Low cycle fatigue and monotonic performance of double-skin composite members with through-depth shear connectors

This study experimentally investigates the shear performance of double-skin composite (DSC) structures incorporating innovative through-depth shear connectors. Eight push-out tests were conducted to evaluate structural behavior under monotonic and low-cycle fatigue loading. Key parameters included the composite system configuration and connector design-specifically welded, snug-tightened, and traditional headed studs. Results demonstrated that welded through-depth connectors achieved the highest ultimate capacity, reaching 803.17kN under cyclic loading, showing 31.4% strength advantage over snug-tightened counterparts. Furthermore, the snug-tightened systems exhibited a 468% higher post peak endurance, suggesting a superior stress redistribution. However, failure across all specimens was characterized by concrete crushing and diagonal cracking rather than connector shear fracture. Notably, the DSC configuration provided only a marginal 2% capacity increase over standard designs when using headed studs. Comparative analysis revealed that Eurocode 4 equations overestimate shear capacity by 19–21%, as they fail to adequately account for concrete confinement and specific failure modes. These findings suggest that accurately evaluating DSC systems requires balancing in high stiffness of welded connectors 41.23kN/mm against the exceptional ductility of snug-tightened and headed stud configuration.