Free-spanning and base-supported tubes subjected to combined axial compression and indentation loads

Abstract Much research has been conducted on circular hollow steel tubes subjected to indentation loads, but the response of a circular hollow steel tube when subjected to a combination of an indentation load (the load applied by an indenter) acting together with other loading conditions has received markedly less appraisal. An experimental study was conducted on two groups of circular hollow steel tubes that were either free-spanning or were base-supported. These tubes were first subjected to a uniform axial pre-compression, which is the most common service load across many tube applications, followed by the application of indentation loads while the magnitude of axial pre-compression was maintained. Strength, top surface and mid-height cross-sectional deformation, longitudinal and circumferential strains, and the failure mechanism of the tubes were compared, with a significant difference found between the response of the two groups of tests, and with this difference increasing as the magnitude of axial pre-compression and indenter displacement were increased. Additionally, it was identified that for the same level of absorbed energy, a deeper dent was produced for base-supported tubes than for free-spanning specimens. Moreover, analytical equations available in the literature were compared to the experimental results and good correlation was found between the experiments and the predictions.