Study on the flexural performance and deflection calculation method of UHPC-NC hybrid beams with different parameters

Abstract

Based on the excellent mechanical properties of ultra high performance concrete (UHPC) such as high strength and good toughness, this study proposed an ultra high performance concrete-normal concrete (UHPC-NC) hybrid beams, in which UHPC was used to replace part of the NC in the tension or compression zone along the beams. The flexural behavior of 4 UHPC-NC hybrid beams and 2 control beams at different UHPC height was investigated. Based on the flexural experiments of UHPC-NC hybrid beam, a finite element model was established using ABAQUS to investigate the effects of UHPC height, reinforcement ratio, NC compressive strength and UHPC tensile strength on the flexural behavior of the hybrid beams. In addition, the differences in flexural performance and force mechanisms between the hybrid beams and the control beams were compared. Finally, based on the immediate stiffness and effective cross-sectional moment of inertia of the hybrid beams, a model for the mid-span deflection calculation of the UHPC-NC hybrid beam at a reasonable UHPC height was proposed. The results show that the load carrying capacity, energy absorption capacity and stiffness of the hybrid beams increase with the UHPC height, while the ductility initially increases and then decreases. The UHPC height has a significant effect on the flexural performance of UHPC-NC hybrid beams. The reinforcement ratio has positively improved the load carrying capacity of the hybrid beams, although specimens with larger reinforcement ratios exhibit lower ductility. The mid-span deflection calculation model for UHPC-NC hybrid beams was proposed in this paper is in good agreement with the existing experimental results, the calculation process of the calculation model is relatively simple and can provide a theoretical basis for engineering design.