Structural evaluation of scaled double-layered containment structure against rigid missile impact

Abstract

In this experimental study, the scaled double-layer containment structure represented by 1000 mm × 1000 mm targets of outer reinforced and inner prestressed concrete of thickness 200 mm has been subjected to ballistic impact by 10 and 20 kg rigid missiles at incidence velocities, close to 100 m/s. The inner layer of prestressed concrete was cast with and without a monolithic rear steel liner of thickness 1.5 mm. The prestressing force was induced in the vertical and horizontal directions with respect to 15 % of the characteristic compressive strength of concrete (M45). In double-layer tests, the 20 kg missiles perforated the outer layer target with significant residual velocities, while the 10 kg missile just perforated the outer layer. The 20 kg missile, when impacted the inner layer prestressed concrete target with a rear steel liner, experienced no damage. However, when impacted, the prestressed concrete target without a rear steel liner suffered significant rear surface cracking but no scabbing of concrete. This concludes that steel liner plays a substantial role in mitigating rear surface cracking and minimizing damage to the inner layer target. The ballistic tests were also performed on single independent prestressed concrete targets with and without steel liner against 20 kg missiles. In single-layer tests, the target with the rear surface steel liner restricted the perforation phenomena, however, significant damage occurred to the concrete and the steel liner. On the other hand, the target without a steel liner underwent complete failure through perforation. Hence, steel liners not only controlled the rear surface cracking (in double-layer) but also effectively controlled the perforation phenomena (in single-layer). No loss of prestressing force was observed in the case of the double-layered configuration, however, when the missile impacted the single-layered prestressed concrete target, a noticeable loss of prestressing force was observed. The perforation limit velocities calculated using Modified NDRC, BRL-NDRC, CEA-EDF, UMIST, and Modified UMIST empirical models for reinforced and prestressed concrete targets were compared with the experimental results.