Seismic performance of HSS reinforced interior beam-column joints with high-strength steel fiber concrete and enhanced reinforcements

Abstract

Reinforced concrete moment frame structures in high seismicity regions were often faced with complicated reinforcement details in the joint resulting in construction difficulty. High-strength steel (HSS) bars were used as longitudinal reinforcements in beams and columns to reduce the bar amount and alleviate steel congestion. High-strength steel fiber concrete (HSSFC) was adopted in the joint to enhance the bonding performance of HSS bars. Meanwhile, an enhanced detail of X-shaped reinforcement was proposed to enhance the shear strength. This study investigated the effect of adopting a hybrid method, including HSSFC and X-shaped enhanced reinforcement, on the seismic behavior of interior beam-column joints (BCJs) with HSS bars. Eight full-scale HSS-reinforced interior BCJs were tested under reversed cyclic loading to examine the seismic performance and evaluate the influences of enhanced reinforcement, shear compression ratio, and HSSFC usage. Seismic performance was evaluated in terms of cracking patterns, loading capacity, energy dissipation, and ductility. Test results showed that HSS-reinforced interior beam-column joints with HSSFC exhibited excellent seismic performance with less concrete damage, enhanced ductility, and increased energy dissipation capacity. Similar results were achieved for HSS-reinforced BCJs with X-shaped enhanced reinforcements. Moreover, slippage of beam longitudinal reinforcements and shear deformation were also decreased due to improved bond performance between HSS bars and HSSFC, resulting in less occurrence of bond-slip at the beam end. A suggested equation was proposed for regulating the diameter of high-strength beam bars through the joint section and the height of the column section.