Strain and stress concentration of completely overlapped tubular CHS joints under basic loadings

A completely overlapped tubular circular hollow section (CHS) joint specimen is tested under lap brace axial loading (AX), in-plane (IPB) and out-of-plane bending (OPB) to determine the strain concentration factor (SNCF) at the intersection of members for the verification of a finite element (FE) model. The experimental results showed that the strain distribution on the outer surface of members near the weld toe of the joint is fairly linear. The maximum SNCF of the joint occurs at the through brace saddle near the lap brace under AX and OPB and at the lap brace crown heel under IPB. The SNCF at the intersection of the chord and through brace for the joint under IPB and OPB is negligible. For the FE analysis, the comparison of SNCF between the test specimen and the 8-node thick shell FE model under AX, IPB and OPB load cases shows reasonably good agreement with average differences of 7.9%, 10.6% and 5.8% respectively. The comparison of stress concentration factor (SCF) revealed that the existing T/Y-joint equations are not suitable for predicting the SCF of completely overlapped tubular CHS joints. The SCF of completely overlapped tubular CHS joints can effectively be reduced by proper control of its geometrical properties.