The analysis of explosives in contact or very near to reinforced concrete (RC) structures is an important aspect in the design of protective structures and vulnerability assessments. Although this remains a topic of high importance for defence, a more widespread interest has developed as civilian structures become the targets of terrorism. This type of assessment requires a robust simulation method for coupled fluid-structural interactions (FSI) which can handle the explosive detonation, air blast propagation, structural deformation, and damage evolution. This paper describes the application of a loose-coupling method which combines the FEFLO CFD code and SAIC's CSD code for 3D numerical simulations of unconfined and semi-confined explosions near RC structures. This approach takes advantage of the unstructured tetrahedral mesh for the CFD and an embedded method for CSD structures inside the fluid domain. Comparisons of simulations with experiment provide validation, but also reveal some weaknesses of the method. A good agreement between simulation and experiment is found with moderate explosive loading. However, a severe explosive loading with confinement results in extensive damage to the structure which is difficult to reproduce in simulations.