Abstract: Herein, the impact of the mesoscopic distribution and orientation characteristics of steel fibers in steel fiber-reinforced concrete (SFRC) segments on the macroscopic load-bearing performance are explored. First, a more precise steel fiber placement algorithm grounded in spherical probability density functions is proposed. Then, a three-dimensional fine simulation model of load deformation and damage of SFRC segments is established using MATLAB programming and Abaqus joint simulations. Finally, the mechanical properties and damage evolution of SFRC segments under different parameters are examined in detail by taking the orientation coefficient of steel fiber and the difference rate of fiber distribution as variables. The experimental results show the following: (1) The steel fiber placement algorithm optimized by spherical probability density function effectively solves the problem of uneven placement and significantly improves the prediction accuracy of the model. (2) The orientation coefficient and distribution difference of steel fiber crucially influence the key performance indices such as flexural bearing capacity, resilience, and ductility of segments. When the steel fiber orientation coefficient decreases from 1.0 to 0.3, the flexural resilience of the segment decreases by about 75.79%, and the ductility decreases by about 4.18%. When the distribution difference rate increases from －0.25 to 0.25, the flexural resilience decreases by 26.08%, and the ductility decreases by about 6.72%. In summary, reasonable distribution and orientation of steel fibers are beneficial to safety and stability of the segment structure.

Key words: shield tunnel segments, steel fiber-reinforced concrete, fiber distribution, fiber orientation coefficient, flexural bearing capacity of segment, resilience, ductility