Stress Wave Propagation In Concrete Structure Under Impact Loading

Research on wave propagation in concrete structure under impact loading is not only the necessary precondition to estimate the load support capability of concrete structures, but also the important reference to design weapon performances, such as the way of penetration and the angle of penetration.One dimensional stress wave propagating in concrete structure is studied through a series of SHPB experiments. It is proved that the stress wave propagation velocity in the concrete states constant. The peak value attenuation of the stress wave is not quite obviously. The incident wave reflected from the free end of the concrete will influence the results. Several methods are proposed to remedy the disadvantage, such as shortening the length of the strike bar, making the strain gauges nearer to the strike end of the concrete bar, and lengthening the concrete bar.It is proved from the results of the triaxial compression experiments and tensile experiments of concrete that the compressive strength of concrete will become higher along with rise of the ambient pressure and parameters of concrete such as compressive strength, tensile strength, and elastic modulus are strain rate sensitive, which will be much more obviously when the order of magnitude of strain rates changed.Removing the pressure effect, the strain rate coefficient is determined from the test data of the uniaxial compression experiments for different strain rates. The normalized cohesive strength, the normalized pressure hardening coefficient, and the pressure hardening exponent are determined through the Mohr-Coulomb parameter and test data of the triaxial compression experiments.Numerical simulations are carried out to simulate the process of one dimensional stress wave propagation in the concrete. Parameters of JH model adopted in the simulations are determined in the dissertation. The reliability of the simulations is proved by comparing with the test data. Stress uniformity in the concrete is analyzed. Stress in sections ten centimeters far from the strike end is uniform. The result of the numerical simulations show that, strong stress wave will attenuate rapidly during propagation; once reaching the compressive strength of the concrete, the peak value of the stress wave will not attenuate any more; stress waves whose peak values are lower than the compressive strength will not attenuate in the propagation process.Through numerical simulations of explosion in concrete, stress wave propagations in concrete structures in both 2-dimensional condition and 3-dimensional condition are studied respectively. It is concluded that the peak value of the stress wave will attenuate sharply as the wave is propagating in the concrete structure, and the width of the pulse becomes wider and the rise time becomes longer with the wave propagating. Both material dissipation and geometric dispersion determine the attenuation law.