Experimental and Numerical Studies of Longitudinal Crack Control of Prestressed Concrete Sleeper

In Iran railway network, prestressed concrete sleepers are more popular than other types, due to their more resistance and other advantages. One of the defects observed in this type of sleepers, is longitudinal cracking, before and during operations that usually start from roll plaque and continues to the middle of the sleepers. These cracks may be formed due to excess pressure within the roll plaque of sleepers, water freezing inside roll plaque, existence of fine aggregates when closing the bolt of roll plaque, distortion and lack of standard bolt or roll plaque or other destructive factors. In this paper, approximation and modeling of the effects of mentioned factors by cylindrical pressure in place of roll plaque holes are presented. Numerical studies with minimal changes in geometry of monoblock prestressed concrete sleepers B70 and by the hole of location and roll plaque reinforcement modeling were done and the relation between unwanted additional stresses inside the roll plaque with concrete were investigated. By cylindrical pressure in place of roll plaque and increasing it to concrete failure, impact of this pressure in place of roll plaque is presented analytically and experimentally. The results show that unwanted stress in place of roll plaque increases the cross tension stress, due to cracking. In the next step, by considering the path and distribution of cracks and strengthening transverse reinforcements, transverse tension stress in various patterns of strengthened and non strengthened sleepers, is investigated. The results show that use of transverse reinforcement can control cracks and reduce the tension stress around holes of the roll plaque.