Rotation capacity of self-compacting steel fiber reinforced concrete

Abstract

Steel fiber reinforced concrete (SFRC) has been used in segmental tunnel linings in the past years. In order to investigate the effect of steel fibers on the rotation capacity of plastic hinges in self-compacting concrete (SCC) the effect of the addition of fibers to SCC in compression, tension and bond was investigated. Based on experiments, the Compressive Damage Zone model was extended to self-compacting steel fiber reinforced concrete (SCSFRC). The effect of the fibers and the load eccentricity was taken into account as a function of the amount of steel fibers, fiber geometry and eccentricity of the load. Due to a varying fiber orientation the tensile properties are direction dependent. They are modeled separately along the bar axis and around the bar. The effect of fibers on the bond behavior has been investigated experimentally and modeled with an analytical bond model based on concrete confinement that takes into account the tensile properties of the concrete. The models were then used as input for the rotation model. The experimental program included four tests on beams loaded at mid-span up to steel or concrete failure. The test variables were fiber content and axial compressive force. In the experiments, the addition of steel fibers in combination with the applied amount of reinforcing bars led to a stiffer behavior, an increase in maximum moment and to cracking but no spalling in the compressive zone. The specimens tested with fibers had a smaller rotation capacity than those tested without fibers, which is explained by localization of the deformations in one large crack in case of the SCSFRC specimens instead of several large cracks in case of the SCC specimens.