Study on the influence of section dimensions on the shear performance of RC beam with UHPC formwork

Abstract

Using ABAQUS software, a finite element analysis model is established to investigate the shear failure of reinforced concrete (RC) composed beams without stirrups using ultra-high performance concrete (UHPC) permanent formworks. The model accounts for the influence of steel fibers and the interaction between UHPC formwork and normal concrete on the shear performance. Based on the validation of the accuracy of the finite element model, the effects of section height, shear span ratio, and UHPC formwork thickness on the shear capacity, shear ductility, and nominal shear strength of the beams are studied. Additionally, the shear capacity gains of RC beam with UHPC formwork are compared to those of conventional RC beams. Finally, based on the simplified modified compression field theory (MCFT) and the truss-arch model, a method for calculating the shear capacity of RC beam with UHPC formwork is proposed. The research results indicate that the shear capacity of the beam increases with the increase in UHPC formwork thickness and section height, while it decreases with the increase in the shear span ratio. Shear ductility and nominal shear strength exhibit significant size effects. As the section height increases, both shear ductility and nominal shear strength decrease significantly. Increasing the shear span ratio and reducing the UHPC formwork thickness can mitigate the size effect of nominal shear strength. Compared to conventional RC beams, RC beams with UHPC formwork exhibit significantly higher shear capacity. However, as the section height increases, the gain in shear capacity gradually decreases. Finally, the proposed shear capacity calculation method shows good agreement with experimental values. The calculation process is relatively simple and can be used for engineering design