Experimental and simulation study of the flexural performance of steel–HFRC composite box girder

Hybrid-fibre-reinforced concrete (HFRC) utilises the bridging effect of high-toughness fibres to enhance the brittle failure of concrete materials, limit the generation and development of cracks, and significantly improve deformation capacity. In this work, the flexural behaviour of a steel–HFRC composite box girder was systematically investigated through static loading tests. The results showed that the steel–HFRC composite box girder exhibited excellent crack resistance and flexural performance under static loading conditions. Furthermore, a separation modelling approach, incorporating Python subroutines, was used to establish a non-linear finite-element model using Abaqus software. Simulations showed that the shear connection degree significantly impacted the flexural rigidity of the composite beams. The use of hybrid fibres (steel fibres (SFs) and polypropylene fibres) effectively restricted the propagation of cracks. When the SF volume fraction was increased from 0 to 0.6%, the ductility factor and the ultimate flexural moment of the composite beams increased by about 9% and 3%, respectively. Theoretical formulas were established to calculate the flexural capacity of the steel–HFRC composite box girder, considering the slip effect. Compared with the traditional normative calculation method, the formula for calculating the flexural capacity of composite beams considering slip and SF represents a competitive numerical method that can be used to evaluate the flexural capacity of structures.