Channeling effects due to explosions in urban environments

DANIEL AMBROSINI; RAMÓN CODINA; FERNANDA DE BORBÓN

Simposio; 15th ISIEMS International Symposium on the Interaction of the Effects of Munitions with Structures,; 2013

In the last years, terrorist attacks around the world proved that it?s important study the effects of bursts on urban environment. The facades of buildings in urban explosions can obstruct the passage of shock waves. This generates reflected waves that impact on targets in the street again. These reflected waves combine with the incident waves generating even more destructive wave fronts. This is usually referred to as ?street channeling? or the ?canyon effect?. The estimation of actions for the design of blast resistant structures has traditionally been performed, using over-pressures and impulses derived from empirical methods or analytical simplified methods, from technical manuals like UFC 3-340 or software like CONWEP. This kind of procedures, are suitable for perfectly spherical or semi-spherical bursts (above of ground level), but not for other problems with more complex charge geometries or situa-tions where there are multiple wave reflections. At present, there are numerical tools (hydrocodes) that combined with parallel processing computation allow to ob-tain more realistic results. In this paper a parametric study of explosions in urban environments is carried out. The objective of this study is to determine the confinement effects upon the explosions in urban environments. First, it was determined the most representative street widths in typical cities. The study took into account two posi-tions for the explosive, centered with the axis of the street, and located 2.20 meters from one of the facades. The latter coincides with the limit of a typical sidewalk. Finally, different masses of explosives were considered. In order to quantify the effect of confinement, records of overpressures and impulses at gauge points of the mesh were compared, for both confined and unconfined explosions. Thereby, confinement coefficients of overpressures and impulses were obtained for different street widths and different amounts of explosive. The study carried out allows define different zones of confinement within a street, and how they are affected by changing some parameters such as the street width or the explosive amount.