Experimental investigation of concrete breakout strength of anchors in shear within fiber reinforced concrete

Abstract

This study investigates the effects of Polypropylene fibers on the concrete breakout strength of cast in place anchors in shear under different loading rates. The steel headed anchors were cast within concrete specimens of different amounts of Polypropylene fibers. Four differing mixtures were produced using, 0, 0.5, 1, and 1.5% fibers by volume of the mixture. Their physical properties were calculated through testing at the Civil Engineering Laboratory Building. In total, 16 cylindrical specimens, 4” in diameter and 8” in height, and 6 beam specimens, 6”x6”x20” were produced and tested. After 28 days of curing, the specimens were tested for their compressive and tensile strengths, as well as their modulus of rupture. The results of the tests were then analyzed. It was discovered that as the fiber reinforcement approached 1% and over, the compressive strength of the concrete decreased which was attributed to reduce workability and increasing air voids from poor consolidation. In contrast, using Polypropylene fibers leads to increase the concrete tensile strength and the concrete shear breakout capacity for the anchor. Also, it's found that the cone of influence increase as the anchor embedded length or edge distance increase. Cone of influence control the anchor shear mode failure, once the cone of influence is high that leads to steel failure proceeded by concrete spall, for that mode of failure increasing fiber dosage 1.0% leads to decrease load failure 55% and decrease displacement 50%. Loading rate will play a major roll to determine the failure load, once the loading rate is higher that will provide a higher impact load, where increasing loading rate 150% leads to decrease load failure 25% and increase displacement 15%.