Impact of Undercut and Lack of Penetration on the Design Static Resistance of Butt‐Welded Connections

Abstract

The fabrication and construction of steel structures within Europe are governed by the quality, execution, and control requirements outlined in EN 1090‐2. For welded connections under static loading, Eurocode 3 refers to the quality level C set out in ISO 5817. However, this specification is not explicitly supported by scientific evidence. To address this gap, experimental tests were performed on butt‐welded connections containing undercut and lack of penetration, with the objective to assess their influence on the load‐bearing capacity. The results highlighted that undercuts within quality level D had no measurable effect, whereas lack of penetration below quality level D led, in some cases, to a resistance reduction. To extend the analysis, finite element models of the specimens were developed in ANSYS using the Gurson model. A parametric study was then performed, varying imperfection dimensions, plate thicknesses, and material properties. The results indicated that butt‐welded connections with imperfections at or below quality level D still achieved adequate resistance. This resistance exceeded the design resistance defined in Eurocode 3 for butt‐welded connections. Finally, a statistical evaluation of partial safety factors was conducted for each imperfection type. Revised limits for undercut and lack of penetration for an evaluation of the static resistance according to Eurocode 3 part 1‐8 are thus proposed.