Demiryolunda Balastsız Üstyapıların Hesabı Ve Lvt İçin Örnek Hatta Farklı Araç İşletimleri İçin Parametrik İrdelemeler

Abstract

Raylı sistemlerin çıkış noktası oldukça eskiye dayanmaktadır. Çok eski tarihlerde insanların ağır yüklerin taşınmasında bugünkü raylı sistemlere benzer şekilde taşımacılık yaptığı bilinmektedir. Günümüze gelinceye kadar raylı sistemde önemli gelişme sağlanmıştır. Motorlu araçların ortaya çıkışı ile birlikte sanayileşme ve hızlı nüfus artışı raylı sistemlere olan ihtiyacı gün geçtikçe artırmış ve modern demiryolları kurulmuştur. Bugün maglev trenlerle 500 km/h hızın üstüne çıkılmış, ancak maglev trenler henüz yaygınlaşmamıştır. Bilinen en yüksek hızda (max. 430 km/sa) işletme yapan tek maglev tren hattı Çin’de yolcu taşımasında kullanılmaktadır. Klasik demiryolu araçlarının hızı ise bugün 300 km/h’in üstüne çıkmış ve yolcu taşımacılığında önemli bir paya sahip olmuştur. Bütün bu gelişmeler demiryollarının insan hayatındaki yerini ve önemini artırmaktadır. Artan talebin karşılanmasına yönelik birçok çalışma yapılmış ve bunun soncunda çeşitli rijit üstyapı tipleri ortaya çıkmıştır. Bunların neticesinde hem insan hayatının güvenliği hem de uzun süre bozulmadan stabilitesini koruması ve uygun maliyetli olabilmesi açısından demiryolu üstyapı hesaplamaları önem kazanmıştır. Bu çalışmamızda 2. bölümde balastsız üstyapının avantajları anlatılmış ve dünyada kullanılan rijit üstyapı tipleri tanıtılmış ve üstyapı enkesitleri şekillerle açılanmıştır. 3. bölümde yerinde dökme üstyapıyı oluşturan raylar, bağlantı elemanları, traversler ve betonarme plaklar incelenmiş ve bu elemanlara ait dünyada kullanılan türler sınıflandırılarak anlatılmış ve teknik özellikleri, olumlu ve olumsuz yönleri hakkında bilgiler verilmiştir. 4. bölümde ise LVT üstyapısı ve bileşenleri daha detaylı bir şekilde açıklanarak kullanıdığı hat kısaca tanıtılmış, LVT sistemin seçilmesinde öne çıkan titreşim ve gürültü önlemlerine değinilmiştir. 5. bölümde; üstyapı boyutlandırılmasında kullanılan parametreler ve hesaplamaları anlatılmış, rijit üstyapı hesaplamasına örnek olarak LVT tipi üstyapının farklı araç işletim durumları için statik analizi yapılmış ve boyutlandırılması gerçekleştirilmiştir. Yapılan hesaplamalar sonucunda üstyapıya etki eden parametrelerin değişmesi durumunda analiz ve hesaplamalara dair görüşler son bölümde belirtilmiştir.

