Experimental study on CRTS Ⅱ ballastless track-bridge structural system mechanical fatigue performance

Abstract

With the large-scale application of high-speed railways (HSR) in China, the ballastless track-bridge will inevitably experience fatigue damage. As a result, the maintenance and repair of the HSR track-bridge are becoming extremely urgent. However, the research on the track-bridge is very lacking presently and its mechanical fatigue performance and service life are still uncertain. Therefore, it is of great necessity to carry out a fatigue test on track-bridge to reveal the mechanical properties evolution of the structure and predict its service life under fatigue train loads. In this paper, a quarter-scale specimen of a prestressed simply supported concrete box-beam with CRTS Ⅱ (The China Railway Track System Type Ⅱ) ballastless track was constructed. A series of fatigue tests were carried out on the structural system and the following conclusions were noted. First, there are no visible cracks on the surface of the track-bridge after a fatigue loading test of 18 million cycles, and its mechanical properties of collaborative work perform well. Second, the mechanical performance of the box-beam remain elastic and its stiffness is basically stable under the long-term fatigue train load. Third, the calculated fatigue life of the track-bridge shows that the box-beam, track slab, base slab and cement asphalt mortar (CA mortar) all had extremely long fatigue lives, which demonstrates that it is difficult for them to suffer failure under fatigue train loads. Moreover, after the fatigue test, the results of cumulative fatigue damage show that the most damaged component of the track-bridge is the box-beam, followed by the CA mortar, the base slab and the track slab, and their predicted residual life are expected to be 73.67%, 92.90%, 99.99% and 99.99% of the total fatigue life, respectively. Therefore, more attention should be paid to the damage of box-beam in the repair and maintenance of the HSR track-bridge.