###### Abstract  
Reactive powder concrete-filled steel tube (RPC-FST) is a critical supporting component of large-span, high-rise, and heavy-load structures. The collapse of RPC-FST may occur under explosive load. Therefore, investigation of the dynamic response is essential for understanding the mechanisms of collapse. In this article, the numerical simulation of reactive powder concrete (RPC) adopted the modified Holmquist-Johnson-Cook (HJC) model and the modified Karagozian and Case (K&C) model. The dynamic response of RPC-FST columns under explosive load is analyzed based on arbitrary Lagrange-Euler (ALE) method. The proposed model is verified by experimental results. Results show that the modified HJC model and modified K&C model can be applied to simulate the dynamic response of RPC-FST columns under explosive load. As compared with the modified HJC model, the modified K&C model has more accurate results. This phenomenon mainly accounts for the lack of ultimate strain of RPC (_EFMIN_). To analyze the reliability sensitivity of RPC-FST, an efficient probability analysis method is proposed based on the Kriging model and Monte Carlo simulation (MCS). The proposed method considers five nonlinear factors, including weight and distance of TNT, height and section diameter of RPC-FST, and steel tube thickness. Finally, the sensitivity of each factor is evaluated. Results show that TNT weight greatly influences the reliability of the RPC-FST, followed by TNT distance, RPC-FST height, RPC-FST section diameter, and steel tube thickness. In addition, the RPC-FST dynamic response analysis method based on the Kriging model and MCS can improve the calculation efficiency by more than 200 times compared with the ALE method. RPC-FST; dynamic response; modified K&C model; modified  
phase effect can be ignored [6; 7]. The LBE-based method and pressure-time history method have high computational efficiency. Nevertheless, these simplified methods lack a profound understanding of the functional mechanism between air and RPC-FST. Contrary to the aforementioned methods, the ALE-based method can accurately restore local details of blast conditions considering fluid-solid interaction (FSI) theory. Based on this method, [PERSON] [8] assessed the residual strength of fiber-reinforced concrete columns under explosion load. [PERSON] [9] investigated the blast resistance of a composite foam-core sacrificial cladding for steel-reinforced concrete structures. [PERSON] [10] investigated the dynamic response of ultra-high-performance cement-based composite-filled steel tube (UHPCC-FST) under close-range explosion. Besides the methods of applying explosion load, the material model is also a significant factor in precisely simulating the dynamic response of a structure under explosion load. The LS-DYNA program offers many dynamic constitutive models for simulating concrete materials, such as the Holmquist-Johnson-Cook (HJC) model and the Karagozian and Case (K&C) model. The HJC model is mainly suitable for material under large strain, high strain rate, and high pressure [11]. Based on the HJC material model, [PERSON] [12] established a theoretical model for shaped charge jets' penetration into concrete targets. [PERSON] [13] investigated the ballistic perforation resistance of concrete slabs. [PERSON] [14] calibrated parameters to investigate the blast resistance of ultra-high-performance concrete (UHPCs) slabs. It should be noted that the modified HJC model parameters are suitable for UHPCs slabs with 10.5% porosity of coarse aggregate. However, the applicability of HJC material model parameters modified for RPC materials with low porosity without coarse aggregate needs to be deeply investigated. Different from the HJC material model, the K&C material model has great advantages in describing the material under damage evolution, restraint effect, and shear expansion [15]. Based on the K&C material model, [PERSON] [16] estimated the residual axial load-bearing capacity of UHPCC-FST specimens subjected to contact explosion.