The origin of the railway systems is considerably old. In very old times, it is known that people were carrying heavy freights by the similar way in concept to railway transportation. From history to present day, there have been significant improvements in the rail system. With the industrial revolution and the appearance of motor vehicles together with the rapid population growth, the need of railway transportation gradually increased and that demands resulted in modern railway establishment. Today, maglev trains have been exceeded 500 km/h speed but this type of railway transportation is not in public use yet. Only one line of maglev train in China known in service carrying passengers with high-speed (maximum velocity is 430 km/h). On the other hand, conventional rapid trains recently have reached over 300 km/h velocity. These rapid trains nowadays have significant share of transportation in the world. Thanks to all these developments, the railway transportation has been taking more important place in human life. To fulfill the increased demands, many types of railway systems have been implementing and more passengers have been benefiting from railway transportation day by day. Therefore, to provide a secure and comfortable transportation system concurrently with favorable cost, railway track design becomes more prominent. In this study, 2nd chapter explains conventional railway and the layers of the railway track by giving technical properties. The layers that form the track superstructure are the formation, sub-ballast, ballast, geotextile, frost protection layer. Since the topic of this study is a ballastless track design, sub-ballast and ballast layers are not explained here. Add to this, brief information about sub-base soil condition is given. Besides, according to UIC Code, formation layer thickness has been shown by table depending on the different types of soil quality class. Types of slab track systems used worldwide and their cross-section properties are also briefly shown together with figures of cross section properties. Some of these balastless tracks have been examined more detailed and their advantages are introduced in general. Lots of different balasstless track systems have been classified in a table and the advantages of ballastless track systems are given in general. In the 3rd chapter, the components of the cast in-situ slab track system which are rail, fasteners, sleepers and concrete plate or plinth beams are examined and the components of these in worldwide use are classified and introduced. Rail types are described as flange rail, double headed rail and Vignol rail. Technical properties of the rail types briefly given and the specification, features that they should have and information about pros and cons of these elements explained. Rail fasteners systems are described as two types, rigid system fasteners and elastic system fasteners. The features of these types of fasteners are shown together with figures. After that sleepers defined under the titles of wooden, steel, concrete and plastic sleepers. Some types of the sleepers that tried and currently being used in the world explained. In concrete sleeper title, post-stressed and pre-stressed concrete sleepers have been described. In this chapter we also give some information about plinth concrete beam and explain the measures must be taken during its construction stage briefly. In the 4th chapter, a type of slab track systems LVT has been chosen and explained in more detail. Here we also mentioned about ground born noise and vibration mitigation which has an inspiration to choosing LVT slab track. Some measures that should be taken for special buildings such as hospital and theater are given. Besides this, LVT systems features and advantages are explained. In 5th chapter, design of railway superstructure with an example of LVT system has been explained. At first, we explain how the wheel loads are transferred from top (rail) to sub-base showing modeling of railway superstructure in figure. Slab track modeling has springs between the layers that form the superstructure. From bottom to top, first springs take place under the rigid concrete slab which represents the soil elasticity. Since we examined LVT system here, second spring is between rigid slab and LVT concrete block so called block pad as explained in chapter 4 and the third spring for modeling takes place under the rail representing rail pad stiffness. This type of modeling can also be seen in figure. In chapter 5 we also introduce the forces which effect railway superstructure. Forces studied under the titles of vertical forces, horizontal forces, temperature stresses and other forces and technical information about these forces are given. Vertical forces investigated under two titles, static and dynamic vertical forces. As for the horizontal forces, they are shown under two titles either as the forces acting parallel to longitudinally direction of railway superstructure and forces acting perpendicular direction to the railway. In temperature stresses section, the calculation of forces emanating from temperature has been given by equation depending on unit length change and temperature change. Railway roadway design is performed assuming that railway is a beam laid on elastic platform, and therefore, determination of soil type and coefficient of soil stiffness or soil spring value is important. Here in chapter 5, we give information about calculation of coefficient of soil stiffness in light of Winkler and Zimmermann’s equations. For obtain one soil coefficient of stiffness when multi-layer case is subject, Eisenmann’s equivalent layers theory has been used and introduced by the help of a figure and the calculation of this method has been explained. Another coefficient used for superstructure static analyses is dynamic impact factor. Today many types of calculation method developed for taking into consideration of the impact of dynamic forces acting on railway. In this study we used Eisenmann’s equations for the speed until 200 km/h. 5th chapter also explain the analyses and concrete slab design calculation for LVT system under different vehicle loads. The loads chosen here have been taken from UIC and EN1991 standards. For freight train maximum speed taken as 100 km/h. As for the passenger train and high-speed train maximum speed taken as 120 km/h and 250 km/h respectively. Load Model 71 from UIC is used for freight train. For passenger and high speed train, type-2 and type-3 load model from EN 1991 has been used. It should be kept in mind that there is much more different type of load models depending on vehicle style. For analysis, FEA base computer program SAP2000 has been preferred. This program allows engineers to model almost every type of structure realistically. To model LVT system in the program, modeling technique of which illustration is given by figure in chapter 5 has been used. Rail pad which take place under the rails at joints and rubber boot and LVT block pad represented by springs. Here LVT concrete block pad and the rubber boot which contains the block thought together and their stiffness combined calculating an equivalent spring coefficient. Soil condition considered as good and class of the subbase soil taken as QS3 according to soil classification of UIC Code. In the model soil represented with springs either. Slab area that considered here a bearing beam laid on elastic platform divided into small finite elements for analysis. The analysis results are shown in figures as contours diagram and concrete design has been performed using the longitudinally and transverse moment values. There might be lots of soil types and geometrical properties on the route of railway track. Thus, quite a lot different conditions may be needed to take into account. In this study the chosen part is regarded as an alignment and calculation is performed accordingly. In final section we explained our assessments and thoughts about the results of the study.