Finite-element modeling of actively confined normal-strength and high-strength concrete under uniaxial, biaxial, and triaxial compression

A concrete strength-sensitive finite element (FE) model applicable to concrete subjected to various confining pressure levels and conditions is presented. This paper focuses primarily on the failure surface and flow rule of concrete in multiaxial compression, which were experimentally observed to vary with the unconfined concrete strength and level of confining pressure. To this end, a large experimental database, which consists of more than 1,700 results of concrete specimens tested under biaxial and triaxial compression, was assembled through an extensive review of the literature. This database was augmented with another test database of concrete in uniaxial compression that consists of more than 4,000 test results. Based on the test database results, it was observed that the tangential slope of the failure surface reduces with an increase in the unconfined concrete strength and confining pressure. The concrete dilation angle considered in the flow rule was observed to be nonlinear throughout loading history. To incorporate the observed changes in the failure surface and flow rule of concrete subjected to uniaxial, biaxial and triaxial compression, an extension of Lubliner's concrete-damage plasticity model was proposed and presented in this paper. Comparisons with experimental test results show that the predictions of the extended model are in good agreement with the test results of both normal-strength concrete (NSC) and high-strength concrete (HSC).