# Calculation of Reasonable Tension Value for Longitudinal Connecting Reinforcement of CRTSII
## 1 Introduction  
The ballastless track is suitable for high-speed railways because it provides great smoothness and stability for the railway line, and has the advantages of high structural stability, good stiffness uniformity, long service life, and little maintenance work compared with the conventional ballast-track [1, 2]. Figure 1 shows the CRTSII slab track and its components. The primary components of the slab track system are the rails, rail pads, track slab, cement-emulsified asphalt (CA) mortar layer, and concrete base. The CRTSII slab ballastless track is connected longitudinally between track slabs by tensioning the longitudinal connecting reinforcement between track slabs, and casting wide and narrow joint concrete [3]. The tensioning of longitudinal reinforcement plays a role in ensuring the longitudinal connection reliability of the ballastless track and limiting the crack width at wide and narrow joints. According to the original design concept [4], the tensioning of longitudinal reinforcement generates 300 kN of pre-pressure, which can effectively reduce the crack width and the stress of the connectingreinforcement on wide and narrow joint concrete. The wide and narrow joint is an important link in the longitudinal system of the CRTSII slab ballastless track. Although the slab track has gained successful improvements and applications in high-speed railway lines compared with traditional ballasted tracks, the slab track still sustains some structural damage caused by train load and temperature load in the operation process. In practice, the wide and narrow joints between the track slabs have presented deficiencies, such as concrete loss and damage, and cracking at joints (shown in Figure 2) and arches, etc., in recent years. The longitudinal continuity and stability of the ballastless track are seriously weakened by the damage to the wide and narrow joint position. Therefore, it is necessary to study the mechanism of wide and narrow joint issues and to provide solutions for such joints' maintenance and repair. At present, most of the studies on wide and narrow joints of ballastless track mainly focuses on the generation of cracks and static and dynamic characteristics of wide and narrow joints under temperature load and train load. However, this cannot be effectively combined with the construction process. The influence of wide and narrow joint damage on the force and deformation of the seamless line, in temperature rise and continuous high temperature load based on the finite element theory, is studied in reference [5]. The author claims that there are some problems in the original design concept, and that longitudinal connecting reinforcement does not provide pre-pressure on wide joint concrete. Reference [6] investigated the influence of temperature load, interlayer state, and material quality on concrete damage at wide joints using the plastic damage constitutive model of concrete, and analyzed the causes of wide joint damage. Finite element simulation analysis on the effect of different tension-drawing processes on the force, exerted on the rail structure, was carried out in reference [7]. It was concluded that the tension-drawing of the longitudinal reinforcement does not exert great pre-pressure on narrow joint concrete, and its effect on temperature resistance is not obvious. Figure 1: CRTSII slab ballastless track (unit: mm). Figure 2: Cracking at wide and narrow joints. It can be seen that there is a design concept problem in the longitudinal connection of ballastless tracks. However, so far, very few studies have been published on the damage caused by the tensioning of longitudinal reinforcement in the construction stage; also, there is no research on fixing this problematic design concept. Based on the above analysis, this paper is divided into two parts (construction stage and operation stage) to study the tensile properties of longitudinal reinforcement.