# Study on the Mechanical Characteristics of the Sleeper Slab Track on a Long-Span Steel Truss Bridge
## 5 Conclusions  
In the present paper, full-scale laboratory tests on the sleeper slab track structure were proposed, consisting of the vertical static load test, vertical fatigue test, and horizontal resistance test. From the test results, the mechanical characteristics and fatigue behavior of the sleeper slab track were evaluated. The conclusions of this research are as follows.  
Figure 11: The main failure modes of structure. (**a**) Separation, (**b**) Crack, (**c**) Deformation of iron plate.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sine Cyclic Loading Numbers** & **1 Million** & **2 Million** & **3 Million** \\ \hline Transverse displacement/mm & 0.255 & 0.269 & 0.290 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Maximum transverse displacement of sleeper slab (relative steel beam).  
These experiments confirmed that after 3 million cycles of sine cyclic loading, the sleeper slab track is considered to maintain excellent mechanical properties. As the number of loading cycles increased, the strain of the sleeper slab and self-compacting cushion varied slowly. The unfavorable positions were found in the inner side of the sleeper, the mid-span of the slab, and the middle of the short side of the cushion. Compared with the strain, the change in vertical displacement was considered to be more obvious due to the stiffness change under the action of cyclic loading.  
The results of the transverse ultimate resistance test indicate that failure occurred in the track structure when the transverse force reached 413.4 kN. The main failure modes were separation between the self-compacting concrete cushion and steel beam, crack between the sleeper slab and cushion, and deformation of the iron plate at the bolt position. In addition, the longitudinal resistance test also showed that the track structure can still bear a longitudinal force of up to 100 kN after transverse failure.  
The new type of track structure proposed in this paper is planned to be applied to the long-span steel truss bridge to overcome the weaknesses of the traditional track structure on the open deck, such as poor integrity, difficult sustenance of track geometry, and heavy maintenance work. The main purposes of the current study were to verify the applicability of the sleeper slab track on the long-span steel truss bridge and to investigate the mechanical characteristics during the fatigue process with an experimental method. In order to investigate the performance parameters of the track structure more comprehensively, future work to be performed by the authors will be focused on the precise numerical simulation of the track structure.  
Conceptualization, Z.Z. ([PERSON]) and W.W.; methodology, X.H. and D.W.; software, X.H.; validation, X.H. and D.W.; formal analysis, X.H. and D.W.; investigation, X.H. and D.W.; re-sources, Z.Z. ([PERSON]), B.Z., and Z.Z. ([PERSON]); data curation, X.H. and D.W.; wrti-ing--original draft preparation, X.H.; writing--review and editing, W.W.; visualization, X.H. and D.W.; supervision, Z.Z. and W.W.; project administration, X.H. and D.W.; funding acquisition, Z.Z. ([PERSON]), B.Z., and Z.Z. ([PERSON]). All authors have read and agreed to the pub-ished version of the manuscript.  
This research was funded by the High-speed Railway Joint Fund of National Natural Science Foundation of China, grant number U1734208; the Hunan Provincial Natural Science Foundation of China, grant number 2019 JJ40384; and the Fundamental Research Funds for the Central Universities of Central South University, grant number 2019 zzts873.  
All data, models, and code generated or used during the study appear in the submitted article.  
The authors declare no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.