Experimental and numerical investigations on tensile failure mechanism and load-bearing capacity of expansion anchors under pull-through failure mode in HPSFRC

Pull-through(PT) is a unique failure mode of torque-controlled expansion(TCE) anchor after being pulled out from concrete. No universal design formula is available for predicting tensile bearing capacity of anchor of PT mode. In normal concrete(NC), PT failure usually occurs at large embedment depths(Hef), which is uncommon in the field and received less attention than the concrete breakout failure. However, due to the improved mechanical performance of the substrate, the PT mode dominates for anchors in high-performance steel fiber reinforced concrete(HPSFRC) substrate (even at small Hef). In this study, to study the PT mode in HPSFRC, the results of 34 PT failures from previous tests, including testing scenarios with different anchor diameters(D), Hef, and fiber contents(vf), are analyzed. The cracking morphology and load-bearing capacity distribution of PT mode are elaborated. Further, finite element models(FEM) of anchor pullout behavior in HPSFRC is established, which accurately identified different failure modes. The calculated Nu by FEM agree well with the tested Nu. The difference in damage domain between different failure modes is mainly reflected in the unloading stage. Parametric analyses were conducted on pre-tightening torque(Tini), Hef, D, sleeve length(Lsleeve), anchor cone width, anchor cone length(Lcone), and vf to study their influences on Nu of PT mode. Except for Lsleeve and Lcone, which do not affect Nu, changes in other factors can cause linear or nonlinear changes in Nu. The non-linear relationship between Nu and experimental parameters is formulated. Accordingly, a new prediction model that can accurately predict Nu of PT mode for anchors in HPSFRC is developed, of which calibration factors are derived using probability functions.