Prediction of the compressive strength of welded RHS columns undergoing buckling interaction

• Compression tests of welded RHS columns with buckling interaction were conducted.
• Strength formulae in the Direct Strength Method for RHS columns were proposed.
• The formulae can account for interaction of local buckling and overall buckling.
• The proposed strength curve was proven reliable in comparison with test results of welded RHS columns.

This paper describes a series of compression tests performed on welded rectangular hollow section (RHS) columns fabricated from 6.0-mm-thick steel plates with a nominal yield stress of 315 MPa. The ultimate strength and performance of the welded RHS compression members undergoing a nonlinear interaction between local buckling and overall buckling were investigated experimentally and theoretically. The compression test results indicated that the interaction between local buckling and overall buckling had a significant negative effect on the ultimate strength of the welded RHS columns. Design strength formulae for the direct strength method (DSM) for the welded RHS columns were proposed based on the compression test results. The study results confirmed that DSM based on the American Institute of Steel Construction (AISC) or Eurocode 3 (EC3) column curves can properly predict the ultimate strength of welded RHS columns when local buckling and overall buckling occur simultaneously or nearly simultaneously.