Anti-Blast Performance of Ultra-High Performance Concrete-Filled Double Steel Tubes under Close-in Blast Loading

In order to study the explosion resistance of ultra-high performance concrete-filled double skin steel tubes (UHPCFDST) under near-explosive loads, a three-dimensional finite element model of TNT explosives-UHPCFDST columns-air was established. The ALE multi-material fluid-solid coupling algorithm is used to analyze the damage mechanism, energy absorption characteristics and influence parameters of UHPCFDST columns under near-explosion. The calculation results show that the typical failure modes of UHPCFDST columns under near-explosion are plastic deformation and the collapse of the concrete core pillar. The damage process of the concrete core pillar can be divided into three stages. Compared with the ordinary concrete column, the UHPCFDST column has superior anti-blast performance; within a certain range, reducing the cross-section hollow ratio can effectively improve the explosion resistance of UHPCFDST columns; increasing the thickness of inner and outer steel pipes, particularly for the inner pipe, can increase the explosion resistance of UHPCFDST columns. The presence of axial pressure has a great influence on the deformation of the UHPCFDST column. The increase of axial pressure ratio, within a certain range is beneficial to resisting the overall deformation. As the axial pressure continues to increase, local deformation increases and the UHPCFDST column would lose its strength under the combined effects of the near-blast and the axial loads.