Tensile behavior and failure modes of expansion anchors in High-Performance Steel Fiber Reinforced Concrete (HPSFRC)

To investigate the tensile(pullout) behavior of expansion anchors in High-Performance Steel Fiber Reinforced Concrete(HPSFRC), 30 valid unconfined tension(pullout) tests on expansion anchors, studying the effects of different steel fiber content(0.0 %, 0.5 %, 1.0 %, and 1.5 %), embedment depths(25 mm, 35 mm, and 45 mm), and anchor diameters(10 mm and 12 mm) on the tensile behavior of anchors. A total of seven failure modes, including different types of mixed modes, are observed. The incorporation of fibers reduces the anchorage stiffness, increases the ductility, and improves the post-peak performance of the tensile behavior of anchors. Effective embedment depth(Hef)exerts a great influence on the failure mode; as Hef increases, the dominant failure mode transits from the concrete breakout to the pull-through and mixed failure modes, and finally the steel failure mode. The increase in Hef also leads to increases in the ultimate tensile strength of the anchor(Nu) and the anchorage ductile. For the same Hef and fiber content, compared to the smaller diameter(D), Nu for the larger diameter is larger but the pullout ductility is weaker. A modified model considering the influence of steel fibers is proposed to predict Nu of CB mode in HPSFRC, and it results in more accurate predictions compared to the existing prediction models(CCD model, Toth model). An existing prediction model for PT mode in normal concrete has been proven to be applicable for anchors HPC/HPSFRC.