Long-term friction performance monitoring of sliding layer in China railway track system Ⅱ slab track on bridge superstructure

Abstract

The sliding layer is an important component of the China Railway Track System (CRTS) Ⅱ slab track on bridges, and its friction performance has a significant influence on the intensity of track–bridge interaction (TBI). However, the friction performance deterioration of this sliding layer under actual repeated abrasion and harsh environmental conditions is difficult to grasp since structural health monitoring implementation into in-service high-speed railway tracks is extremely hard to be permitted and only limited valuable monitoring datasets are available at present. In this study, the friction performance degradation of the sliding layer was therefore investigated using long-term monitoring data from a multi-span simply supported box girder bridge. First, the friction-induced strain in the base plate was decoupled using the monitored strain at the fixing point and mid-span based on mechanical properties of TBI. Then, structural health monitoring and finite element analysis both indicated an approximately linear relationship between the decoupled friction-induced strain and the temperature of the investigated bridge under certain circumstances. Furthermore, the correspondence between the slope of this linear relationship and the friction coefficient was modelled. Finally, the friction coefficients of the sliding layers on target spans were identified using 4 years of monitoring data and the established correspondence model to analyse the statistical characteristics and degradation performance of the layers. This investigation of the friction performance degradation of the sliding layer in the CRTS II slab track system provides guidance for future maintenance and replacement decision making.

Stiffness identification of fixing device in CRTS II slab track based on long-term monitoring data

“…18 The interlaminar friction behavior between the base plate and bridge was defined by the Coulomb friction model, and the critical slip between them was set as 0.5 mm. 37 In addition, the friction coefficient of the sliding layer was obtained from a previous study, 21 and the friction coefficient between the base plate and friction plate was set as 0.7. 11 The interlaminar constitutive laws in the track–bridge system mentioned above are available in the previous research, 21 and the material properties of track components are shown in Table 1.…”

“…37 In addition, the friction coefficient of the sliding layer was obtained from a previous study, 21 and the friction coefficient between the base plate and friction plate was set as 0.7. 11 The interlaminar constitutive laws in the track–bridge system mentioned above are available in the previous research, 21 and the material properties of track components are shown in Table 1. With respect to the boundary condition, the bottom of the friction plates was fixed, and the two ends of the rail were fixed in the longitudinal direction because they were continuous in this direction.…”

“…The monitored temperature from July 29, 2015 to August 5, 2015 was applied to the FEM of the investigated bridge as the temperature load, and the friction coefficient of the sliding layer was set as 0.23 according to a previous study. 21 The strain difference values Δ ε 3 FEM under six working conditions (NO1–NO6) were obtained from FEM simulations, and a comparison between the simulated strain difference Δ ε 3 FEM and the monitored strain difference Δ ε 3 is shown in Figure 6.…”

“…The mapping function is expressed as Equation ( 4), whose parameters in each year were illustrated. It should be noted that the stiffness of fixing device cannot be identified if the friction coefficient of sliding layer was unknown, so the result of the previous research 21 would be the cornerstone of the current research:…”

“…With respect to railway health motoring, the friction performance of sliding layer has been revealed using the monitored strain in base plate at the inner side of the fixing device and the mid-span of bridge. 21 The defects detection method of railway, 22 the monitoring of rail corrugation 23 , and the condition assessment of HSR track 24 have also been reported in recent years. Furthermore, there are many researches about condition assignment [25][26][27][28] and experimental method 29,30 of structures, and the stiffness modeling methods of machines [31][32][33] have been studied.…”