Mechanical Characteristic And Optimization Study On Longitudinal-Sleeper Track Structure On Subgrade Of Tram

Longitudinal-sleeper track structure on subgrade of tram is a new kind of rail-embeding track structure, it has many advantages such as less structure height, convenient construction and high smoothness, and haven’t been widespreadly used in china. This thesis sumarized the developent and research of tram track structure, establishmented the mechanics analysis model and finite element computing model of longitudinal-sleeper track structure on subgrade of shared-lane according to its characteristics, and studied the mechanical characteristic under the effect of different load and rational size parameters. The main research contents and achievements are as follows:(1) This thesis analysed three kinds of tramcar loading modes and obtained the longitudinal and horizontal maximum stress and bending moment in the track structure under the tramcar load, and it showed that the maximum longitudinal hogging moment is nearly half the value of maximum sagging moment; This thesis analysed four kinds of vehicle loading modes and the results indicate that the value of structure’s longitudinal and horizontal bending moment under the effect of vehicle load is greater than tramcar load, which is mainly due to the slab corner loading modes of vehicle.(2) When applied positive temperature gradient to the track structure, the constraints of gravity, rail and tramcar load was considered and it showed that the maximum longitudinal and horizontal warp stress of the track slab reached 66% and 17% of completely restrained condition; for the condition of negative temperature gradient, both slab-central tramcar load and slab-edge tramcar load was considered as constraint, and the maximum longitudinal and horizontal warp stress of the track slab reached 70% and 15% of completely restrained condition; when applied 20mm/20m scale of half-wave sine curve to the track structure to simulated the effect of uneven settlement on subgrade, the calculated maximum additional longitudinal sagging moment based on finite element method of elastic foundation reached 59% of simplified caculation based on rigid foundation.(3) This thesis studied the reasonable range of slab thickness and unit length of the track structure by considerations of reducing stress and deformation as well as project cost, which considered the effect of tramcar load, temperature gradient and uneven settlement on subgrade, led up to the conclusion that the reasonable slab thickness ranged between 0.15m to 0.20m, and reasonable unit length is in the range 5m-6m.