Reducing the cost of prestressed concrete railway sleepers

Abstract

In Sri Lanka, the cheapest and safest mode of transportation is railways. The loads applied by trains are transferred to the ground through rails supported on railway sleepers. In Sri Lanka, among the two types of sleepers in use, the prestressed concrete sleepers are the most common. The use of prestressed concrete sleepers has increased the structuralstiffness andprecludedseveralproblems that are associatedwith wooden sleepers. However, prestressedconcrete sleepers are comparatively heavy and expensive. Therefore much ongoing research is directed towards reducing the self-weight and the cost. This paper describes thefindings ofa study on Sri Lankan prestressed concrete railway sleepers. Cross section, amount ofprestressing steel and the amount of ballast required are the main variables, while ensuring adequate capacityfor both positive and negative moments at midspan and railseat sections. Sleepers produced at Ekala SECprecast yard and three new alternative sleeper options with different dimensions were selectedfor comparison. The three sleeper options were selected considering the required section moduli and the present steel moulds available for casting. The calculations were done in accordance with AS 1085:14-2003. It wasfound that the number of tendonsfor Ekala sleepers can be reduced to 14 nos. with grade 50 concrete, and it can befurther reduced to "■ 12 nos. with increased grade ofconcrete. Axle load capacity can be increased to 22 tonnesfor Ekala sleepers with 14 nos. oftendons andwith grade 60 concrete. Option 1, which is the lightest sleeper among the sleepers considered, has 16 nos. oftendons and gives the least overall cost. It is recommended to cast and testsamples ofthis Option 1 sleepersto confirm theirperformance before using them in the tracks.