Performance of the centre section of broad gage prestressed concrete sleepers under fatigue loading and controlled cracking

摘要

Prestressed concrete sleepers have been widely used in railway tracks for some decades with excellent performance. The traditional design rule for prestressed concrete sleepers has been based on limiting the long-term tensile stress at the most loaded point of the cross section to avoid cracking. In broad gage tracks, the centre section is subjected to higher bending moment than the rail seat section. Controlled cracking has been allowed at the centre section by recent design guidelines (prEN 13230-6) but fatigue and durability issues may arise under such situation. In addition, it is realistic that single events like overloads or dynamic effects may lead to cracking. Therefore, the performance of the centre section under controlled cracking situation should be studied, with emphasis on fatigue and residual cracks. The present paper presents an experimental campaign and a theoretical analysis on prestressed concrete sleepers subjected to severe fatigue loading at the centre section. According to the results, it can be concluded that the fatigue performance of studied sleepers is rather satisfactory. Moreover, the study has also focused on the evolution of the residual crack width and it is shown that residual cracks remain smaller than 0.05mm for bending moments significantly larger than the characteristic bending moment.