Fiber pullout tests were conducted on more than ninety 10 mm by 10 mm cylindrical concrete specimens with a single, straight steel fiber embedded 10 mm in the center of the concrete specimen. Each specimen was subjected to one of three levels (90 N, 2000 N, 4000 N) of confining force applied by a steel fixture and a servo-hydraulic Instron test frame was used to conduct fiber pullout tests. A previously published fiber pullout model was used to determine the approximate bond strength and frictional stress experienced by the fiber-concrete matrix for each of the three confinement levels. Results show that confinement stresses had a positive correlation with both peak force and work of the pullout force, but the latter was only valid for the first few millimeters of pullout. The correlation with work of pullout disappeared when the entire response was considered. Next an analytical model was used to determine the effects of bond fracture energy and friction. The results of this comparison showed that increased confinement forces caused a measurable increase in frictional stress, but bond energy remained relatively constant. The results of this work can be used to improve future computational model.
McSwain, Arden, "The Confinement Effects on the Fiber Pullout Response of Ultra-High Performance Concrete (UHPC" (2017). Honors College. 274.