## 1 Introduction  
Train derailment not only causes economic losses, but also leads to the loss of life [1, 2]. Preventing train derailment has always been pursuit of researchers [3, 4, 5, 6, 7]. Guardrails are commonly employed to avoid wheel derailment, as well as the derailed train hitting the bridge or falling from the bridge. Furthermore, they have become a crucial part of the ballasted track structure on the bridge.  
Many researchers have performed numerical simulations and experiments to examine the functioning principle of guardrails and optimize the profile, as well as the installation parameters, of guardrails. Ongoing research has resulted in a continuous strengthening of the function of the guardrails [8; 9; 10; 11; 12; 13; 14]. Due to the connection between the guardrails and the stock rails through the sleeper and fastener, guardrails laying on the bridge can undertake the load of the CWR together with the stock rail, thereby affecting the mechanical behavior of the latter. In a feasibility study of laying 50 m rails on simply supported bridges, [PERSON] et al. [15] first proved that the existence of guardrails and the longitudinal resistance of guardrail fasteners could affect the mechanical behavior of the 50 m stock rails. Additionally, they suggested that the guardrails should be considered in the reserved joint gap design of the 50 m stock rails on the bridge. [PERSON] et al. [16] showed that the guardrails affect the stability of the CWR, and only when the temperature force aggregated in the guardrails is small, the guardrails could improve the stability of the CWR. As a result, these studies confirm that the presence of an appropriate guardrail system on the bridge also influences the track-bridge interaction of the CWR on the bridge.  
The study on track-bridge interaction essentially originates from the calculation of the distribution of train braking and traction force in rails and bridges [17]. Subsequently, scholars across the globe have performed pioneering research by developing calculation models, track-bridge longitudinal resistance models, calculation methods [18; 19; 20], and load combinations. The track structure models range from traditional ballast tracks to various types of ballastless tracks [21; 22; 23; 24]. Additionally, there is a wide range of existing bridge models, from reinforced concrete bridges to long-span flexible steel bridges with a highly nonlinear geometry to curved bridges [25; 26; 27; 28]. The overall developed models of the CWR on bridges range from the truss model to the rail-beam-pier integrated model and the spatial solid model [29; 30; 31]. The calculation methods cover a broad range of approaches, such as the transfer matrix method and the Runge-Kutta method [32; 33]. Moreover, a solution algorithm for the corresponding nonlinear equation, including the generalized variational principle and the finite element method, has been widely utilized [34; 35]. The track-bridge longitudinal resistance models include the constant resistance model, the nonlinear resistance model accounting for the load history, and the resistance model considering the track frame effect [36; 37; 38]. The applied loads studied also cover single temperature load or train load, as well as various load combinations and special loads such as seismic load [39; 40]. However, the influence of guardrails on the track-bridge interaction has been ignored in these studies, and the impact on the reliability and safety of the CWR on the bridge is incalculable.  
Based on the above literature survey, this paper aims to carry out longitudinal resistance tests of the guardrail fastener and proposes a stock rail-guardrail-sleeper-beam-pier integrated simulation model to scrutinize the guardrail effect on the track-bridge interaction rules of the CWR. Further, the obtained rules can provide a solid basis and an appropriate reference for the refined design and maintenance of the CWR on the bridge.