Experimental study on the mechanical behaviour of eccentric compression short column strengthened by ultra-high-performance fibre-reinforced concrete

Abstract

Ultra-high-performance fibre-reinforced concrete (UHPFRC) has been widely adopted in the strengthening of reinforced concrete (RC) beams and slabs due to its excellent mechanical properties and durability. Although many studies have been conducted on the mechanical behaviours of RC structures reinforced by UHPFRC, the mechanical behaviours of UHPFRC-reinforced RC structures in a combined force state of bending and axial compression remain unknown. In this study, an eccentric compression short RC column, which was strengthened by a UHPFRC layer on the tension/compression side, was studied based on experiments and numerical simulations. Some key performance attributes of the short columns including load carrying capacity, stiffness, ductility, strain, cracking, and lateral deflection were investigated. In addition, finite element (FE) models were established to determine the influence of the reinforcement parameters including the reinforcement ratio and the thickness of the UHPFRC layer as well as the reinforcement location. The results showed that the UHPFRC layer could significantly increase the load carrying capacity and the stiffness while reducing the ductility of the short RC columns. In addition, the UHPFRC layer could delay the formation of cracks and control their development. The results also showed that the RC columns bonded well with the UHPFRC layers. No bond failure but partial bond slip occurred at the interface. Furthermore, the unreinforced UHPFRC layer could still effectively promote the load carrying capacity of the short RC columns, either reinforced on the tension or compression side. The improvement rate obviously increased with increasing thickness of the unreinforced UHPFRC layer.