Research On The Parameter Optimization Of The Embedded Track Structure Of The Modern TRAM

The development of tram has experienced emergence, decline and revival. In recent years, China has also set off a boom in the construction of tram. According to statistics, by now Beijing, Shanghai, Tianjin and Guangdong have planned more than 50 modern tram lines, the planning mileage is up to more than 1300 kilometers, with a total investment over 300 billion RMB. The embedded structure, which is applied widely in modern tram, is very different from railway and subway in key parameters of track structure design like rail type, rail fixed mode, load form and structural mechanical. Taking into account the current lack of systematic research on tram structure, especially in dynamic interaction between tram and embedded track as well as track structure parameter optimization, further study on modern tram is necessary. Therefore, this paper established both static and dynamic mechanical models of tram system to analyze track structure parameters, after which the optimization range of relevant parameters is put forward. This paper provides certain guidance in formulation of modern tram technical standard, as well as in design and research of modern tram embedded track structure. The main contents are as follows:(1) The development and research status of modern tram at home and abroad are summarized, the existing mechanical analysis methods of embedded track structureare studied too. On that basis, the significance and research direction of study on parameters of embedded track structure are cleared.(2) Taking into account that the embedded track structure not only bears the load from tram, but also suffers from road traffic, static calculation models of embedded track structure in the independent road right area and mixed road right area are established according to the characteristics of the embedded track structure. Static studies on parameters optimization of embedded track structure without fastening systems in both the independent road right area and mixed road right area are conducted. Through static analysis the vertical track support stiffness and the optimization range of foundation stiffness under the slab are initially identified. It is suggested that the range of the elastic modulus of the filling material atrail waist takes 10-15MPa.(3) Dynamic model of 70%-low-floor modern tram vehicle is established based on the dynamics theory of multi rigid body; using finite element analysis method a dynamic model of the embedded track structure is established with consideration of its characteristics. Under the guidance of the wheel-rail contact theory, coupling the established vehicle and track models to build the modern tram-embedded track of rigid flexible coupling dynamics model. The dynamic model is validated and advanced by referring to the existing literature research results. From the aspect of dynamics, rail type and rail fixing method are analyzed, also optimization study on the track structure stiffness and damping parameter of embedded track without fastening systems are conducted. Through dynamic analysis together with related research results of statics, it is suggested that 59R2 groove rail is superior for embedded rail track structure, on the straight line the performance of track structure without fastening systems is better than fastening system embedded track structure, for small radius curve section, whether to set fixed fastening rail or not should be considered by analyzing the rail and filling stress status comprehensively and in accordance with the specific conditions in line; it is suggested that the range of the supporting stiffness under the rail takes30-40kN/mm; the track support vertical damping should not be higher than75kN·s/m; the foundation stiffness under the slab should be within 60-76MPa/m.