# Reliability Assessment of Steel-Lined and Prestressed FRC Slabs against Projectile Impact
## 1 Introduction  
A wide range of infrastructure facilities utilize prestressed concrete structural members, such as nuclear containment facilities, skyscrapers, buried and above-ground water tanks, tunnels, retaining walls, traffic barriers, and girder bridges. Steel lining is often used on some of these prestressed or non-prestressed structures, such as the outer containment of a nuclear power plant. Prestressed concrete structures are widely used because of their excellent shielding properties and safety against radioactive leaks and gas leaks. In addition, they are easy to maintain, strong, and ductile. An explosion, a projectile strike, an aircraft crash, or a vehicle collision may cause damage to these structures. Therefore, in addition to being safe under normal loading conditions, these structures must be safe during accidental overloading as well. The reliability of these structures under such complex dynamic loading conditions is often unknown in many of these cases. Recent studies have found that fibers are effective at improving the reliability of concrete against impact loading [1; 2; 3]. However, no study has yet investigated the reliability of prestressed fiber-added concrete (or prestressed fiber-reinforced concrete, PFRC) with steel lining against impact loading. Prestressed fiber-reinforced concrete (PFRC) has the benefits of both fibers and prestressing. The availability of fibers and prestressing increase concrete's tensile strength, resulting in higher flexural strength, shear capacity, and impact resistance for concrete members. Precast concrete (PC) and prestressed fiber-reinforced concrete (PFRC) have been studied much less than RC and FRC. In a study by [PERSON] et al. [4], nine slabs of reinforced concrete, post-tensioned concrete without reinforcement bars, and post-tensioned concrete with reinforcement bars were tested. They found that post-tensioned concrete with rebars had a greater impact resistance than concrete without rebars or reinforced concrete. Experimentally and numerically, [PERSON] et al. [5] examined the perforation resistance of plain concrete slabs that were impacted by steel projectiles of 20 mm diameter. They concluded that (i) the impact resistance of thin slabs is governed by tensile strength, and (ii) the ballistic limit of the slabs increases almost linearly with concrete strength. The punching strength of concrete slabs was studied by [PERSON] et al. [6] using a 47 kg hard projectile and longitudinal prestressing. Concrete had a compressive strength of 45 to 52 MPa. While permanent deflection was lower for prestressed concrete slabs without transverse reinforcement, the scabbed area was found to be more than RC elements. Residual exit velocity and scabbed area were significantly influenced by transverse reinforcement. [PERSON] et al. [7] validated their earlier published model for concrete slab perforation by rigid projectiles. Ballistic limits and residual velocities obtained by the model agreed well with several sets of concrete slab perforation data. [PERSON] et al. [8] studied the prestressed concrete (PC) slabs subjected to hard missile impacts. They found that prestressing and reinforcement ratio (due to prestressing bars) are the main factors affecting the ballistic resistance of PC slabs. They further observed that concrete confinement also increases the ballistic resistance of PC slabs. In situ prestressed concrete sleepers were studied by [PERSON] and [PERSON] [9]. Precast concrete sleepers were investigated for failure mechanisms, impact energy absorption, flexural toughness, crack propagation, and energy transfer mechanisms. In the study, it was found that split cracks are the prime cause of prestressed concrete sleeper failure. In a study, [PERSON] and [PERSON] [10] examined the ballistic performance of 45 cm \(\times\) 45 cm slabs of plain concrete, reinforced concrete, and prestressed concrete using steel projectiles of 1 kg weight. The slabs ranged in thickness from 60 mm to 100 mm.