Analytical Analysis of Whole Loading Process of Ultra-High-Performance Fiber-Reinforced Concrete Beams in Flexure

The mechanical and durability properties of ultra-high-performance fiber-reinforced concrete (UHPFRC) are superior to conventional concrete. However, the available stress-strain models of UHPFRC are relatively complicated and cannot be applied to the analytical analysis of loaded beams for the ultimate and serviceability limit states. In this paper, a piecewise linear axial stress-strain relationship is proposed. The stress-strain relationship is further simplified as a rectangular stress block, and the stress of concrete during the whole loading process is accordingly evaluated. The development of the beam hinge at the midspan is described in detail, and it is then incorporated into the concrete stress blocks to derive an analytical approach and a closed-form solution for modeling the whole loading process of UHPFRC beams. Through comparisons with experimental results collected from the literature, it is validated that the proposed approaches can reasonably predict the whole loading process, including the ultimate strength, flexural rigidity, and ductility of UHPFRC beams, which only require material properties without any experimental calibration.