This paper presents an experimental and numerical investigation on the structural response of stainless steel trapezoidally corrugated web girders subjected to patch loading. Four girders were tested to failure, the length and position of the patch load within the corrugation profile were varied to investigate its impact on the ultimate load and failure modes. All four girders were made of lean duplex stainless steel (EN 1.4162/LDX 2101). Initial geometric imperfections were measured using a digital image correlation system. The load-displacement responses and the failure modes were analyzed in detail. In addition, geometrically and materially nonlinear analyses with imperfection included (GMNIA) were also performed. Measured initial imperfections were included in the model. The numerical model was verified against the experimental results. Stress distribution plots were also obtained numerically to further analyze the failure modes and the influence of the strain hardening capacity of stainless steel. Ultimate loads obtained experimentally were also compared with predicted resistances using theoretical models available in the literature. According to the results, neglecting the flange resistance to patch loads according to standard EC3:1–5 leads to a significant underestimation of the capacity of stainless steel and carbon steel corrugated web girders. However, considering the resistance from both the flange and web, the difference between the design model and test results is limited to a safe range of 3–12 % for all four tested girders.