Pullout behavior of inclined steel fiber in an ultra-high strength cementitious matrix

In this study, as a part of research to characterize the tensile properties of steel fiber reinforced ultra-high strength cementitious composites, pullout tests of steel fiber were performed to evaluate the effect of fiber inclination angle on the load direction and an analytical pullout model was derived considering this effect. The fiber inclination angles considered in the pullout tests were 0°, 15°, 30°, 45°, and 60°. From the pullout tests, it was observed that the largest peak load was obtained at an angle of 30° or 45°, and the peak slip increased as the fibers were oriented at a more inclined angle. Based on the experimental results, an analytical pullout behavior model considering fiber inclination was proposed. In order to take into account the effect of fiber inclination in the pullout model, apparent shear strengths (τ(app)) and slip coefficient (β) were introduced to express the variation of pullout peak load and the augmentation of peak slip as the inclined angle increases. These variables are expressed as functions of the inclined angle (ϕ).