Numerical study of bolt loosening in shear-loaded joints under cyclic loading

Resumo

Although many steel structures used in civil engineering are not exposed to large cyclic loads or a high number of cycles to develop significant fatigue damage, this phenomenon cannot be completely ruled out, especially in connection systems. Bolted joints, widely used for their practicality in assembly and disassembly, may show loss of fastening over time when subjected to cyclic stresses.Depending on the way in which the load is transmitted, these connections may be subjected to axial tensile, shear, torsion or lever action stresses. The progressive decrease in clamping force, caused by relative slippage or relaxation of the assembly, increases maintenance requirements and may compromise structural safety if not properly controlled.In this work, a finite element model is developed to simulate the loosening in bolted joints subjected to transverse or shear loads, in order to study the mechanical behavior and the evolution of the preload loss in bolts under cyclic actions. The model allows to analyze the influence of different geometrical parameters on the relative sliding between the bolted parts, as well as to evaluate the impact of these conditions on the service life of the connection. The results obtained are compared with existing criteria in the literature to validate the numerical approach and to propose improvements in the design or maintenance of this type of connections.