Bolt Force Monitoring Method Used in Maglev Structure Maintenance Based on Radial Strain on the Surface of Bolt Head

Abstract

The high-strength bolts are used to connect the steel columns and steel rail beams at the maglev maintenance base. The intense vibration due to active control of the maglev train may lead to the loosening of these bolts. Monitoring bolt axial force without damaging or removing is a significant method for bolt loosening judgment and vehicle-rail coupling research. In this paper, the radial-strain-based bolt sensor is produced by affixing the strain gauges on the bolt head surface. The performance is explored through finite element analysis and laboratory experiments. The results indicate a strong linear relationship between radial strain and axial force. In addition, arranging the strain gauges at 90-degree intervals on a circular ring on the bolt head can effectively reduce the influence of lateral forces and bending moments. Furthermore, this method is put into practice on the maglev experimental line of Tongji University. The results show that this method can effectively capture the variations of bolt force, thus ensuring the safety of the structure. This study fills the gap of bolt monitoring in the field of maglev infrastructure maintenance.