Plastic behavior of circular steel tubes subjected to low-velocity transverse impact

•Three types of indenters were used to impact steel tubes.•The plastic dent zone of a steel tube was described in detail.•Empirical formulae were proposed for predicting the impact response of steel tubes. This paper presents experimental studies on the plastic behavior of circular steel tubes subjected to transverse low-velocity mass impact. A total of 73 impact tests and 7 quasi-static tests were conducted on the circular steel tubes, which have span lengths of 900, 1200 and 1500 mm. Three representative indenters, i.e., wedge-shaped, hemispherical and cylindrical indenters, were used to impact the specimens, which were fully clamped at both ends by a specially designed clamping system. The impact energy was sufficient to ensure the structural collapse of the tube due to tensile tearing. Both the impact and quasi-static test results showed that the fully clamped steel tube under transverse impact loads involved the three-hinge mechanism to deform. Based on experimental observations, four deflection modes and four failure modes were proposed. Moreover, the plastic dent zones were described in detail. The influences of the geometrical parameters, indenter types and local denting on the magnitudes of the dent zone length and the transverse load were investigated and discussed. Based on the test results, empirical formulae for calculating the length of the plastic dent zone and the transverse load were proposed. These formulae are useful for engineers to evaluate these two values in practice. Good agreement was achieved between the experimental and the predicted results.