ON A VERY HIGH RATE SENSITIVITY OF CONCRETE FAILURE AT HIGH LOADING RATES AND IMPACT

Abstract

During last decades, there has been increasing interest in the effect of high strain rates on mechanical behavior of materials including fracturing of rocks and rock-like materials such as different concretes. The subject of this contribution is on recent results of concrete testing at high strain rates in tension, compression and shear. The so-called pseudo-viscosity of compression failure discovered recently at high strain rates is analyzed. Special attention will be given to the recent results obtained in France, and in particular at Metz University, for dry and wet concrete loaded at different rates in tension. Experimental technique applying wave mechanics will be discussed anew to test brittle materials at high strain rates in tension. This technique is based on the phenomenon of spelling combined with the Hopkinson measuring bar. The results obtained in LPMM-Metz for the tension mode of failure will be compared with the recent results obtained in tension and shear modes at the University of Florida. It has been found that a high “anisotropy” of failure occurs for different modes of failure at high strain rates. The highest rate sensitivity is found in tension and the smallest in compression. The rate sensitivity in the shear mode is closer to the tension case. Clearly, the hydrostatic component of stress affects strongly the failure mechanisms of brittle materials. Finally, a model of failure applicable to short-time loading, which is based on the statistics of Weibul, will be mentioned.