Prevention of concrete breakout failure of expansion anchor in tension by post-installed reinforcement: Discrete analysis and experiment

Concrete breakout failures with acutely damaged concrete are one of the main problems caused by expansion anchors under tensile loading. In this study, the prevention of concrete breakout is investigated by post-installed reinforcement (PRs). Experimental and numerical studies were conducted to look into the effect of the PRs on the expansion anchors subjected to tensile loads. The 3D Rigid Body Spring Model (RBSM), which is based on discrete analysis at the mesoscale, was used as supporting numerical research. On pullout capacity, displacement, failure mechanism, and concrete breakout geometry, both experimental and numerical analyses were undertaken. The numerical analysis also looked at internal stress, strain, and concrete cracking. In general, the anchors with the PRs had steady displacement (ductile) and less brittle failure compared to the anchors without the PRs. The significant finding was in the failure mode, where severe concrete damage and concrete breakout failures were prevented by the PRs. The internal tensile stress of concrete was concentrated around the wedges of the anchors (interlocked area). The contribution of the PRs was shown by high strain values at around their mid-length. Additionally, due to the PRs, concrete cracking was less, mostly generated in the region between an anchor and its PRs. The utilization of PRs could be a method to protect concrete from breakout failure.