Reliability of RC shielded steel plates against the impact of sharp nose projectiles

• Experimentally studied response of RC shielded steel plates against impact loads.
• Ogive and bi-conical nose shape projectiles were used for impacting the target.
• Presented a probabilistic procedure for reliability study of RC shielded steel plate.
• Proposed a formula for converting bi-conical nose into equivalent conical nose.
• Validated the projectile nose equivalence through experiments.

Reinforced Concrete (RC) shielded steel plates are extensively employed in double wall containment structures. In such structures, RC shield surrounds the inner steel shell/plate, and inner steel shell/plate acts as a barrier against the release of radiations. Although a substantial research is available on impact studies of concrete, reinforced concrete and steel plates, the studies on RC-shielded steel plates are not widely available. Also how the uncertainties involved in the design parameters influence the reliability or safety of RC shielded steel plates is not very well known. In the present study, a simple experiment was designed to simulate a double-wall containment (i) to study the response of RC shielded steel plates against the impact of single (ogive) and double nose (bi-conical) shaped projectiles, and (ii) quantitatively evaluate how much safe the inner wall (steel plate) is under the impact of these projectiles. To achieve the above objectives, the study was carried out in two parts. In the first part, experiments were conducted by studying the impact resistance of RC shielded steel plates of 600 × 600 × 5 mm thickness against the impact of non-deforming projectiles of ogive and bi-conical nose shapes. The steel plate was placed at a clear distance of 75 mm from 60 mm thick RC slab. The specimens were tested at varying projectile impact velocities. Investigations were carried out to measure damage level in steel plate in terms of its deformation, fracture and perforation. In the second part, reliability analysis of all the tested concrete shielded steel plates was carried out using Monte Carlo Simulation technique for a range of impact velocities. The results of the reliability analysis were then used to relate the probability of failure with different scenarios of the failure of the specimens. The effect of RC shield thickness and steel plate thickness on the reliability of RC shielded steel plate against the impact of bi-conical and ogive nose projectiles were also studied on parametric basis. In order to use the available formulation on conical nose shape projectiles, the bi-conical nose was replaced by an equivalent conical nose for which a simple formula was derived. In order to validate this simplified attempt to suggest an equivalent conical nose, one of the tests with bi-conical nose projectile was repeated with the equivalent conical nose projectile. At a given striking velocity, the equivalent conical nose projectile produces a similar damage pattern and the same damage level in the RC shielded steel plate, as that of bi-conical nose projectile at the same impact velocity.