Seismic behaviour of precast BFRP-reinforced concrete beam–column joints in sea-sand concrete

To investigate the seismic behaviour of precast seawater sea-sand concrete beam–column joints with basalt-fibre-reinforced polymer (BFRP) bars, four specimens were tested, including cast-in-situ (CiS) and precast interior/exterior joints. All specimens failed in flexure at beam ends near the column, satisfying the ‘strong joint–weak member’ principle. The CiS interior joints showed higher capacity and stiffness than precast ones, while precast joints exhibited better strength stability and cumulative energy. For exterior joints, the capacity differences were minor; the CiS specimens had 10.3–38.4% higher stiffness, but the precast exterior joints showed better strength stability and energy dissipation, with a 19.1% improvement in energy dissipation, meeting the ‘equivalent to CiS’ requirement. An OpenSees finite-element model effectively simulated the load-bearing behaviour. Parameter analysis indicated that increasing the axial compression ratio, concrete strength, number of U-shaped BFRP bars and beam tensile reinforcement area enhanced the capacity. Notably, the number of beam tensile reinforcements and U-shaped BFRP bars had a greater influence on capacity than the axial compression ratio and concrete strength.