Finite Element Analysis of Controlled-Slip Bolted Shear Connectors for Interface Deformation Coordination in Negative-Moment Regions of Steel–UHPC Composite Beams
To improve deformation compatibility in the negative-moment regions of continuous steel–ultra-high-performance concrete (UHPC) composite girders, this study investigates a controlled-slip bolted shear connector in which bolt-hole clearance is intentionally used as a deformation-release parameter. A three-dimensional nonlinear push-out finite element model was developed in ABAQUS and validated against reported high-strength bolted connector tests. Parametric analyses were then conducted to clarify the effects of bolt-hole clearance, bolt preload, and interface friction on the load–slip response, local UHPC bearing damage, and bolt stress state. The results show that increasing the radial clearance from 0.1 mm to 2.0 mm increases the peak slip from 6.51 mm to 9.17 mm, whereas the peak resistance remains within 661.79–693.86 kN. Bolt preload mainly changes the initial frictional restraint and slip initiation, but has limited influence on the ultimate resistance. Damage and stress distributions further indicate that larger clearance delays UHPC hole-wall bearing damage, while increasing the bending–shear demand on the bolt shank. The results indicate that reserved bolt-hole clearance can be used to increase connector slip capacity while maintaining a comparable shear-resistance level within the investigated parameter range.