| This research is to study behavior of concrete under dynamic compressive loading. Unconfined high-strength concrete specimens were uniaxially tested on a three-inch-diameter Split Hopkinson Pressure Bar. From the experimental data, a rate-dependent model for the uniaxial unconfined compression case was proposed, which included inelastic-strain-rate dependence of stress up to failure and a failure-initiation criterion of an accumulative type. Furthermore, an overstress-type elastoviscoplastic constitutive model for the three-dimensional stress case was constructed to combine a proposed static elastoplastic cap model for concrete with the characteristics of concrete under dynamic loading, which were observed by the dynamic tests of this research.; The proposed elastoviscoplastic model was then implemented in a two-dimensional time-varying finite element program, which is applicable to concrete and concrete structures under impulsive loading. As a computation example, the program was applied to the geometry of the concrete specimen so that computation results were compared with experimental data to validate the accuracy of the constitutive model.; In addition to the extensive experimental investigation of high-strength concretes and the modeling and computational studies, a preliminary experimental investigation was made of the crack accumulation in smaller specimens of a concrete of moderate strength after various amounts of deformation. This was accomplished by interrupting the tests after various amounts of deformation, so that micrographic examinations could be performed on sections cut from the intact recovered specimens. |
