Examples of dynamic test procedures for steel fibre reinforced concrete

Abstract

The aim of this work is to present some examples of experimental tests, which can be usefull for characterizing the resistance to failure of special steel fibre reinforced concrete – SFRC, intended especially for security use in the framework of ballistic and explosion protection. The first type of the tests was the strain gauge - based characterization of the dynamic response of the SFRC concrete block under ballistic loading. The tests were aimed at measuring the deformation response of a concrete specimen of 500 x 500 x 105 mm in dimensions upon the impact of a projectile. The tests were used to support the development and verification of numerical simulation models. For numerical simulations 3D models of individual projectiles were developed. Four T-type strain gauges were glued according to the geometric scheme on the opposite side of a specimen, i.e. on the side behind the impact of the projectile, and they measured the deflection of the plate after the impact of the projectile. The strain response records obtained from the strain gauges were subsequently used for numerical analyses by the use of the LS-DYNA software. The average maximum deflection of the plate at the impact of the projectile was characterized by the strain 400 µm/m. The second type of the tests was concerned with the method of measuring the quasi-dynamic tensile strength of special concrete specimens using an instrumented Charpy tester. The results compare both the breaking energy and the maximum force achieved for hobby concrete (HB) and hobby concrete with wires (HBD) specimens. These were pilot tests to develop the most suitable testing method. For the HB and HBD specimens the maximum force in the tests was found to be 55 N vs. 600 N, and the breaking energy to be 0.4 J vs. 1.3 J.