Experimental and numerical investigations on the concrete edge failure of anchor groups of arbitrary configurations

Concrete edge failure often governs the failure of anchorages, which are installed close to the concrete edge and are loaded in shear perpendicular towards the edge. The design provisions for concrete edge failure given in the current codes are rather limited in applicability. Only anchorages arranged in a rectangular pattern are allowed. For anchorages without hole clearance, the maximum permissible anchor pattern is with three anchors in a row, and for anchorages with hole clearance, a maximum of only two anchors in a row is allowed. Furthermore, for anchor groups with multiple anchor rows loaded in shear perpendicular to the edge, the failure load may be calculated by assuming the failure crack initiating from the front anchor row (EN1992-4) or by assuming the failure crack initiating from the back anchor row (fib Bulletin 58, ACI 318). No design guidelines exist for non-rectangular anchor configurations. In such cases, the design is based on engineering judgement. In this study, experimental and numerical investigations were performed on anchor groups of triangular and hexagonal configurations to study the concrete edge failure. It was observed that the failure crack always initiates from the back anchor row, even in case of anchor groups, where the first cracking is associated with the first anchor row. The first cracking may have an influence on the displacement behaviour of the group, which might limit the design in SLS. However, this is dependent on the displacement behaviour of individual anchors within the group, edge distance, spacing and hole clearance.