Abstract
The cast-in-place concrete base plate is a main member of the China Railway Track System (CRTS) III ballastless track structure that is prone to generating early transverse cracking. Such cracks can dramatically affect the performance and service life of the railway track structure. This study investigated the influence of temperature and moisture boundary conditions on early cracking behavior of the CRTS III base plate by using approaches of both in situ measurements and numerical modelling. In-site measurements of strain and temperature were made in four test series of CRTS III base plates under the same natural environmental condition but cured with different regimes, and a total of 96 measuring positions were monitored for up to 150 days. The results showed that the strain magnitude and distribution in the field base plate, the initial time at cracking, and the observed cracking pattern varied significantly between the different test series. In order to understand the mechanisms that create these transverse cracks and to provide guidelines for the current curing strategy during construction, the characteristics of temperature-induced and moisture-induced stresses were analyzed by using 3D numerical modelling and by considering early-age concrete creep properties, meteorological factors, and the influence from environmental boundary conditions. The calculated results revealed that early-age transverse cracking in CRTS III base plate depends more on drying shrinkage stress than temperature stress. By conducting this study, we expect to provide guidance for reducing or eliminating early cracks of CRTS III concrete base plate.
Highlights
Due to high reliability and stability, ballastless slab track systems have been widely utilized in high-speed railways all over the world
The current study focuses onfocuses the baseonplate resting on resting on -supported girder bridges, which utilized are a widely utilized -supported prestressed prestressed girder bridges, which are a widely structure form because bridge foundations make up a great percentage of foundations offoundations the highspeed structure form because bridge foundations make up a great percentage of of railways in China
Since it is well known that a large part of temperature gradient in concrete plate is nonlinear and can cause large inner stress within the concrete, this section focuses on the statistical distribution of temperature gradient in field base plates cured with different regimes
Summary
Due to high reliability and stability, ballastless slab track systems have been widely utilized in high-speed railways all over the world. The steam-cured concrete precast slab, the self-compacting concrete (SCC) filling layer, the isolation layer (geotextile material), and the concrete base plates are the main components of the CRTS III slab track, which is a laminated structure. According to field investigations [2,3], transverse base plate cracking is one of the major forms of slab track defects. These cracks are located on the surface and at the middle portion of the base plate, and a few of them are extended to full depth. The field crack surveys conducted at the Beijing–Tangshan High-speed Railway revealed that most transverse cracks were initiated within a month after a specified 14-day wet-curing period. After about 2 months of casting, up to 50% cracking probability was reported
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