Fatigue of steel-fibre-reinforced concrete prestressed railway sleepers

Prestressed concrete sleepers are one of the major components in any railway track system that distributes wheel loads from the rails to the underlying ballast bed. Concrete sleepers are usually designed with an expected life of 50 years. However, during their life span, sleepers may experience extreme loading conditions from infrequent but high-magnitude wheel loads produced by a small percentage of “bad” wheels or rail abnormalities. These loads can initiate cracking in the sleepers that reduces durability and increases the risk of fatigue failure of prestressing strands through undergoing millions of cyclic loads. The physical performances of the concrete sleeper such as durability, energy absorption, fatigue and toughness can be improved with the inclusion of steel fibres. This study investigates the efficiency of using steel fibres to improve load carrying capacity and fatigue performance of rail sleepers. Eight prestressed concrete sleepers were tested with fibre contents of zero, 0.25% or 0.5%, by volume, under constant amplitude cyclic and static loading. The sleepers with 0.5% fibres demonstrated higher static capacity and extended fatigue life, lower deflections and finer crack widths than that of sleepers without fibres. The sleepers with 0.25% (20 kg/m3) fibres showed variable results and, in some cases, a reduced fatigue performance. It is demonstrated that a minimum volume of fibres is essential to ensure enhanced performance.