Response of reinforced concrete structural elements to near-field and contact explosions

The integrity of buildings and the safety of their occupants can be catastrophically affected by the action of contact or near-field explosions. Numerical simulation studies should be carried out in order to better understand the response of reinforced concrete (RC) structures to such dynamic impulsive actions. When concrete structural elements are subjected to near-field blast loads, large deformations, rate effects and overloading render the modelling of concrete extremely complex. Significant research has been done since September 11, 2001, in order to improve the computational abilities, to understand the complex non-linear behaviour of concrete under extreme loading conditions and to obtain reliable numerical results. Simulations can be done using 'user-developed' codes or commercial hydrocodes. One of the most common hydrocode is LS-DYNA, where concrete can be treated as a homogeneous material. In this particular project LS-DYNA is used along with the Winfrith Concrete Model to simulate the response of a two-layer RC slab to several contact detonations (using C4, Composition-4). The aim is to achieve a contact explosion between the target (slab) and the explosive since literature can provide us with only limited information regarding this. The slab and the high explosive are explicitly modelled using the multi-material arbitrary Lagrangian-Eulerian approach (MM-ALE). The obtained numerical results are validated using experimental data. The aforementioned numerical results of the damage are in favourable agreement with the experimental data, with average errors lying under 10%. In addition, it was observed that the increase in the explosive mass led to a change of the damage mode from penetration to perforation. Concrete's crack pattern was also investigated.