Abstract
To study the mechanical properties of the China Railway Track System type II (CRTS-II) ballastless slab track structure, a 1/4-scale specimen of a CRTS-II slab ballastless track-32-m standard prefabricated simply supported box girder bridge with three spans and two high-speed railway lines was developed. The mechanical properties of the structure under the action of daily natural temperatures were studied under the natural environmental conditions. The structural strain and relative interlayer displacements were analyzed. The results show that the temperature of the CRTS-II ballastless track-bridge structural system changes periodically every 24 h. The strain of the structural layers of the track system first increases and then decreases sinusoidally, and the internal strain of the track system lags along the vertical depth direction. The relative displacement between the layers of the ballastless track bridge structure system increases with the increase in temperature. The extreme value of the vertical relative displacement appears between the track bed and the bridge at section 1/4 in the span, so it should be paid attention to by the maintenance personnel. Due to the constraint of the shear slots, the structural strain and relative displacement at the fixed end near the shear slots are smaller than those at the sliding end. The mid-span deflection is the largest, and the overall deflection during the cooling phase is more significant than that during the heating phase.
Highlights
With its advantages, such as high smoothness, high stability and good durability, the China Railway Track System type II (CRTS-II) ballastless slab track has been widely used in China [1,2,3]
It can be seen from the figure that at 19:00, the longitudinal relative displacement of the track slab and the base plate is relatively large
(1) The temperature of each structural layer of the track system changes with the change in the ambient temperature, showing a sine curve periodic change rule of increasing first and decreasing; because of the poor thermal conductivity of the material, the temperature change in the track system lags behind the change in the ambient temperature, and the lag feature is more obvious with the increase in the depth from the top of the track slab
Summary
With its advantages, such as high smoothness, high stability and good durability, the CRTS-II ballastless slab track has been widely used in China [1,2,3]. Dai Gonglian [17,18,19] et al embedded temperature sensors in ballastless tracks on curved bridges, performed long-term monitoring of the temperature field, and obtained the time-dependent temperature field law of longitudinally connected ballastless slab track-bridge systems under various natural conditions, such as extreme summer and cold winter temperatures, as well as the vertical and horizontal temperature gradient load modes. Liu Fushan [20] established a three-dimensional finite element analysis model of the CRTS-II ballastless track temperature field and studied the time-dependent law and the influence of various factors on the temperature field of ballastless tracks. A 1/4-scale model of the CRTS-II slab ballastless track-32-m standard prefabricated supported box girder bridge with three spans and rail and fasteners were constructed simulating the natural environment without direct sunlight in extreme summer conditions, and the mechanical performance of the CRTS-II ballastless track system under daily temperature action was studied. The experimental basis is provided for further research on the temperature field, mechanical properties and temperature damage of the structure under the action of temperature
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