Resistance of a concrete target to penetration of a rigid projectile - revisited

• Published in: International journal of impact engineering Vol. 106; pp. 30 - 43
• Main Author: Yankelevsky, David Z.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2017; Elsevier BV
• Subjects: Advanced material testing; Compressive strength; Computation; Concrete; Concrete penetration models; Empirical analysis; Equation of state; Failure analysis; Material properties; Materials science; Mathematical models; Penetration depth; Penetration resistance; Thermodynamics; Advanced material testing; Concrete penetration models; Equation of state; Material properties
• ISSN: 0734-743X; 1879-3509
• DOI: 10.1016/j.ijimpeng.2017.02.021

•Concrete resistance to penetration is a major parameter, the proper modeling of which is essential for reliable modeling of the problem.•Review of different models shows that the concrete unconfined strength is a common identifier of its resistance to penetration.•Penetration tests with different mix designs and same unconfined strength exhibit entirely different resistance and damage characteristics.•The entirely different behavior of different mixes with same unconfined strength is demonstrated experimentally at the material specimen level.•The unconfined strength is found to be an inappropriate identifier of concrete resistance.•A mix design based constitutive relations are required to properly characterize concrete resistance to penetration.•A broad experimental program aiming at such formulation is ongoing. Penetration into concrete is a subject of much interest and importance that attracts researchers for many years. This paper aims at reviewing the major contributions to model the deep penetration of a rigid projectile that perpendicularly hits a concrete target with emphasis on concrete target resistance. With regard to the concrete target resistance there exist four major modeling families: empirical, semi-empirical, analytical and theoretically based computational models. The paper overviews representative models and shows what target resistance parameters are used in these models and discusses some inherent weaknesses. The paper mainly refers to the dependence of concrete target resistance on the material characteristics; the concrete unconfined strength clearly appears to be the major identifier of the target resistance in these models. In many expressions the penetration depth is inversely proportional to the square root of the unconfined strength. The paper debates with this formulation which correlates the target resistance with the unconfined compression strength through a smooth continuous function of the strength disregarding the effect of different concrete mix designs that produce the same unconfined strength. Our own experimental studies are described to prove that concrete targets of similar unconfined strength demonstrate different resistance and damage depending on the different concrete compositions. Attention is given to the comprehensive description of target resistance via the equation of state and the failure envelope; this material behavior presentation is common in computational models, and is also adopted, although in a very simplified form, in analytical models. However, it will be shown that these advanced models are also commonly identified through the unconfined strength, and therefore they poorly describe the specific characteristics of the material under discussion. There is a need to produce refined data for the equation of state and of the failure envelope that are related to the concrete mix characteristics. Recently a new wide scope testing program has been initiated at our laboratory to achieve that goal, and early results have already been produced.