Experimental and design‐oriented research on fiber reinforced concrete segmental tunnel linings: A systematic review

Abstract The use of fiber reinforced concrete (FRC) in precast tunnel segments is among the most established and representative applications of this material. Over the past two decades, numerous tunnel linings were constructed with partial or total substitution of conventional steel reinforcement by fibers, this yielding to quantifiable benefits in both technical and sustainability performances. Research on this field is focused on: (1) reliably quantifying and optimizing the mechanical properties of FRC; (2) assessing structural response of FRC segments under normal stresses (caused by flexure with/out concomitant axial loads) and/or concentrated loads; (3) the effect of elevated operational temperatures and accidental fire actions on the mechanical performance of FRC segments (de‐ and coupling service loads); (4) examining the synergistic effect of FRC with other reinforcement systems (e.g., conventionally reinforced concrete, RC; glass fiber reinforced polymer, GFRP); and (5) evaluating the sustainability performance of FRC and RC + FRC (R/FRC) solutions. In view of the extensive research carried out and published literature, this paper presents a systematic and transparent review of the literature on FRC precast tunnel segments, encompassing both experimental and design‐oriented contributions. To this purpose, the experimental evidences are synthesized to report material characterization and full‐scale testing outcomes, while the design‐oriented contributions are examined with emphasis on analytical, numerical, and finite element models capable of reliably predicting structural behavior. The review indicates that, depending on geometry and design actions, FRC can partially or fully replace conventional reinforcement, with advantages especially in terms of serviceability requirements; validated models provide accurate response predictions and clarify the influence of key parameters (e.g., residual flexural tensile strengths, reinforcement ratio, load eccentricities, imperfect contacts, among others). The study concludes with recommendations for future research to support code development. The findings are intended to encourage and support designers and practitioners in considering FRC and/or R/FRC solutions as viable alternatives for segmental tunnel linings.