Local response of reinforced concrete to missile impacts

An experimental and computational study was undertaken to determine the response of reinforced concrete walls to impacts from postulated tornado and other missiles. The study included laboratory-scale missile impacts, experiments to characterize concrete, computational model development, and two-dimensional simulations of missile impacts. Impact experiments with rods and pipes on small reinforced concrete walls showed crushing, cratering, spalling, radial cracking, and plug formation. The mechanisms governing this material response appear to be crushing, shearing, and tensile fracture. Static triaxial and dynamic plate impact experiments were used to determine the material properties. Dynamic strengths were higher than static; tensile strengths were ten times as high. A CAP constitutive model developed for concrete described compaction, Mohr-Coulomb yielding, and tensile separation following tensile strain accumulation. Model parameters were derived separately from the dynamic and the static data. Two-dimensional computational simulations were made of a rod impact experiment with threshold cracking using both static and dynamic parameters. The correct locations of fractures were predicted with the static parameters, but penetration and severity of failure were overpredicted. Penetration distance was correctly given with the dynamic parameters, but fracture was underpredicted. A model combining dynamic shaer and compaction properties with intermediate-rate tensile properties may be appropriate.