Application of 2D to 3D ALE mapping in designing a large-scale column under a close-in detonation

The Arbitrary Lagrangian-Eulerian (ALE) formulation is an effective approach to model structural performance under blast load with consideration of fluid-structure interaction. However, this method is highly sensitive to air domain and structural mesh sizes, leading to an increased computation time and resource for an accurate prediction of blast wave magnitude, propagation, and interaction with structure. Therefore, this paper aims to utilise the application of a 2D to 3D ALE mapping technique to design a large-scale reinforced concrete (RC) column against a close-in vehicle-borne improvised explosive device (VBIED). The analysis of the column response was conducted through a three-stage process: preloading under vertical loads, blast effect assessment on the preloaded column, and evaluation of the residual load-bearing capacity of the blast-damaged column. A 2D Arbitrary Lagrangian-Eulerian (ALE) model was initially developed and validated against the Kingery-Bulmash empirical model. From this validated model, a VBIED blast event was detonated to generate blast pressure waves within the free air domain. The 2D simulation was terminated before the blast wave fully traversed the standoff distance to the structural surface. The blast pressure waves were then mapped onto a 3D ALE model incorporating the preloaded column, where key parameters including fluid-structure interaction (FSI), strain rate-dependent material properties, equations of state (EOS), and boundary conditions were rigorously defined to ensure an accurate representation of blast-structure interaction. The blast performance of the column from the 2D to 3D mapping model, including column damage and displacement time histories, was also compared with the conventional 3D ALE model. Finally, the residual axial capacity of the damaged columns was determined by using an incremental displacement-controlled load. The structural responses of the columns demonstrated comparable behaviour in both the conventional 3D ALE model and the 2D to 3D mapping ALE approach. However, the 2D to 3D mapping method achieved a substantial reduction in computational time while utilising the same computational resources. Additionally, recommendations for efficient and accurate use of the 2D to 3D ALE mapping method for designing RC structures were presented in this paper. The findings of this study provide valuable insights for engineers and researchers in structural blast engineering, facilitating the efficient application of 2D to 3D ALE mapping techniques in the design and analysis of RC structures subjected to blast loads.