Load transfer mechanism and design strength of hybrid bolted joint with friction- and bearing-type connections

Long slip-critical bolted joints are extensively used in steel-bridge construction to accommodate increasing traffic loads and optimise steel components. However, as the joint length increases, challenges arise owing to interference with secondary members, uneven bolt force distribution leading to premature failure, and reduced serviceability limit strength. Existing design codes incorporate reduction factors based on joint length to address these issues. This study proposes a hybrid bolt joint that combines friction and bearing-type bolted connections to reduce the joint length while maintaining or improving strength. Finite element analysis was used to investigate the interactive effects of bearing and friction connections, load sharing of hybrid connections, component deformation, and reductions in friction and bearing forces. The results show that the hybrid joint exhibits a uniform load distribution among the friction bolts but an uneven bearing force distribution among the bearing bolts, with the foremost bolt experiencing severe friction force loss. An effective correction factor was proposed to account for the reduction in friction and bearing forces. This study defines the serviceability limit state based on bolt shank shear yielding and provides recommendations for the strength assessment and design of hybrid bolted joints ( α s F s + α b F b ). The results contribute to the development of rational compact joints for steel-bridge construction and address the challenges associated with long multi-row bolted joints. • Reveals interactive effects between friction and bearing load transfer by using FEM. • Uneven bearing force causes friction loss in the front bolt from shear bending. • Correction factors are applied to assess both friction and bearing forces effectively. • Hybrid connection SLSs are defined by bolt shear yield and net cross-section yield. • Hybrid joint can provide more strength with fewer bolts compared to friction type.