Field Investigation on Dynamics of Railway Track Pre-Stressed Concrete Sleepers

Abstract

A comprehensive field investigation was made with the aim of achieving a better understanding of the dynamics of railway track pre-stressed concrete sleepers. Modal analysis and free decay method were used to determine the natural frequencies, model shapes and damping of sleepers. The validity of the results is discussed by comparing the results obtained here with those available in the literature. In order to investigate the characteristics of the dynamics of the loads imposed on the sleepers, load cells were installed between the rail seat and the sleeper and beneath the sleeper, recording the interaction between both sleeper and rail, and sleeper and ballast. The loads transferred from the rail to the sleeper and from the sleeper to the ballast were measured as a function of train speed. The rail seat load and the contact pressure between the ballast and the sleepers versus train axle loads and train speeds were recorded. The effects of the sleeper supporting conditions on the sleeper dynamic behaviour were investigated. The ratios of the rail seat load and the ballast contact pressure to the wheel load were obtained from the analyses of the field test results. These ratios were used to calculate the dynamic impact factors and ballast-sleeper pressure distribution patterns required for the design of sleepers. The methods, the test procedures and the results are presented and discussed in this paper.

New Advances in Design of Railway Track System

“…Therefore, the use of the AREMA recommendation (Table 1) for dynamic impact factor is suggested for heavy haul railway with the train speed less than 80 km/h. On the other hand, the use of mathematical expression proposed by ORE (indicated in Table 1) is more justifiable for the calculation of dynamic impact factor in high speed railway tracks [31]. The effects of the dynamic characteristics of the load on the sleeper and the ballast (Rail-seat load and ballast-sleeper contact pressure) have been recently investigated by Sadeghi and his colleagues [31].…”

“…On the other hand, the use of mathematical expression proposed by ORE (indicated in Table 1) is more justifiable for the calculation of dynamic impact factor in high speed railway tracks [31]. The effects of the dynamic characteristics of the load on the sleeper and the ballast (Rail-seat load and ballast-sleeper contact pressure) have been recently investigated by Sadeghi and his colleagues [31]. They indicated that the dynamic characteristics of the load have more impact on the amount of ballast-sleeper pressure at the points which experience less pressure.…”

“…That is, the less pressure, the more influence due to the load dynamics. Since with an increase in load speed the pressure in the middle and cantilever parts of the sleeper considerably increases, we are led to believe that the load distribution under the sleeper will become increasingly uniform with increasing load speeds [31]. This means that the assumption of a uniform pressure distribution under the sleeper for train speeds of more than 120 km/h is justifiable [31].…”

“…The vertical axis in this figure is the dynamic coefficient factor or dynamic impact factor. Since the DIF calculated in figure 14 is based on the effects of dynamic load on sleeper loading patter, implementation of this figure in the design of sleepers and ballast is more justifiable and lead to a better accuracy [31]. …”

Experimental and Numerical Analyses of the Failure of Prestressed Concrete Railway Sleepers

“…Recently, the need for sleepers' replacement in old railroads has been increasing, as well as the average increase of the speed guide provided by increasingly modern trains, which economically justifies the large amount of studies on this theme around the world [5,12,13].The sleepers are subjected to cyclic loads during their whole life; the materials that comprise them are subjected to an intense process of fatigue. It is desirable that the sleeper is free of cracks under dynamic loading, because if cracks occur, there is a great increase in stresses in the prestressing reinforcement and an increase of up to 50% in the transfer length [14][15][16]. Therefore, designing a prestressed sleeper is a good solution to avoid problems with simple concrete [1,15,17,18].Thus, this paper aims to evaluate the mechanical behavior of prestressed concrete sleepers, in accordance with the Brazilian and American standards and the common pathologies they are submitted to over their design life.…”