# Research on Optimization Design of Geometric Parameters of a Novel Frame-Embedded Track (NFET)
## 5 Discussion  
According to the shortcomings of the existing tram track structure, a novel frame-embedded track (NFET) with transverse connecting beams has been developed. Through the establishment of a finite element model of the NFET, the static characteristics of NFET structure in two different construction stages were systematically analyzed with the beam width, the thickness of the lower slab of the rail seats, and the cable and the drainage facilities as the research variables.  
In the hoisting stage, with the increase of beam width, the displacement of NFET structure did not change significantly, and the stress at the lifting hole increased continuously, but the stress at the beam remained unchanged. With the increase of the thickness of the lower slab of the rail seats, the displacement in the thickness of the lower slab of the rail groove did not change obviously, but the displacement of the plate end decreased; the stress at the lifting holes increased slightly, and the stress at the beam decreased slightly. When considering the cable and the drainage facilities, the stress at the lifting holes increased, while the displacement and stress at other measuring points remained unchanged. It can be seen that, at this stage, the thickness of the lower slab of the rail seats and the cable and the drainage facilities had no significant effect on the mechanical properties of the NFET structure. However, the width of the beam is the determining factor for the stress at the lifting holes.  
In the driving stage, the vertical displacement of the same measuring point at the bottom of the rail seats and the bottom of the cast-in-place concrete slab was almost the same. It was not affected by the changes of the width of the beam, the thickness of the lower slab of the rail seats, and the cable and the drainage facilities. When the beam width was 150 mm, the stress at the beam of rail seals was small. When the beam width was  
Figure 17: The vertical stress of the rail seats and the bottom of the cast-in-place concrete during the running period. (**a**) Rail seats and (**b**) cast-in-place concrete.  
240 mm, the stress at the bottom of the cast-in-place concrete slab end and at the beginning of settlement reached the minimum. In particular, the stress of the cast-in-place concrete structure was generally greater than that of the prefabricated rail seats. With the increase of the thickness of the lower slab of the rail seats, the stress at the prefabricated rail seats beam decreased continuously and changed most significantly in the 80-100 mm range, then tended to be gentle, and there were no significant changes in the other measuring points. When the cable and the drainage facilities are considered, the stress at the middle and upper parts of the prefabricated rail seats slab, the middle and bottom of the cast-in-place concrete slab, and the beginning of the settlement increased slightly, while the stress at other measuring points remained unchanged, or even decreased slightly.  
Of course, the study also has some limitations. First of all, in terms of research methods, this paper only uses numerical simulation, and subsequent research can consider continuing to carry out model tests or physical tests on the basis of this paper. Secondly, in terms of research content, this paper only studies the static performance of an NFET structure under conventional loads and has not conducted in-depth research on its dynamic performance and some special loads (such as earthquake). Moreover, in terms of the scope of application, this paper only studies the feasibility of NFET structure in the tram field and its applicability in other rail transits, such as subway, high-speed railway, and heavy haul railway, remains to be discussed.