Flexural performance of ultra-high-performance concrete beams based on material grading

Four-point bending tests were conducted on nine ultra-high-performance concrete (UHPC) beams with different steel fibre contents and cross-section configurations to investigate the relationship between material tensile performance and member-level flexural behaviour. A material-grading framework was established using strain compatibility between the UHPC and reinforcing bars, direct tensile indices and post-cracking response, and a grade-dependent sectional prediction method was developed for ultimate flexural capacity. The results showed that increasing the steel fibre content delayed first cracking and increased both the cracking load and ultimate capacity, while the cross-section configuration affected post-cracking stiffness and failure characteristics. The proposed method was validated against eight fibre-reinforced beams from the present study and 21 independent specimens from four published studies. For the combined database of 29 specimens, the mean predicted-to-test ratio of ultimate moment was 1.02, with a population standard deviation of 0.07 and an average absolute relative deviation of 5.97%. These results support the proposed linkage between UHPC tensile grading and member-level flexural response, providing a practical basis for grade-dependent sectional capacity prediction.