion occurs during a long time, for evaluation of the effect of sulfate ion on concrete within a shorter period of time in the laboratory, it is necessary to perform accelerated experiments. The accelerator tests can be done by increasing the concentration of the sulfate ion and/or performing wetting and drying cycles on the concrete specimens. Accordingly, the solutions of 5% magnesium sulfate, 5% sodium sulfate and pure water were used as laboratory environments to perform the tests. To design the concrete mixes, ACI 363R was used to determine the ingredients; however according to ACI 211.4R-93, 30% reduction in water amount was utilized based on using super plasticizer in the mix. Liquid super plasticizer with Melamine base was used and the slump was stabilized about 80-100 mm. Besides the aforementioned codes, some modifications were made in the amount of solid ingredients based on the recommendations Mostofinejad and Nozhati. In order to evaluate the concrete deterioration process in sulfate ion, the reduction in compressive strength plus the weight changes in all specimens were measured; hence, the effect of the type of sulfate ion in different water-to-cement ratios and different ratios of limestone powder and slag on the decrease of weight and compressive strength of concrete was investigated. To do so, 27 mix designs including 15% and 30% substitute limestone powder and 10% and 20% substitute slag with the water-to-cement ratios of 0.3, 0.4 and 0.5 were made and cast in 243 cubes. The test results on the specimens after 70 and 140 days showed that a combination of 10% slag and 15% limestone powder substitute to cement not only provides an economical mix design, but also fairly increases the durability of concrete. Such a combination of cementitious materials could be recommended for concrete in sulfate environments; e.g. for construction of bridge piers.