Experimental evaluation of scaled post-tensioned concrete walls under rigid projectile impact

The inner containment wall (ICW) of a double-layered nuclear containment structure is a prestressed concrete (post-tensioned) wall designed to be crack-free and prevent radiation leakage. It also includes an inner metallic steel liner for enhanced leakage protection. The present study investigated the ballistic resistance of scaled post-tensioned concrete walls, with and without a steel liner, against 10 and 20-kg rigid missile impacts. The ballistic tests were performed at incidence velocities close to 100 m/s, approximating aircraft landing speeds. The post-tensioned walls, with dimensions of 1000 mm × 1000 mm and a scaled thickness of 200 mm, were prepared both with and without a rear steel liner (1.5 mm). The pre-stressing force was applied in orthogonal directions using a hydraulic jack at 15 % of the characteristic strength of M45-grade concrete. Post-tensioning was achieved using a robust anchoring assembly system that includes high-strength steel strand wires , anchoring cones and heads, anchoring wedges, and galvanized carbon steel sheathing ducts. The experimental investigation concludes that tendons prevent perforation when directly impacted by a projectile, although significant damage occurred to the anchoring assembly. In addition, the rear steel liner also plays a significant role in restricting the perforation phenomena, although it incurred significant bulging deformation. The unbonded tendon wires rebounded the missile (20 kg) approximately 9 m away from the target due to the bow-and-arrow effect. As a result, the unbonded wall experienced less damage compared to the bonded walls. Under low-energy impact (10 kg projectile), the post-tensioned wall with a steel liner experienced front penetration of 55 mm, with no visible damage to the rear steel liner. However, significant cracking occurred across the entire inner concrete rear surface. The strain time histories of the steel liner and strand wires were recorded during the impact phenomena. The concrete penetrability factor ( K ) is modified to incorporate the effect of the prestressing force in the NDRC expression. • Scaled post-tensioned concrete walls were subjected to rigid projectile impacts. • Ballistic performance of the rear steel liner has been investigated. • The effects of bonded and unbonded tendons on the ballistic performance of post-tensioned walls has been investigated. • Failure modes of post-tensioned walls with two different tendon arrangements were investigated. • The performance of the anchoring assembly system was evaluated.