In current railway rails, trains are propelled by the rolling contact between iron wheels and iron rails, and the high frequency of train repetition on rails results in a significant load exertion on a very small area where the wheel and rail come into contact. Furthermore, a contact stress beyond the allowable stress of the rail may lead to cracks due to plastic deformation. The railway rail, which is the primary contact surface between the wheel and the rail, is prone to rolling contact fatigue cracks. Therefore, a thorough inspection and diagnosis of the condition of the cracks is necessary to prevent fracture. The Detailed Guideline on the Performance Evaluation of Track Facilities in South Korea specifies the detailed requirements for the methods and procedures for conducting track performance evaluations. However, diagnosing rail surface damage and determining the severity solely rely on visual inspection, which depends on the qualitative evaluation and subjective judgment of the inspector. Against this backdrop, rail surface defect detection was investigated using Fast R-CNN in this study. To test the feasibility of the model, we constructed a dataset of rail surface defect images. Through field investigation, 1300 images of rail surface defects were obtained. Aged rails collected from the field were processed, and 1300 images of internal defects were generated through SEM testing; therefore, a total of 1300 pieces of learning data were constructed. The detection results indicated that the mean average precision was 94.9%. The Fast R-CNN exhibited high efficiency in detecting rail surface defects, and it demonstrated a superior recognition performance compared with other algorithms.

This study evaluated the design and performance of an improved 3.5 MW floating photovoltaic (PV) power generation system consisting of fiber-reinforced polymer (FRP) members and its installation in the ash pond of a thermal power plant. The FRP design code of the American Society of Civil Engineers was used to design the structure. The safety of the structure was then confirmed using a finite element analysis indicating that the induced stresses were less than the allowable stresses dictated by the Korean Highway Bridge Design Code. An examination of the energy performance of the floating PV energy generation system after installation determined that the measured electricity production was as high as approximately 94% of the installed 3.5-MW capacity. The energy production of the floating PV structure with the improved design and module angles was found to increase by 7.65 times.

In this study, the measured track impact factor induced by the wheel–rail contact impact force of each test section (two continuous welded rails on slab tracks and rail joint on a ballasted track) was compared with the design track impact factor under service conditions of a curved light-rail transit system. The measured track impact factor (TIF) was estimated from the measured dynamic wheel load and vertical rail displacement at each test section. In the case of the rail joint section, the rail joint was found to directly affect the track impact factor. Moreover, the dynamic wheel load fluctuation and vertical rail displacement were found to be significantly greater than those of the continuous welded rails (CWRs) on slab tracks. In addition, vertical rail displacements were measured by field measurement and finite element analysis (FEA) was conducted to simulate dynamic wheel load on the jointed rail. Using the field measurements, the rate of dynamic wheel load fluctuation and the TIF were calculated for the CWR and rail joint sections. Subsequently, the calculated TIF values were analytically validated through a comparison with the measured vertical rail displacement, the results of FEA, and the designed TIF for rail joints and CWRs. Finally, the TIF measured by field measurement was compared with the result predicted by FEA. The difference between the results of field measurements and FEA for vertical rail displacement was within approximately 4%.

This study experimentally investigated the effects of rail pad corrosion on the performance of the direct fixation track on a long-span railway bridge in marine conditions. In this study, the dynamic behavior of a direct fixation track on a railway bridge in the presence of corroded rail pads, was determined. Field measurements in this study show that the replacement of corroded rail pads does not affect the track support stiffness. The hard rail pads used in direct fixation tracks are intended to provide electrical insulation rather than flexural track behavior, and so their influence on track support stiffness was found to be insignificant given their high spring stiffness. Additionally, samples of new and corroded rail pads were collected and the spring stiffness of rail pads were analyzed using static, dynamic, and aging tests. The spring stiffnesses of new and corroded rail pads were found to be similar. This means that spring stiffness is not significantly affected by corrosion, a finding that could be explained by the fact that the deformation due to passing train loads was extremely small. Therefore, even though the rail pads on the study bridge exhibited some surface corrosion, their function was not impaired, and they did not need replacement.

This study evaluated the structural stability of subway structures based on adjacent excavations by comparing automatically measured and numerically analyzed data. The reliability of the automated measurement methodology was evaluated by first applying probability statistical analysis to the measured results and then comparing these results with the numerically analyzed results. An improvement in the calculation method evaluation system, including the method of processing and analysis of the automatically measured data of subway structures through the average value of probability density, was proposed. As a result of the field measurement and numerical analysis, the measured results of tunnel displacement and track deformation exhibited some differences. However, it was determined that the construction stage and location where the maximum values of the tunnel displacement and track deformation occurred had similarities.

During railway operations, changes in the support conditions of sleepers, owing to various internal and external factors, can damage rails and concrete sleepers and alter the structural characteristics of gravel-ballasted tracks. However, current methods for evaluating gravel ballast conditions primarily rely on visual inspection. This study proposes a quantitative approach using modal testing to assess ballast conditions. This is achieved by analyzing and experimentally verifying the relationship between track ballast loosening (caused by subgrade deformation) and track support performance. Finite element analysis results and field experimental values were compared using spring stiffness as a parameter. The results showed that natural frequencies and mode shapes changed in response to variations in the vertical spring stiffness of the gravel-ballasted track. Therefore, the sleeper support condition of a gravel-ballasted track can be readily identified by analyzing the natural frequency corresponding to different sleeper support conditions.