Screw spikes with a special forged head are track fasteners used in railway turnouts. The premature damage of these screws has proven a reoccurring problem in short turnouts at Tampere railway yard. The purpose of the screw spikes, together with other fastening components, is to prevent lateral displacement of the rail and to maintain the track gauge. The breaking of several adjacent screw spikes weakens the rail fastening system's ability to resist lateral movement of the rail. This may result in critical lateral movement in the rail and eventually lead to train derailment. As well as posing a threat to railway safety, screw spike damage also causes additional maintenance cost and possible delays in railway traffic.The aim of this study was to investigate why the screws spikes suffer premature damage in short turnouts at Tampere railway yard and whether the damage is connected to a loading caused by particular type of rolling stock. The extent of the screw spike damages were investigated at the rail yard. The fracture surfaces of broken screw spikes were examined with a macroscopic camera and the photos revealed clear surface features of fatigue fractures. Tensile tests conducted to screw spikes manufactured in different years, revealed that the investigated broken screw spikes were most likely made of 4.6 strength grade steel, although the minimum requirement for screw spike strength grade is currently 5.6.The load environment of the screw spikes was measured with strain gauges instrumented in the screw spikes as a part of experimental field study. The lateral displacement of the turnout rail was also measured with displacement sensors. The strain measuring results showed that the load caused by commuter trains is not evenly distributed among the four screw spikes in the rail fastening. The strain in one of screw spikes in the middle of the diverging check rail was five times greater than the strain obtained from the comparative measuring point.The results gave no evidence to suspect that the failure of the screw spikes is connected to a specific type of rolling stock. Instead, the results gave evidence that the trains traversing the turnout in trailing direction caused a more wearing variable-amplitude loading to the screw spikes than the trains traversing in facing direction.
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