Failure analysis of anchor bolt of rail fastening system for direct fixation track

The failures of the rail fastening systems have been reported in the curved sections of the subways in South Korea. These failures occur due to the lack of fastening strengths associated with two disc springs arranged in series, causing deformation of the base plate and large shear stresses on the anchor bolts. To demonstrate the failure mechanism, a series of on-site tests and numerical simulations have been conducted. The fastening strength can be enhanced by arranging three disc springs in parallel. When three disc springs were arranged in parallel, a significant reduction in vertical displacements of the rail supporting points, lateral displacements of the base plate and anchor bolts were observed compared to when two disc springs were arranged in series. The numerical simulations revealed that when two disc springs were arranged in series, the base plate can move, resulting in a high shear stress concentration on the anchor bolts. The long-term performance of the proposed setting has also been confirmed.