Experimental and numerical studies of longitudinal crack control for pre-stressed concrete sleepers

In the network of Iranian railways, pre-stressed concrete sleepers are more popular than the other types due to their high performance. One of the defects observed in these sleepers is longitudinal cracks caused by irregular and excessive pressure before and during the track operation. These cracks usually initiate from the rawlplug locations and propagate to the middle or even to the whole lengths of the sleeper. This excessive and additional pressure in rawlplug positions are due to the water freezing, existence of rock fines or fine aggregates in the fastening holes, deformation of the rawlplug or a combination this effects. This paper presents a test methodology named as Katrak test to exhibit failure planes in non-strengthened and strengthened (transversely reinforced) sleepers. In this study, the effects of the extra pressure in rawlplug positions are simulated by applying cylindrical pressure inside the rawlplug holes using a physical and numerical (FEM) models. The results show that the Katrak test and simulation performed could be an appropriate method for studying sleeper behaviour and formation of longitudinal cracks under excessive pressure.