Numerical investigation on the failure mode of the upper shear hinge in steel spring floating slab track

Abstract

Fracture on hinge bars and fixed bolts of upper shear hinges is a common problem in prefabricated steel spring floating slab tracks (SSFST), adversely affecting train operation safety and comfort. To investigate the potential failure modes, this paper established a four-slab SSFST model to analyze the force condition of upper shear hinges. Force transmission between floating slabs as well as the stress level of the hinge bars and fixed bolts under the most unfavorable vehicle cases were respectively simulated by the structural mechanics method (SMM) and the FEA software ABAQUS. Stress influence lines of hinge bars and fixed bolts under the moving vehicle load resulting from ABAQUS were extracted to evaluate the fatigue behavior based on the fatigue S-N curve by the post-processing software FE-SAFE. Furthermore, the influence of different pre-tightening force on fixed bolts’ fatigue behavior was discussed. The results of the two simulation methods match well, suggesting that force between floating slabs is mainly transmitted by rails, while shear hinges only account for about 1/3 of the bending moment and 1/5 of the shearing force. Hinge bars and fixed bolts are both sufficient in strength, yet fatigue problem is likely to happen to the latter. The fatigue failure mode and location of fixed bolts are related to the value of pre-tightening force. Large stress range or high stress mean always exists as the pre-tightening force varies, meaning that bolt fatigue is an intrinsic failure mode of the upper shear hinge in SSFST.