Stress-concentration factors in circular hollow section and square hollow section T-connections: Experiments, finite-element analysis, and formulas

Abstract Nodal T-connections made up of circular hollow section (CHS) braces and square hollow section (SHS) chords (CHS-SHS T-connections) have the advantage that they do not require complex brace end preparation when compared with CHS-CHS T-connections. The stress-concentration factors (SCFs) in CHS-SHS T-connections have also been found to be lower than those in SHS-SHS T-connections by previous researchers. At present, no parametric equations have been developed for determination of SCFs for the design of CHS-SHS T-connections. In this investigation, eight CHS-SHS T-connections with unique nondimensional parameters were strain gauged for determination of strain-concentration factors (SNCFs) and therefore SCFs. A three-dimensional finite-element model was then developed using the ANSYS software to simulate the stress distribution at the brace-chord welded interface under axial force and in-plane bending in the brace. Validation of the model was carried out by comparing the SNCFs determined from the experiment and those determined from the finite-element model. It was found that the finite-element models were able to capture both the maximum SNCF in the connection and the SNCF distribution around the brace-chord welded interface. A parametric study was carried out to determine the SCFs for numerous models with unique nondimensional parameters β (=d1/b0), 2γ (=b0/t0), and τ (=t1/t0). Using multiple regression analysis, equations have been developed for SCFs at hot spots around the CHS-SHS T-connections under the loads axial force in the brace and in-plane bending in the brace. There is good agreement between the maximum SCFs in the CHS-SHS T-connections calculated by the resulting formulas and the maximum experimental SCFs in the connections.