Anchorage of reinforcement in concrete corners: Experiments and refined measurements

The anchorage of reinforcement in concrete is a complex phenomenon typically governed by several failure modes, including: pull-out failure, splitting, side spalling, edge wedge spalling, and corner spalling, depending on multiple factors. Extensive research has focused on the first four failure modes, however there is little detailed information in the literature regarding corner spalling. This paper presents an investigation aimed at better understanding the mechanical response and performance of anchorages in concrete corners. The investigation involves a series of inner-pressure tests performed with hydraulic inflator devices in cylindrical openings and pull-out tests on anchorages positioned near the corner. The effects of parameters commonly adopted in engineering practice are investigated, including concrete cover, casting position, confinement index, and anchorage length. Through detailed measurements, insights into the local and global behaviour, resistance, and failure mechanisms of corner anchorages are gained and thoroughly discussed. The results are further compared with the response of edge anchorages which failed due to wedge spalling, demonstrating that the effect of the casting position is less significant for corner anchorages than that for edge anchorages, as the inclined cracking plane caused by pressure does not align with sub-horizontal settlement cracks. Additionally, corner anchorages exhibit smaller resistances than edge anchorages with similar covers and lengths, due to limited stress redistribution capacity and more brittle behavior. On that basis, a mechanical model for calculating the corner spalling resistance is developed and validated, showing consistent agreement with the experimental results, which can be regarded as a step forward in the development of a unified mechanical model for anchorages that fail in different modes. This study underscores that Eurocode 2 (FprEN 1992–1–1:2023) tends to provide unconservative predictions for corner anchorages.