The Shared-Volume Anchorage Method

A volume-based treatment of anchor groups at concrete corners and in three-sided channel connections, where two anchorages compete for the same failure body and EN 1992-4 offers no clause

Abstract

EN 1992-4:2018 verifies a fastening on one concrete face. It has no provision for the case in which two anchor plates sit on perpendicular faces of the same corner, nor for a channel section that wraps a member on three sides. Both are ordinary in façade and precast practice. Designers are left with two poor options: superpose the two anchorages, which counts the same concrete twice, or verify each in isolation and discard the interaction, which is uneconomic and still not a proof.

This paper sets out the method used in AAS for these two configurations. Its central idea is that competition between anchorages is a question of volume, not of area: each potential failure body is integrated numerically over the concrete, and the fraction of a body that is neither shared with a stronger neighbour nor outside the member becomes a scalar reduction factor r. The stronger anchorage — the leading face — is then verified at its full, unmodified EN 1992-4 resistance; the weaker one contributes a secondary term reduced by r and by a non-simultaneity factor. The construction is deliberately degenerate: as the corner interaction vanishes, r → 1 and the result reduces identically to a plain EN 1992-4 verification.

The method is an engineering design aid, not a code-verified resistance, and this paper states its open assumptions as plainly as its results. No experimental programme is claimed: the evidence offered is internal — exact degeneracy to EN 1992-4 in the limit, dimensional and symmetry consistency, and agreement with independent EN-based software on every quantity the two have in common.