混凝土材料拉伸强度的应变率强化效应实验研究

Concrete-like materials have a clear strain-rate strengthening effect on tension strength. All specimens, including Brazilian discs and bars, were prepared and cured under the same laboratory conditions. The dynamic Brazilian split tests and the spalling tests were conducted by employing the Hopkinsion pressure bar as a loading platform. The failure processes of specimens in the tests were observed by using ultra-high speed camera and digital image correlation (DIC) method. In quasistatic or dynamic Brazilian split test, the disk specimen is assured to be splitted at the center of the disk. In spalling test, DIC analysis is applied to determine the exact timing and location of spall fracture, specifically in the case of multiple spallations. The dynamic tensile strengths of plain concrete discs and bars were obtained through these tests. The strain rate strengthening rules of split and spall tensile strengths are analyzed. The research results show that, for the dynamic split test, the central breaking only happens at relative low strain rate, and the critical strain rate is about 10 s^-1; the tensile strength and strain rates of multi-spalling can be achieved accurately by using a DIC-based analytical method; dynamic strain rate streng-thening rule of tensile strength are got by linearly fitting the experimental data, the increasing slope of tensile strength in spalling test is larger than that in dynamic Brazilian split test, and the dynamic increase factor of concrete can reach to above 5. The test results, based on the accurate measurements of tensile strength, can be used as a reference for the design and reconsideration of civil and military engineering.