STUDY OF HIGH RATE OF DEFORMATION OF PRESTRESSED CONCRETE SLABS

Abstract

This study is based on the ballistic evaluation of plain, reinforced, and prestressed concrete slabs investigated by performing experiments and finite element computations. A new material model for reproducing the behavior of concrete has been developed by introducing some modifications in the original Holmquist Johnson Cook (HJC) model. The ballistic experiments were performed on 100, 80 and 60 mm thick plain, reinforced, and prestressed concrete slabs against steel projectiles at the incidence velocities close to ballistic limit. The reinforced concrete slabs of each thickness were cast with two different reinforcement configurations. The first configuration reinforced concrete slabs had identical reinforcement in both orthogonal directions with respect to 8 mm diameter @ 90 mm c/c with a nominal cover of 10 mm. While in the second configuration reinforced concrete slabs, the 8 mm diameter bars were provided @ 90 mm c/c with a nominal cover of 10 mm in both orthogonal directions. In addition, the high strength steel prestressing wires of 7 mm diameter were provided @ 40 mm c/c, but no prestressing was induced. The reinforcement in the prestressed concrete slabs was provided identical to the reinforcement provided in the first reinforced concrete slabs (8 mm diameter @ 90 mm c/c in both orthogonal directions with a 10 mm clear cover) along with the high tensile strength steel indented prestressing wires of 7 mm diameter @ 40 mm c/c at the centre of the slab thickness in one direction to induce the uni-directional prestressing force. The prestressed concrete slabs of 60 and 80 mm thickness were cast with two different levels of prestress (LOP) as 12% and 24% while the 100 mm thick prestressed concrete slab was cast with single level of prestress as 8%. The damage in the concrete slabs was described in terms of cracking and cratering. Cratering was measured in terms of size and volume of crater at the front and rear surface of concrete slabs. Also, the residual velocity of the projectile and ballistic limit of the concrete slabs were obtained.