Abstract:Temperature effect is one of the main factors that influence the performance of box girder-track in high speed railway. Through the continuous temperature field monitoring of CRTS I twin-block ballastless track with 32 m simple supported beam bridge for the entire year,the time-dependent temperature variation and the regular distribution of temperature gradient were analyzed. The representative values of temperature differences with a certain return period were ascertained by Higher Moment Method. Based on the 16560 data at each measurement point,the vertical temperature load modes of box girder-track in southeastern China were suggested. The analysis results reveal that the goodness-of-fit is increased by using the first Fourier series to simulate the temperature fluctuation characteristics of sunny day,and the same season fitting parameters a,b,ω and φ decrease from top to bottom and the temperature fluctuation amplitude of a is close to 0℃ as the depth increases. The diurnal variation characteristics of each section on sunny days are basically similar in the different seasons,and the positive and negative temperature gradients approximately appear around 11:00 to 21:00 and 01:00 to 9:00,respectively. The positive and negative representative values of box girder-track vertically are 14.87℃ and -6.3℃ with the exceedance probability of 0.01,respectively. And the positive and negative representative values of the top plate and bottom plate are 13.74℃,-3.54℃ and 2.38℃,-1.12℃ with the exceedance probability of 0.01,respectively. The values of positive and negative temperature difference of top plate are fitted by the exponential form,which is approached to the temperature load modes of the concrete box girder in Chinese railway bridge code. The values of bottom plate are fitted by linear form. The correlation coefficients of the two fitting forms are more than 0.99,which can be used for the engineering application and reference.

Abstract:Based on the results of continuous observations of the longitudinally connected ballastless track on curved bridges, the time-dependent deformations of vertical temperature gradient in different kinds of weather were discussed. Based on statistics and curve-fitting, raised temperature load models were fit for typical areas in our country. The analysis results reveal that the changing of the temperature in the track structure is fast, the temperature changing value of surface was 16.0℃ in maximum and 8.0℃ in average, the temperature changing value became small, and the time of maximum temperature come late with the increase of distance to surface, and at the bottom of the track structure, the temperature changing value was 1.5 ℃ in maximum, 0.8 ℃ in average, the fitting curve of vertical temperature gradient in longitudinally connected ballastless track on curve bridge can be exponential curve, and the distribution law matches the provisions about the vertical temperature gradient of the code for the design of railway bridges and culverts in China.

Abstract:A beam-rail-pier 3D finite element model was built by adopting the mechanism of ideal elastic-plastic ballast resistance under the background of a 156m long-span simply supported steel truss bridge on Huangling-Hancheng-Houma Railway line. The purpose was to study the distribution of longitudinal force due to temperature variations, bridge deflection, braking force and the breaking force of long rail in steel truss bridges. The influences of design parameters on longitudinal forces, such as the bearing arrangements of adjacent simply supported bridges, pier longitudinal stiffness and the arrangement of small resistance fasteners, were also discussed. It has been shown that the longitudinal force due to temperature variations plays a major role. Secondly, the bearing of adjacent simply supported bridge should be in the same direction as the steel truss bridge. Thirdly, the longitudinal force due to temperature variations and structural deflection increases and the braking force decreases as the pier longitudinal stiffness increases. Finally, the small resistance fasteners have a good effect on the longitudinal force due to temperature variations, which can reduce the force by 36% after being installed.