## 5 Conclusions  
The displacement prediction model of RPC-FST under random explosion load is established based on fluid-solid interaction (FSI) theory. The main conclusions are as follows:  
(1) The modified K&C model has higher accuracy than the modified HJC model in calculating the dynamic response of RPC-FST columns under explosion load. This is mainly because the previous HJC model is applicable to RPC materials with coarse aggregate and porosity of 10.5%. Although the HJC model is calibrated by modifying the porosity and related parameters, a lack of test for the ultimate strain of RPC (_EFMIN_) caused the calculated deflection to be lower than the test deflection in the modified HJC model. (2) It takes a long time to use the ALE method to carry out the numerical calculations under RPC-FST explosion loading. The updated Kriging surrogate model can significantly \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Testing Sample**} & \multicolumn{3}{c}{**Total CPU Time (s)**} \\ \cline{2-4}  & **Modified HJC Model** & **Modified K\&C Model** &
\begin{tabular}{c} **Kriging** \\ **Surrogate Model** \\ \end{tabular} \\ \hline
1 & 9562 & 15,423 & 67 \\
2 & 15,447 & 19,661 & 70 \\
3 & 11,212 & 15,223 & 62 \\
4 & 11,329 & 18,195 & 69 \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Efficiency competitions of three models. Figure 8: (**a**) Sensitivity factor of each parameter and (**b**) local reliability sensitivity of each parameter. shorten the required time for the FSI theoretical analysis by more than 200 times. Besides, the RPC-FST dynamic response analysis based on the updated Kriging surrogate model has high accuracy. (3) Based on the analysis of the five random parameters by the Kriging surrogate model, the TNT weight has the most significant impact on the risk of maximum displacement of RPC-FST compared with other parameters. Z.J. : investigation, software, formal analysis, original draft, writing--review and editing. Q.R. : investigation, methodology, software, formal analysis, funding acquisition, writing--review and editing. X.H. : methodology, formal analysis, writing--review and editing, funding acquisition. Z.Z. : investigation, software, writing--review and editing. E.Y. : writing--review and editing. All authors have read and agreed to the published version of the manuscript. This research was funded by the Excellent Youth Foundation of Heilongjiang Province: No. YQ2019E028; National Natural Science Foundation of China: No. 52078169; Outstanding Young Talents Project of Harbin University of Science and Technology: LGYC2018 JQ018. This contribution is supported by the National Natural Science Foundation of China (No. 52078169), Excellent Youth Foundation of Heilongjiang Province (No. YQ2019E028), and Outstanding Young Talents Project of Harbin University of Science and Technology (LGYC2018 JQ018). The authors declare no conflict of interest. The HJC model is a constitutive model proposed by [PERSON] [46], which solves the problem of large deformation of concrete under high strain rate. At present, the HJC material model is widely used in the dynamic impact failure process of UHPCs [14; 16; 47]. Therefore, the applicability of the HJC model for RPC needs to be further discussed. The HJC constitutive model mainly includes three parts: the equation of yield surface, equation of damage evolution, and equation of state. The damage evolution equation and state equation of the HJC model will be modified. The parameters of yield surface equation are modified by [PERSON] [14]. The modification of yield surface equation will not be explained here. The modified HJC model process is shown in Figure A1. The damage evolution equation considers the damage of equivalent plastic strain and plastic volume strain.