# Study on the Mechanical Characteristics of the Sleeper Slab Track on a Long-Span Steel Truss Bridge
## 1 Introduction
However, some scholars proposed that it is prone to crack under the influence of temperature and bridge deformation, which affects the durability of the structure [12; 13; 14]. Compared with the traditional ballasted track and ballastless track, the sleeper track on the open deck has a simpler structure with a smaller secondary dead load. Wooden sleepers are the main track structure used on the open deck of steel truss bridges. However, wooden sleepers have poor durability and can easily decay and crack. Scholars from all over the world began to look for new materials to replace wooden sleepers [15; 16]. In the work of [PERSON] et al., the mechanical properties of composite sleepers and wooden sleepers were compared and analyzed by the finite element method. The research showed that the performance of composite sleepers is equivalent to that of wooden sleepers, and only one-third of the volume of standard wooden sleepers is needed [17]. [PERSON] et al. used the four-point static bending test on composite sleepers to study the strength and failure mechanisms [18]. Data from the above research suggest that composite sleepers have good performance in flexural behavior. [PERSON] et al. proposed to coat epoxy-based polymer concrete on the sleeper surface to protect the sleeper from unfavorable environments and increase the strength of the rail-seat area [19]. After summarizing the material properties of various composite sleepers, [PERSON] et al. pointed out the problems existing in the application and development of composite sleepers [20; 21]. The primary obstacles to the composite sleepers are their prohibitive cost, low anchorage capability of holding screws, formation of voids in the body of the sleeper, permanent deformation due to creep and temperature variations, and insufficient lateral resistance. Nansha Port Railway in Guangzhou is a mixed passenger and freight railway with a design speed of 120 km/h. It has a through bridge with a steel truss and arch. The total length of the bridge is 996 m. In order to prolong the maintenance period of the track structure and reduce the secondary dead load of the bridge, a new type of concrete sleeper slab track structure on the open deck was adopted. The integrity of the structure was improved by prefabricating two sleepers into one and setting up vertical and horizontal limit devices. The adjusting cushion, sleeper slab, and cushion under the slab were set up between the sleeper slab and the steel beam. High strength bolts were used to connect the structure vertically, as shown in Figure 1. In practical engineering, the train operation produces a large vertical force and when the train passes through the curve section or has a hunting motion, it produces a large transverse force. Furthermore, the train operation, breaking, and passing through the ramp also produces a large longitudinal force. The coupling effect of the three-dimensional force has a great impact on the track structure and even damages it [22; 23]. In order to study the mechanical properties and long-term performance of the new type of sleeper slab track structure, this paper carried out a full-scale indoor modal loading test of the concrete sleeper slab track structure to provide a reference for the engineering application.