Local buckling of hollow steel box columns under the combined action of axial load and internal lateral pressure

An innovative scheme and a test device for applying internal lateral pressure for the steel tube was proposed. Then the local buckling of hollow steel box columns under the combined action of axial load and internal lateral pressure was studied in laboratory experiments. The effects of internal lateral pressure on local buckling, strain development and the columns’ ultimate bearing capacity were documented. Internal lateral pressure was found to promote local buckling and impair a column’s ultimate strength. Digital image correlation (DIC) measurements demonstrated that the start of local buckling cannot reliably be observed with the naked eye. Doing so leads to overestimation of the local buckling strength by about 10%. Finally, the discriminating criteria of local buckling is explored, which can solve the problem that the local buckling cannot be identified timely by observation.