11. Method for Identifying Potentially Critical Locations of Loose Bearing Based on On-board-measured Track Geometry

In steel railway bridges, loose bearing accompanied by vibration at the support points may occur when trains pass. Since loose bearing can lead to issues such as fatigue cracks, engineers have traditionally conducted periodic on-site inspections, visually checking each bridge one by one. This process has required a significant amount of manpower.
Therefore, if loose bearing locations can be identified using track geometry measured on-board, it would be possible to narrow down the inspection targets and significantly reduce the workload. However, it has been difficult to extract subtle displacements caused by loose bearing from on-board-measured track geometry, and no effective method had been developed to achieve this.

To address this, we first developed a numerical analysis method and clarified the characteristic increase in track geometry amplitude at locations with loose bearing. Based on this property, we developed a method for identifying loose bearing locations by using the amplitude of track geometry obtained by subtracting the track geometry measured under unloaded condition (recorded by a simplified track measurement device) from the track geometry measured under loaded condition (recorded by a track inspection car) as a detection indicator. This method was applied to 137 bearing points along an actual railway section with multiple consecutive simply supported steel bridges with ballastless steel tracks. As a result, all 14 bearing points that had previously been identified as critical by the railway operator were successfully detected due to vibration or due to an uplift gap of 0.5 mm or more observed during visual inspections (Figure 1).

This method is applicable to sections with consecutive steel bridges with ballastless steel tracks, such as long-span bridges, and enables the screening of loose bearing locations that require visual inspection, thereby contributing to a reduction in inspection workload. It is also planned to be used as a subsystem of the integrated analysis platform.