Load-bearing mechanism and full-process response characterization of a GFRP square tube bonded-bolted sleeve connection

The connection region of fiber reinforced polymer (FRP) components is a potential weak link in structures. Accurately reflecting the full-process behavior of the joint in structural scale calculations is a challenging aspect in the design of FRP composite structures. In this study, assembled glass fiber reinforced polymer (GFRP) lattice columns subject to compression loads were used as the structural background, and the focus was on the research of bonded-bolted sleeve connections for pultruded GFRP square tubes. Four hybrid joint specimens and two pure bolted joint specimens were designed and prepared. Axial compression static load tests were conducted, and a solid finite element (FE) model considering the failure behavior of the adhesive layer was established. The results indicate that the connection form exhibits a secondary load-carrying characteristic, and the overall mechanical behavior is derived from the superposition of the adhesive shear and bolt shear load transmitting mechanisms; Regarding specimens in this paper, the secondary peak load reaches 92% of the first, and the bearing failure load is on average increased by 49% compared to pure bolted connection specimens. For the bonded-bolted sleeve connection, a simplified modeling approach is proposed. Based on the continuous damage model and the plastic potential theory, a macroscopic constitutive model in terms of force and displacement is established. This model distills constitutive parameters with clear physical meanings, enabling an accurate consideration of the full-process behavior of the joint in structural-scale calculations at a relatively low computational cost. The phenomenological nature of the macroscopic constitutive model leads to a relatively accurate description of the mechanical behavior of the joint, and the computational cost is small, making it suitable for structural scale calculation analysis of assembled GFRP latticed columns subject to compression loads.