Corrosion effects on shear resistance and fatigue behavior of self-piercing riveted cold-formed steel connections

Cold-formed thin-walled steel structures are increasingly adopted in modern construction, yet their safety is governed by the reliability of the connections, which are frequently exposed to aggressive environments and earthquake- or service-induced cyclic deformations. Self-piercing riveting (SPR) has emerged as an efficient, automated joining technique, but its performance under a corrosion environment remains poorly understood. To address these gaps, this study investigates the effects of corrosion on the shear resistance and fatigue behavior of SPR connections in cold-formed steel sheets. Accelerated corrosion tests are first conducted to obtain specimens with different corrosion levels. Subsequently, monotonic shear tests and fatigue tests are performed to evaluate the degradation of mechanical properties and fatigue performance. The failure modes, load-displacement responses, and fatigue lives are systematically analyzed. The results show that after 90 days of corrosion, the shear capacity decreased by 15.3%-35.6% depending on the joint geometry, and the fatigue life decreased by 17.6%-39.0% depending on the load level. Furthermore, an interpretable machine-learning framework based on XGBoost with SHAP (SHapley Additive exPlanations) analysis is adopted to quantify the contribution of each corrosion and geometric factor to the capacity degradation, thereby revealing the dominant mechanisms of shear- and fatigue-resistance loss. The findings of this study provide new insights into the corrosion-induced degradation mechanisms of SPR connections and contribute to the development of more reliable design methods for cold-formed steel structures in aggressive environments.