Image measurement and numerical simulation of rail displacement distribution during train passage at a bridge transition zone

Settlement of the embankment on bridge transition zones is well known as one of the weak points in railway infrastructure. However, few field measurement studies have captured the wide-ranging and complex behavior of rails during train passage at such bridge–abutment–embankment boundary zones. In this study, multiple cameras were used to record the rail displacement responses during train passage at the bridge transition zone on a local railway line in Japan. The rail displacements obtained from each camera using digital image correlation (DIC) methods were combined to estimate as the displacement distribution. The results demonstrated that the rail at the bridge transition zone exhibits a seesaw-like motion, pivoting around the abutment located at the interface between the bridge and the embankment during train passage. Furthermore, to reproduce this complex phenomenon, a static nonlinear numerical simulation method was proposed using a rail model supported by springs with bilinear stiffness, which allows for consideration of hanging sleepers. By updating the hanging amount and the secondary stiffness of the supporting springs based on the image measurement results, it was shown that the proposed numerical method can successfully reproduce the complex rail behavior observed in the bridge transition zone.