Experimental and numerical study on damage mechanism of CFDST bridge columns subjected to contact explosion

The blast performances of concrete-filled double-skin steel tube (CFDST) columns subjected to contact explosion were investigated experimentally and numerically in the present study. Field tests were carried out on three circular CFDST column specimens under contact explosion, and different damage modes were observed from the tests. Arbitrary-Lagrangian-Eulerian (ALE) formulations coupled with Fluid-Structure Interaction (FSI) algorithms that are available in the explicit nonlinear dynamic analysis program LS-DYNA were utilized to develop the numerical models. The feasibility and accuracy of the numerical models were verified against the experimental results. After that, the numerical models were used to further investigate the dynamic response, damage evolution, and energy absorption mechanism of CFDST columns subjected to contact explosion. The results indicate that CFDST columns under contact explosion are likely to suffer a localized damage while exhibits almost no global responses. The localized damage concentrates in the vicinity of the detonation zone, including cratering around the detonation point, fracture or rupture failure of the outer steel tube, and breaching failure in the front sandwich wall. The core concrete failure plays a dominant role in the energy absorbing mechanism of CFDST columns owing to the confinement effect provided by the steel tubes. In addition, the presence of the outer steel tube can effectively prevent the concrete spall damage thus mitigating the potential damage to personnel and equipment caused by ejected fragments.