Behaviour of polymer-filled–concrete–steel double-skin tubular columns under combined lateral impact and axial compression loading

The paper presents a study on the suitability of using a Polymer as a protective layer for critical structural elements prone to impact damage. Conventional damage mitigation methods include using an outer steel jacket with a void, protecting the inner concrete-steel composite column. Whilst it is usually found that the outer steel jacket can partially negate the impact load, the inner column still experiences a significant brunt of the impact load. In order to minimise the damage to the overall critical structural element, a concept of a Polyurethane Polymer-Filled–Concrete–Steel Double-Skin Tubular Column is proposed. Scaled-down versions of two polymer-filled double-skin column configurations were tested under low-velocity impact using a drop tower. The pre and post-damage columns were tested for their axial capacities. These polymer-filled columns were critically compared to their nominal samples without the Polyurethane fill. It was shown that the mid-span deflection and localised indentations were reduced by 17%, and the localised deformations (at the point of impact) were reduced by up to 70% overall. The columns with Polyurethane also showcased retention of 70% of axial capacity post-impact, whilst the nominal sample was only capable of retaining 48%. Finally, the intrinsic properties of Polyurethane were discussed along with a critical discussion on its ability and mechanism on how energy is dissipated by comparing mechanical and chemical properties.