Experimental study on seismic performance of precast LSECC/RC composite joints with U-shaped LSECC beam shells

Abstract

Precast beam-column joints are key components of precast reinforced concrete (RC) frame structures. The complex reinforcement details in the joint zone due to high seismic demand have made the prefabrication and construction process in regions with high earthquake intensity difficult to perform. As a type of high-performance fiber-reinforced cementitious composites (HPFRCCs), low-shrinkage engineered cementitious composite (LSECC) exhibits stable strain hardening and multiple cracking properties with a dry shrinkage even lower than that of normal concrete. A partial substitution of concrete with LSECC can significantly improve the seismic performance and damage tolerance of beam-column joints and help simplify the reinforcement details in the joint zone. This paper proposes a novel precast LSECC/RC composite beam-column joint using U-shaped precast LSECC beam shells. Five interior beam-column sub-assemblages were tested under cyclic loading, including one monolithic and four precast specimens. Parameters including lap splice length, transverse and longitudinal reinforcement ratios were studied. The proposed construction process was proven to be both easy and fast. The performance of the precast joints were evaluated in terms of the ultimate capacity, deformation, energy dissipation, shear distortion and strength of the joint core. The test results showed that the proposed joints could effectively simplify the joint reinforcement details while maintaining the required seismic performance. The diagonal cracks in the joint zone without transverse reinforcement were well controlled. A few stirrups in the joint zone could reduce the shear deformation and improve the energy dissipation capacity. The shear strength of the LSECC joints without any transverse reinforcement were found to be similar to the nominal shear strength of well-confined normal concrete joints suggested by ACI 318-14.