Experimental and numerical investigation of flexural behavior of precast tunnel segments with hybrid reinforcement

Precast concrete segments reinforced with a combination of steel fibers and conventional rebar (RC-SFRC) have gained prominence in the mechanized construction of tunnels in recent years due to the advantages offered by this hybrid reinforcement solution in enhancing the mechanical behavior of these structural members. This research aims to understand better the flexural behavior of RC-SFRC tunnel segments proposed to replace conventional reinforcement in S & atilde;o Paulo Metro Line 5. An experimental program and numerical analyses using a multiscale model were conducted to predict the post-cracking parameters of SFRC through three-point bending tests according to EN14651 and assess the flexural behavior of full-scale tunnel segments. In both scenarios, 2D multiscale numerical models with discrete and explicit representations of the reinforcements were applied. The comparison of numerical and experimental results in terms of crack width, mean crack spacing, deflection, and the ultimate and service loads derived from design predictions demonstrate that the proposed RC-SFRC reinforcement represents an advantageous alternative, significantly enhancing the performance of the segments for both serviceability and ultimate limit states. Furthermore, the responses show that the adopted numerical strategy is promising and can be consolidated as a tool for optimizing the design process.