Behavior of novel steel-encased beam-end (SEBE) joints for prefabricated prestressed RC braces under cyclic tension

This study proposes a novel steel-encased beam-end (SEBE) K-shaped joint for connecting prefabricated prestressed reinforced concrete (PPRC) braces to concrete-filled steel tube (CFST) columns in a latticed double-column pier system. Focusing on the critical tensile behavior of this joint, an experimental program involving ten half-joint specimens was conducted. The tests investigated the effects of key parameters, including loading protocol, reinforcement ratio, joint configuration, the number of post-tensioned (PT) strands, prestressing level, grouting material, and connection type between the cover plate and the flange plate. Two distinct failure modes were identified: pull-out failure (PF) at the SEBE joint and tensile failure (TF) of the PPRC brace. Experimental results demonstrate that specimens achieving TF exhibited excellent hysteretic performance, stable energy dissipation, and minimal residual displacements throughout the tests. In contrast, PF led to severe strength and stiffness degradation in the later loading stage. The use of steel fiber-reinforced grout (SFRG) and enhanced confinement through plug welding between cover plates and flange plates were found to be effective in preventing PF. The force transfer mechanism within the joint was analyzed and discussed in detail, and a theoretical model for predicting the tensile capacities of the specimens was established, showing good agreement with experimental results. The findings confirm the feasibility and effectiveness of the proposed SEBE joint system for CFST double column-PPRC brace hybrid structures. • A steel-encased beam-end (SEBE) joint is proposed for rigid connection of prefabricated prestressed braces to CFST columns. • Ten cyclic tension tests identify two failure modes and verify the reliability of the SEBE joint. • Steel fiber-reinforced grout and plug-welded cover plates effectively prevent pull-out failure. • A theoretical model is established to predict tensile capacity, showing good agreement with tests.