Steel Sleeper Performance

In-track measurements of wheel loads and sleeper strains, and laboratory measurements of fatigue life have been used to develop a model that was intended to predict the fatigue life in track of M7.5 non-insulated TRAK-LOK 2 steel sleepers under a range of track and freight conditions. The model is empirically based on data from sites that had (i) traffic with nominal maximum axle load of 15-20 tonnes, (ii) gauge of 1067mm, and (iii) no interspersed sleepers. The amount of in-track variability is such that the model is not sufficiently accurate to be a practical tool for steel sleeper design. An alternative design method is to use laboratory fatigue tests, but this is subject to even greater uncertainty, as current laboratory tests do not consistently reproduce in-track strains.