Analytical study on longitudinal crack control for B70 mono-block pre-stressed concrete sleepers

• In this research, creation of longitudinal cracks before track operation has been studied.
• A sensitivity analysis of the tensile stress in the rawlplugs positions was carried out against changes in the pre-stressing force.
• The cylindrical pressure inside the rawlplug holes increases the tensile stresses around the holes and eventually leads to extension of longitudinal cracks.
• High values of pre-stressing force can be a main factor in creating longitudinal cracks.

The B70 mono-block pre-stressed concrete sleeper is one of the most widely used types of concrete sleepers for railways. One of the most important defects of this type of sleepers is longitudinal cracks both before and during railway track operation, which usually begins at the rawlplugs positions and continues up to the central and regional area of the sleeper. In this research, creation of longitudinal cracks before track operation has been studied. For this purpose, effects of exerted applied loads on the sleeper including pre-stressed loading and cylindrical pressure loading in the circular hole of rawlplugs positions (four different types) in creating longitudinal cracks were investigated using the ABAQUS Finite Element software. In addition, a sensitivity analysis of the tensile stress in the rawlplugs positions of the B70 pre-stressed concrete sleeper was carried out against changes in the pre-stressing force as one of the most important parameters in the structural design of this type of sleeper. According to the research results, the cylindrical pressure inside the rawlplug holes increases the tensile stresses around the holes and eventually leads to extension of longitudinal cracks. Furthermore, the implementation of loadings on the B70 mono-block pre-stressed concrete sleeper increases the intensity of the damage significantly. The numerical model also shows the linear behaviour of the changes in the pre-stressing force and, as a result, high values of pre-stressing force can be a main factor in creating longitudinal cracks.