Back-calculation of mechanical properties of fiber-reinforced concrete in tunnel lining segments

Precast segmental tunnel linings (PSTLs) are critical components of tunnel construction and provide immediate support and long-term durability. Steel fiber-reinforced concrete (SFRC) has become a preferred choice for PSTLs due to its economic advantage, enhanced ductility, and durability. This study analyzed flexural load-deflection results of over 1000 SFRC samples from the South Hartford Conveyance and Storage Tunnel project using ASTM C1609 tests. Using a strain compatibility analysis of a parameterized quad-linear model of tensile and compressive properties, an inverse analysis procedure was conducted and compared with the conventional linear elastic assumptions. It is shown that proper characterization reduces the variability of flexural parameters and underscores the importance of residual strength properties on the stress distribution in sections. Using four different methods to obtain the constitutive response of the individual samples from the population data, a procedure that involves the moment-curvature response, neutral axis location, and internal force computations is used as a framework for the analysis and design of FRC in flexure. It is shown that the average residual tensile strength that satisfies the strain compatibility and constitutive response is the basis for an equivalent tensile force and internal moment. Equations for the correlation of the present approach with experimentally obtained nominal flexural strength are proposed.