Axially pre-loaded steel tubes subjected to lateral impacts (a numerical simulation)

The behaviour of axially pre-loaded steel tubes subjected to lateral impacts was already studied experimentally by the authors. One metre long tubes were first axially compressed and then impacted at their mid-span using a dropped object moving with a velocity of about 7 m/s. This paper reports details and results from a numerical attempt to simulate those impact experiments. A non-linear finite element implicit time domain dynamic approach has been used for the simulation. The numerical models employed have been found to efficiently simulate the failure sequences in the tubes which were subjected to a dynamic instability. In tubes which did not fail during the impact tests, the first impact and its subsequent rebounds have been properly simulated. Different numerical outputs such as the natural frequency of vibration in the intact and impacted tubes, failure loads and time histories of the impact load, the axial load and the tube deformations have been correlated against corresponding experimental records. In general, a good level of agreement has been noticed between the numerical and experimental results. Effects from parameters such as structural damping, variations in the pre-loading, etc. on the response of the impacted members have also been studied.