Experimental study into the location of the neutral axis in fiber‐reinforced concrete prisms

Abstract

AbstractThe results of an extensive experimental program into the location of the neutral axis in cracked fiber‐reinforced concrete (FRC) are reported. In total, 74 prisms are tested in a monotonic (51 specimens) and cyclic (23 specimens) bending test in accordance with EN 14651. In the program, 13 different FRCs are considered with 9 different fiber types and dosages. A normal strength concrete with residual strength values between 1b and 2d, cf. Model Code 2010 (MC10), is considered. The deformation profile in the cracked section is measured by side‐mounted linear variable displacement transducers on the prisms, and the position of the neutral axis is calculated. The experimental results are compared against predictions of the MC10. Based on a simplified stress diagram, the MC10 predicts that the location of the neutral axis depends on the residual strength of the FRC at the serviceability limit state: increasing the strength results in a larger compressive zone and vice versa. However, the results obtained within this study do not confirm this relation. The cyclic results indicate that the neutral axis shifts upward during unloading and subsequent reloading decreases the neutral axis again to preunloading levels. Finally, for all reported FRC types, the neutral axis lies very high in the cracked section, even at very small crack mouth opening displacement values.