AbstractThe effects of hidden toe welds on the static behavior and strength of rectangular hollow sections to rectangular hollow sections (RHS-to-RHS) overlapped K-connections is investigated. Five full-scale welded specimens with a high overlap ratio were fabricated and tested under quasistatic loading in a universal testing machine, with the existence of hidden toe welds and branch loading condition varied. The experimental results were used to validate corresponding numerical models, and a parametric study was performed thereafter. The experimental and numerical results indicate that the overlapped K-connection capacity is affected by the presence of a hidden toe weld and the branch load case but remains within a reasonable range of the capacity predicted by certain codes and guides. Considering all the branch load cases studied, the hidden toe in a partially overlapped K-connection can be left unwelded, while some modifications are suggested to current design recommendations to account for this. A new method for calculating the branch local failure limit state is proposed, which can be used to accurately predict the capacity of overlapped RHS K-connections, without considering hidden toe welds in partially overlapped K-connections.