Abstract
The heat flux density of solar radiation, received by each surface of a double-block ballastless track bed slab, is closely related to its alignment and geographical latitude. In this work, a temperature field analysis model based on experimental data, the theories of solar radiation, and boundary heat transfer is established by a CRTS-I double-block ballastless track structure using the ABAQUS finite element software to investigate the influence of different alignments and geographical latitudes of the temperature field. The horizontal and vertical temperature gradients of the ballast bed plate were found to be in the most adverse conditions when the angle αn between the normal direction of the ballastless track slab bedside surface and positive south direction was equal to 90°. The standard deviation of the overall temperature gradient of the ballast bed was found to be at lowest and standard value of the dispersion degree was highest at an αn of 90°: 14.138 and 10.446°C/m, respectively. The horizontal and vertical temperature gradients in high latitudes and coastal areas were found to be more detrimental than that in the low latitudes or inland areas. These results can provide references for how to avoid high-temperature loading during railway line selection and track design.
Highlights
The influence of temperature on the structure of ballastless track is very obvious
The double-block ballastless track (DBT) structure proposed by the China Rail Transit Summit with a convex stop for longitudinal limit has the characteristics of good structural stress, low construction difficulty, high line accuracy, and good track smoothness
The CRTS-I DBT structure under investigation comprised the following: a continuously poured roadbed with a thickness of 260 mm and width of 2800 mm,[17] a continuously poured concrete support layer with a width of 3400 mm and thickness of 300 mm, a C60 concrete structure adapted to a sleeper structure,[18] a C40 reinforced concrete structure adapted to roadbed board, and a C15 concrete structure as a support layer
Summary
The influence of temperature on the structure of ballastless track is very obvious. In the natural environment, the temperature of the surface and internal of the concrete engineering structure change at any time, thereby causing temperature deformation. Many studies have focused on temperature field models of orbital structures, few have been focused on the impact of line direction, geographical latitude, and natural environment[6] on the temperature gradient of a track slab. Qc qr ð1Þ where l is the coefficient of thermal conductivity (J/mÁsÁK), T is the temperature field of the track plate, n is the unit vector in the normal direction, Q is the solar radiation heat flux density, qr is the radiation heat transfer and heat flux density, and qc is the convection heat transfer density.[11] Equation (2) is used to obtain qr and qc qc = hcDt qr = hrDt À qra ð2Þ here, hc is the convection heat transfer coefficient, hc = 3.06v + 4.11 (W/(m2Ák)), where v is the wind speed, assuming 1 m/s; Dt is the temperature difference between the surface of the orbital structure and the atmosphere; hr is the radiation heat transfer coefficient,[12] hr = 0.035Dt + 5.44 (W/(m2Ák)); and qra is the heat flow constant related with the weather (W/ m2). Density (ton/mm3) Thermal conductivity (mw/mmÁK) Specific heat capacity (mJ/tonÁK) Density (ton/mm3) Thermal conductivity (mW/mmÁK) Specific heat capacity (mJ/tonÁK) Density (ton/mm3) Thermal conductivity (mW/mmÁK) Specific heat capacity (mJ/tonÁK)
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