Experimental assessment of stiffening geometries for thin-walled structural steel plates made by wire arc additive manufacturing

• Piloting sinusoidal stiffening for WAAM parts, with strength increase by 9-30%. • Validating with SHS/I-section tests, showing higher capacity via delayed buckling. • Proposes code improvements counteracting WAAM's manufacturing defects. • Solves WAAM limitations (uniform thickness, thin walls) for safer large-scale use. An innovative strategy of imposing geometric sinusoidal waves has been proven effective in enhancing the local buckling resistance of steel plates made by selective laser melting (SLM). However, its efficiency on wire arc additively manufactured (WAAM) steel, which is a more economically and environmentally viable alternative, remains unexplored, particularly given the manufacturing defects such as material anisotropy and geometric inaccuracy associated with WAAM. This work presents an experimental investigation into the stiffening effect of sinusoidal wave patterns on WAAM-fabricated steel plated sections. Stub column tests and geometric measurements were conducted on square hollow sections (SHS) and I-sections fabricated in 316L stainless steel. The specimens incorporated the sinusoidal wavy geometries previously validated in equal-leg angle sections under external plate boundary conditions. The present study extends their application to internal plate elements in SHS stub columns and examines the combined behaviour of internal and outstanding plate elements in I-sections with sinusoidal stiffening. The obtained results demonstrate a normalised strength enhancement of up to 9% with equal or even less material consumption (0.2% to -4.5%). Comparisons are made with conventionally manufactured and existing WAAM-fabricated stainless steel plated elements, as well as with current Eurocode 3 design equations and provisional design rules proposed for SLM-fabricated stiffened plates. Based on the findings, design recommendations for such structures have been made.