Pull-out behavior and failure mechanism of steel expansion anchors in high-performance steel fiber reinforced concrete(HPSFRC)

Past research on the pull-out performance of anchors mainly focuses on normal concrete(NC) concretes. New design methods are needed for the pull-out performance of anchors in the concretes of new cementitious materials with high strength and toughness. Accordingly, the pull-out behavior of torque-controlled expansion anchor(TCE) in high-performance steel fiber reinforced concrete(HPSFRC) concrete with different fiber content and installation conditions(embedment depth and anchor diameter) was investigated. The focus was on the failure modes, crack morphology, and load-displacement behavior(including pull-out load-bearing capacity, anchorage stiffness, and anchorage toughness). The addition of fibers leads to increased load-bearing capacity and toughness, reduced stiffness, and all failure modes exhibited ductile cracking and sufficient tensile ductility. Both diameter and depth had a positive impact on load-bearing capacity. A broader database based on literature and this study was analyzed for further exploration of the effects of fibers. The accuracy of predicting loadbearing capacity was compared between two empirical models(concrete capacity design-CCD and Toth models) and the proposed modified model. The CCD model greatly underestimates capacity, and the Toth model is unsuitable for high fiber content(exceeds 2.0 %) HPSFRC scenarios. The modified model showed the best bearing capacity prediction for anchors on HPSFRC concretes, with a mean ratio of predicted values to experimental values reaching 1.01-1.08 and a coefficient of dispersion below 15.0 %.