POLYMERIC COMPOSITE RAILWAY SLEEPERS

1 2. Uluslar aras Rayl Sistemler M hendisli i Sempozyumu (ISERSE 13), 9-11 Ekim 2013, Karab k, T rkiye POLYMERIC COMPOSITE RAILWAY SLEEPERS Amir GHORBAN a, Se kin ERDEN a, * a, * Ege University, Mechanical Engineering Department, Izmir, Turkey, a Ege University, Mechanical Engineering Department, Izmir, Turkey, zet Demiryolu traversleri, demiryolu sisteminin en nemli elemanlar ndand r. Ah ap traversler hala en yayg n malzeme say lsa da, beton ve elik malzemelerin kullan m da artmaktad r. Ayr ca, geri d n t r lebilir malzemelerden retilen traversler de son zamanlarda ilgi ekmektedir. Plastik at klar n geri d n t r lmesiyle hem evre temizli i, hem de para tasarrufu hedeflenmektedir. Kompozit traversler sa lam, dayan kl ve g venilir oldu undan, yayg n traverslere g re daha az bak m gerektirir ve daha uzun m rl d r. Bu nedenle, d k maliyetli ve uzun vadeli bir z m olarak g r lebilirler. Bu al ma, alternatif bir demiryolu travers malzemesi olan polimerik kompozitlerle ilgili son geli meleri g zden ge irmektedir.

2 Yenilik i kompozit traversler zerine y r t len ara t rma ve geli tirme faaliyetleri sunularak avantaj ve dezavantajlar s ralanm t r. Anahtar kelimeler: Polimerik kompozit malzeme, Demiryolu traversleri. Abstract RAILWAY SLEEPERS are one of the most important elements of the RAILWAY track system. Although timber SLEEPERS are still the most common, use of pre-stressed concrete and steel materials is also increasing. In addition, ties produced using recycled materials are of interest, recently. By recycling plastic waste, considerable amount of money can be kept from ending up in the landfills. As COMPOSITE ties are strong, durable, and reliable, they require less maintenance and have longer life than common railroad ties. Therefore, they can be an excellent, cost-effective and long-term solution. This paper presents a review of recent developments on polymer composites as an alternative material for RAILWAY SLEEPERS . An overview of on-going research and development on innovative fiber COMPOSITE RAILWAY SLEEPERS with investigation on their advantages and disadvantages are also presented.

3 Keywords: POLYMERIC COMPOSITE material, RAILWAY SLEEPERS . 1. Introduction RAILWAY SLEEPERS are one of the most important elements of the RAILWAY track system. They are the beams/ties laid underneath the rails to support the track[1]. Their function is to transfer the loads to the ballast, transversely secure the rails to maintain the correct gauge-width and to resist the cutting and abrading actions of the bearing plates and the ballast material [2]. SLEEPERS also resist the lateral and the longitudinal movement of the rail system. Different kinds of materials are used in sleeper production. Hardwood timber is the most widely used sleeper material. There are more than billion timber SLEEPERS installed in the RAILWAY track throughout the world [3]. In order to have a reliable track system and maintaining the quality of the track system to a specified service level and ensuring. The safe track operation, a wide range of ingredients should simultaneously be considered.

4 Strength and durability of the SLEEPERS is one of those ingredients that play an important rule in track system. Beside wood, concrete and steel were widely applied in SLEEPERS but recently the use of POLYMERIC - COMPOSITE , because of their remarkable properties was also increased. This paper presents an overview of advantages and disadvantages of the aforementioned materials and also introducing the POLYMERIC COMPOSITE as an alternative material for RAILWAY SLEEPERS . Ghorbani A., Erden S. 2. Sleeper Materials Sleeper materials currently in use and researched as potential alternatives are grouped here as non- POLYMERIC and POLYMERIC SLEEPERS , which are also sub-grouped to give additional information. Non- POLYMERIC SLEEPERS There has already been a vast research and development effort into materials for SLEEPERS since railways were introduced. Timber SLEEPERS are still the most common, however, use of pre-stressed concrete and steel SLEEPERS is also increasing.

5 The advantages and disadvantages of these RAILWAY materials will be discussed in the following sections. Additionally, a comparison of their properties is given in tabular form (Table 1). Timbers Timber SLEEPERS have been widely used during recent decades. Like the others, it has advantageous and disadvantageous. The main advantage of the timber is their adaptability as it can be fitted with all types RAILWAY track. On the other hand while the cost of their maintenance is low in comparison to the other kinds, its application seems to be a little bit more alternative [3]. Fungal decay and splitting at the ends of the timbers are the most common types of sleeper failures. The first one mostly refers to the environmental situation [4] and the second one refers to the very large transverse shear loading exerted to the SLEEPERS [5]. Softwood timbers Softwood is wood from gymnosperm trees such as conifers, evergreen trees are often called softwoods.

