Evaluating the Structural Behavior of Turnout Sleepers in the Case of Raising Speed

In this research, the mechanical behavior of both timber and concrete sleepers in a standard turnout is evaluated with consideration of speed effects. In approaching this evaluation, current practices in the structural analysis of sleepers are surveyed and then, the sensitivity analyses with ABAQUS software are made based on governing criteria (i.e. bending and shear stresses as well as stress distribution under sleeper). Considering various sleepers with different dimensions in a turnout, two specific ones are selected as the representatives of moving (switch) and fixed (frog) parts. The results show that the maximum bending stress of timber sleeper compared to the concrete one is reduced to about 55%, due to more flexibility. However, better behavior is resulted in concrete sleeper because of higher strength of materials. Meanwhile, the bearing pressure of timber sleeper on ballast layer is about 80% higher which means that, the concrete sleeper provides better stress distribution for ballast materials. The theoretical effects of speed increase from 150 to 300 Km/hr is also investigated which leads to an increase of about 30% in the stresses outputs