Numerical simulation of damage of low-rise RC frame structures with infilled masonry walls to explosive loads

Terrorist bombing attacks on civilian structures could cause catastrophic effect with loss of lives and properties. Recent published US DoD (United States Department of Defence) anti-terrorist and US DoD Explosive Safety Guidelines give safe stand-off distance for building structure protection. However, the definition of structural damage and structural types and configurations in those guidelines is vague. To have a clearer picture of structural damage, it is therefore very important to carry out further studies to define damage severity of various structures under different explosion scenarios. As blasting tests are not only very expensive, but also in many cases not possible owing to safety consideration, predictions of structural damage with reliable numerical means become very important. In this study, numerical analysis of structural response and damage to surface explosions is carried out. A one-storey and a two-storey masonry infilled RC (reinforced concrete) frame are used as examples. Nonlinear orthotropic material model is employed to model RC frames and a homogenized masonry material model is used for masonry infilled walls. Strain-rate effect on RC material properties is included in the model. The commercial software LSDYNA3D (Whirley and Englemann 1991) with user defined material model subroutines is used to perform the numerical calculations. Structural damage levels corresponding to the various stand-off distances are defined from the numerical results. The results are also compared with the stand-off distances recommended in the US DoD Anti-Terrorist and Explosive Safety Guidelines.