6 Softwood timber does not offer the resistance of hardwood sleeper to gauge spreading and spike hole enlargement [6]. In addition, softwood SLEEPERS are not as effective in transmitting the loads to the ballast as the hardwood SLEEPERS do, thus they should not be mixed with hardwood SLEEPERS on the RAILWAY track. Concrete Concrete, because of its natural weakness in tension is not used in sleeper s products. Pre-stressed concrete is a method for overcoming this matter. It can be used to produce beams, floors and bridges with longer span. In this case the mentioned method is applied in timbers production by concrete. Pre-stressed concrete SLEEPERS have become widely and successfully accepted for RAILWAY sleeper usage especially in high speed lines. Their economic and technical advantages are the results of longer life cycles and lower maintenance costs. With their great weight, concrete SLEEPERS assure optimal position permanence and stability even for traffic at high speeds.

7 In fact, many pre-stressed concrete sleeper technologies have now been developed. Mono-bloc and twin-bloc pre-stressed concrete SLEEPERS are most commonly use concrete SLEEPERS . Twin-bloc, because of its less weight could attract more attention. Twin-bloc sleeper is made up of two concrete parts supported by steel reinforcements. Although, it has a prominent disadvantageous as it has tendency to twist when lifted which makes it difficult to handle an install these kinds of SLEEPERS . Concrete SLEEPERS , beside their advantageous like more life-time and strength, have some disadvantageous too. Such these disadvantageous are their heavy weight which required specialized machinery during laying and installation and also their production casts, while their initial cost is almost double that of hardwood timber SLEEPERS . The investigation to the timber and concrete SLEEPERS , reveal that the concrete SLEEPERS higher SLEEPERS have high stiffness characteristics and the design requires higher depth than the existing timber SLEEPERS .

8 Steel Australia has developed a world reputation in technology related to the design and performance of steel RAILWAY SLEEPERS . Ghorbani A., Erden S. The Institute of RAILWAY Technology at Monash University is working to minimize cost and ensure superior performance of steel SLEEPERS [7]. Currently, steel SLEEPERS account for over 13% of the RAILWAY SLEEPERS used within Australia. Steel SLEEPERS can be interspersed with the existing track but in a fixed interspersing pattern to reduce the variation in the track geometry and prevent the early in-service failure of SLEEPERS . A steel sleeper weighs less than timber sleeper which makes it easy to handle as well as having a life expectancy known to be in excess of 50 years. However, steel SLEEPERS are being used only on more lightly travelled tracks and are regarded as suitable only where speeds are 160 km/h or less [8]. Steel SLEEPERS require extra care during installation and tamping due to their inverted through profile which makes them difficult to satisfactorily pack with ballast.

9 Observations of rail deflections under imposed vehicle track loading have shown that the steel SLEEPERS settle a greater amount than the timber SLEEPERS , indicating that the steel and adjacent timber SLEEPERS are not carrying an even proportion of the imposed wheel loading [9]. Furthermore, steel SLEEPERS are expensive and are used only in minimal number because of the fear of corrosion. Another problem with steel SLEEPERS is fatigue cracking in the fastening holes caused by moving trains [10]. Table 1. Comparison of current materials for RAILWAY SLEEPERS [11] Properties Hardwood Softwood Concrete Steel Adaptability Easy Difficult Difficult Difficult Workability Easy Easy Difficult Difficult Handling and installation Easy Easy Difficult Difficult Durability Low Low High Low Maintenance High High Low High Replacement Easy Easy Difficult Difficult Availability Low High High High Cost High Low Very high Very high Fasteners Good Poor Very good Poor Tie ballast interaction Very good Good Very good Poor Electric conductivity Low Low High Very high Impact High High Low Medium Weight (kg) 60-70 60-70 285 70-80 Service life (years) 20-30 20 60 50 POLYMERIC COMPOSITE SLEEPERS Recent developments in fiber composites now suggest their use as alternative material for RAILWAY SLEEPERS .

10 These developments can be subdivided into new RAILWAY SLEEPERS produced by combining other materials with fiber composites and the strengthening of existing sleeper materials with fiber COMPOSITE wraps. One of the earliest COMPOSITE sleeper technologies developed in Australia is made of polymer concrete and glass fiber reinforcement (Figure 1) that was used as replacement for timber, steel and concrete SLEEPERS . Figure 1. Glass fiber reinforced polymer concrete sleeper weighing 61 kg [11]. Ghorbani A., Erden S. Glue-laminated fiber COMPOSITE sandwiches COMPOSITE sandwich structure made up of glass fiber COMPOSITE skins and modified phenolic core material [12]. The results suggest that the glue-laminated COMPOSITE sandwich beams have the strength and the stiffness suitable for turnout sleeper. In glue-laminated sandwich beams, it was found that the fiber wraps had minimal effect on the bending stiffness and strength but has a more pronounced effect on the shear strength, Wich an almost 7% higher strength for specimen with wraps than their unwrapped counterpart.