Seismic performance of assembly joints between HSPC beams and concrete-encased CFST columns

Abstract

In this study, an assembly joint between a hybrid H-steel precast concrete (HSPC) beam and concrete-encased concrete-filled steel tubular (CFST) column was developed for precast composite structures. The HSPC beam was designed with a novel configuration to connect to the concrete-encased CFST column through a cantilever H-steel beam. To investigate the effectiveness of the developed joint, reversed cyclic load tests were conducted on three full-scale exterior subassemblies with different types of cantilever beams: original, reduced beam section (RBS) and opening in beam web (OBW). The seismic performance of the developed joints was analysed comprehensively based on the failure pattern, hysteresis curve, stiffness degradation, ductility, and dissipated energy. The specimen with the RBS steel beam exhibited a stable hysteretic behaviour up to 4.75% of drift ratio and remarkable ductility, and the cumulative dissipated energy was up to 8.8 times that of the original specimen. However, the improvement in the specimen with the OBW steel beam was insignificant compared with that in the original specimen. Hence, the developed joint with the RBS steel beam exhibited more satisfactory seismic behaviour in terms of the capability to relocate the plastic hinge to the required. This could be applicable in high seismic zones. The seismic performance of the developed joints was affected significantly by a reduction in the reinforcement ratio of the bars transferring the bending stress between the H-steel and RC beams. Therefore, simplified formulas for ensuring a sufficient reinforcement ratio of the bars were proposed and validated through tests.