## 5 Conclusions  
This study provides a better understanding of the train-bridge interaction of long-span railway suspension bridges subjected to strike-slip fault. This study presents a detailed discussion of a nonlinear model of wheel-rail contact based on ANSYS/LS-DYNA software. A refined finite element model of train-bridge coupling system was established based on the nonlinear finite element software of ANSYS/LS-DYNA. The findings of this study can provide guidance for the seismic design and train running of long-span railway suspension bridges crossing faults and help improve the safety and efficiency of the railway transportation system. Therefore, the following conclusions are drawn:  
1. For long-span suspension bridges crossing left-lateral strike-slip faults, it is crucial to emphasize the substantial impact of the fling-step effect on PGRD, leading to amplified bridge responses. This effect is particularly pronounced in the transverse response at FCA = 90\({}^{\circ}\) and significantly influences the longitudinal response at lower FCA values. Consequently, PGRD plays a pivotal role in seismic bridge responses, with a direct correlation between the magnitude of the response and PGRD. 2. It is imperative to underscore the critical consequences of lateral seismic motion during fault dislocation, which profoundly affects the dynamic parameters of trains. In contrast, the influence of longitudinal seismic motion on the derailment coefficient is relatively minor. However, as seismic motion persists, longitudinal ground motion can lead to vertical displacements in the main beam, potentially causing the wheel-load-reduction rate to surpass permissible limits. 3. Within the context of strike-slip faults, it is worth noting that PGRD resulting from fault slips is predominantly governed by the low-frequency components of seismic waves, accounting for approximately 70% of its impact on train dynamic parameters. This underscores the necessity for trains to traverse large-span bridges before PGRD reaches its full formation to significantly mitigate dynamic indicators. Figure 14: Time histories of wheel–rail responses at FCA = 90\({}^{\circ}\): (**a–e**) derailment coefficient; (**f–j**) wheel-load-reduction rate; (**k–o**) lateral wheel–rail force (note: the time of occurrence is depicted on the lower horizontal axis for the peak value of case 1, while the time of occurrence is depicted on the upper horizontal axis for the peak value of case 2). Continuing to emphasize the importance of timing, if trains persist in traversing the bridge after the complete formation of PGRD, they will encounter a compounded effect. This effect combines additional track irregularities induced by PGRD with the high-frequency components of seismic waves, resulting in a progressive escalation of dynamic parameters that may ultimately breach established safety limits. It should be noted that the above conclusions are derived from the simulation analysis in this paper. The wheel-rail contact in the train-bridge system involves nonlinear dynamic behavior, and it is important to acknowledge that earthquakes are characterized by random vibrations. Seismic random analysis of the train-bridge coupled system is a highly complex issue. Therefore, additional numerical calculations and field experiments are necessary to provide further support for these conclusions. Conceptualization, S.C.; Software, S.C.; Validation, S.C.; Investigation, W.K., J.Y. and S.D. ; Data curation, S.C.; Writing--original draft, S.C.; Writing--review and editing, H.J. ; Funding acquisition, H.J. and S.Z. All authors have read and agreed to the published version of the manuscript. The research for this paper was supported partially by the National Science Foundation of China (No. 52178169 and No. 2021 YFB1600300), Science and Technology Plan of Sichuan Science and Technology Department (No. 2019 YJ0243 and No. 2020 YJ0081), and Major Systematic Projects of China Railway Corporation (No. P2018G007).