A multifaced analysis of railway sleepers and scrutinize of different railway sleepers on an example line

It is an inevitable necessity to have reliable and efficient means of transportation due to rapidly increasing population and consumption both in our country and the world in general. Those researches that compared transportation means, based on the data of proportion between the energy spent and the quantity of passengers and the cargo transported continuously highlight the railways as the main way of transportation that will meet this increasing need for reliable and efficient transportation. Railways are integral to the transportation system of many countries around the world. Consequently, it is necessary from the safety and economic perspectives that they maintain their design geometry over their lifespan, with minimal interruption to day to day operations for maintenance. However, with the passage of traffic over a prolonged period, sections of a railway track inevitably deteriorate, leading to speed restrictions and poor levels of passenger comfort. Understanding railway track behaviour is of importance to gain insight into the complex mechanisms that lead to track deterioration especially as a railway track comprises of several interdependent components. It remains important to policy makers, rail practitioners and researchers to identify new techniques, innovations or processes that will prolong intervals between scheduled track maintenance to provide a sustained degree of passenger comfort and maintain the economic activity that rail transport yields. In fact, new railways are being constructed and the existing railways are being repaied to meet the increasing need of economical and convenient transportation. Railway sleeper, which mainly functions as both transmitting the load of trains from rails to ballasts and to the ground and stabilizing the railway track geometry, will be regarded as one of the main components of railway line structure. There are different types of railway sleepers that are used throughout the railway construction history and consequently, railway sleeper technology is still improving. The main aim of the present study is to review the extensive literature of different kinds of railway sleepers. This review of the literature will include those fundamental railway sleepers that had been used from past to present both in Türkiye and throughout the world, those railway sleepers that are under development and testing stages, and those railway sleepers which are developed for particular special needs. The information about the production methods of excessively used wooden, steel and reinforced concrete railway sleepers are also included in the review of literature. Excessive use of wooden and steel railway sleepers in the railway lines is decreasing nowadays due to increasing speed of railway operation speeds, axle loads and comfort needs. In the meantime, the use of reinforced concrete railway sleepers is increasing depending on the rapid improvements in the reinforcement concrete technology and the increases in the global competition conditions. As a matter of fact, special characters of reinforced concrete railway sleepers are underlined more throughout this study over the other two types of railway sleepers. Besides the fact that the usage of reinforced concrete sleepers are increasing in general, particularly the usage of pre-stressed B70 type of monoblock reinforced concrete sleepers in the national conventional and high speed train lines are also increased. This fact gave the pave for reviewing those sleepers specifically in the present study; namely their technical features, production standards, quality and design approvals and tests. Even though the operational speed and maximum axle load is lower for B70 type, B58 type of monoblock reinforced concrete sleepers are still used in TCDD railway lines; therefore information about B58 type of monoblock reinforced concrete sleepers is also included in the study. In order to delve into the fundamental production essentials on monoblock reinforced concrete slepeers, production of monoblock sleepers' by carousel methods, the present researcher visited one of the private institutions' factory located in Afyon, Turkiye. The factory, which the researcher had visited, mainly produces pre-stressed B70 Type of monoblock reinforced concrete railway sleepers and produced the Ankara-Konya Speed Train railway slepeers. After reviewing the primary production essentials of sleepers in the study, both the advantages and disadvantages wooden, steel and reinforced concrete sleepers' are compared with each other through using the relevant experiences and literature. The three types of railway sleepers are compared with each other by using four categories; namely, average usage life span, commonly usage tracks, supply and construction costs and environmental impact. It is believed that, the data reviewed by comparing between the sleepers in this section would help the reader of this research understand the exceeding usage of reinforced concrete sleepers' over the other two types sleepers. The distribution of the loading under the railway sleeper has a particular impact on the designing processes; consequently, the simplified explanation on these distributions is included in the preceding chapter. Special attention is also given to critical points of designing essentials of sleepers that are determined by the leading authority on railways, namely UIC (International Union of Railways) Understanding railway track behaviour is of importance to gain insight into the complex mechanisms that lead to track deterioration especially as a railway track comprises of several interdependent components. It remains important to policy makers, rail practitioners and researchers to identify new techniques, innovations or processes that will prolong intervals between scheduled track maintenance so as to provide a sustained degree of passenger comfort and maintain the economic activity that rail transport yields. In the final section of the research, Marmaray BC1 Project, which has a particular importance on İstanbul's and Turkiye's transportation system, is investigated in order to illustrate the usage areas of railway sleepers and to examine the selection of the sleeper type. The factors that are influential in selecting the appropriate sleeper, usage areas and differences between the sleepers both in costing and in usage are discussed with a special attention given to this particular project. The discussion of the Marmaray BC1 Project helped the researcher to identify the importance of railway sleepers as an element on the estimation of the upper construction component of railway lines, and to consider the effects of the selection of the appropriate railway sleeper to the comfort and construction costs of railways. Additionally, the researcher used a hypothetical one-kilometer railway line to simplify the probable construction costing calculation for a better understanding at the end of the research.