# Track-Bridge Interaction of CWR on Chinese Large-Span Bridge of High-Speed Railway
## 3 Track-Bridge Interaction Law of Different Bridge Types
### Cable-Stayed Bridge
#### 3.3.2 Track-Bridge Interaction Law  
In different structural systems, the diagram of rail braking force and bending force when the train passes through the whole bridge is as shown in Figures 5 and 6 [39]. The distribution law of the additional longitudinal force of the seamless track on the cable-stayed bridge is the same as that on the ordinary bridge. The change of the cable stiffness has little effect on the longitudinal interaction of the seamless track on the bridge. The influence is smaller. When designing the seamless track on the bridge, it is recommended that the influence of the rigidity changes of the stay cables and the main tower should not be considered [40; 41]. The additional force of rail expansion and contraction on the long-span railway cable-stayed bridge is obviously greater than the additional force of deflection [42; 43]. When calculating the expansion and contraction force of the rails of a concrete cable-stayed bridge, it is recommended to load calculations based on the beam body heating of 15 \({}^{\circ}\)C and the cable heating of 40 \({}^{\circ}\)C [44]. In the calculation, the geometric nonlinearity and initial internal force of the cable-stayed bridge can be ignored, and the cable-stayed bridge can even be simplified as a continuous beam bridge with telescopic beams at both ends and fixed bearings in the middle of the span [45; 46]. However, the influence of adjacent bridges must be considered. When the number of adjacent simply supported bridges is greater than six spans, it can be simplified as six spans [47]. Figure 4: Finite element model of cable-stayed bridge and CWR (unit: mm). Figure 3: U-shaped beam section (unit: cm). When calculating the bending force of the rail, the pile foundation should be considered [48]. The load can be placed on the main span of the cable-stayed bridge and its adjacent span, or the load can be placed only on the main span of the cable-stayed bridge, and there is no need to consider changes in the direction of the train entering the bridge [45]. The structural system of the cable-stayed bridge is relatively flexible, and the rail near the middle of the span bears a large bending force [49]. When the vertical train load is loaded on the mid-span of a cable-stayed bridge, the vertical deformation and curvature of each member are greatly affected [50]. When calculating the interaction between the beam and the rail under braking, the main tower and stay cable of the cable-stayed bridge do not change the transmission  
Figure 5: Rail bending stress under vertical load. Figure 6: Rail braking stress under train braking. mechanism of the braking force, so the existing CWR checking method on the bridge can still be used for the checking calculation [51], and the static method can be used in practical engineering application [52]. The construction of high-speed railway cable-stayed bridges in areas with high wind speeds requires consideration of the additional force on the steel rails caused by wind loads on the towers [48]. When constructing a cable-stayed high-speed railway bridge in an area where the basic wind pressure exceeds 0.5 kW\(\cdot\)m\({}^{-2}\), it is necessary to check the influence of the pylon on the additional force of the rail under the action of the longitudinal wind load [44]. In order to reduce the additional force on the steel rails of the cable-stayed bridge, the following methods can be adopted: (1) The longitudinal restraint of the high-speed railway cable-stayed bridge can be the consolidation of tower beams or the installation of fixed supports between tower beams, and other supports are set as longitudinal sliding support [44; 48]. (2) When selecting the support arrangement of the simply supported beams at both ends of the cable-stayed bridge, the fixed support is set near the side of the cable-stayed bridge [47]. (3) The groove section can also effectively reduce the deflection of the rail [48].