Constitutive Law of Concrete Under Multiaxial Compression Considering Strain Localization in Strain Softening Region

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In this study, the constitutive relationships of concrete under multiaxial compression including strain softening region were examined both experimentally and analytically. The results obtained are summarized as follows.1. It is reasonable to treat the constitutive law of confined concretes as that of plain concrete under multiaxial stress state, judging from the view point of failure mechanism. However, the experimental data concerning strain softening of the concrete under multiaxial compressive stress state are still inadequate to establish the general law.2. The stress-strain relationships of concrete specimens of various shapes are successfully associated with each other, using the proposed idealized failure zone model, regardless of the magnitude of lateral stress and compressive Strength of concrete.3. The plastic deformation capacity of high-strength concrete under multiaxial compressive stress state can be treated as the extension of that of normal strength concrete. In this study, the earlier proposed model for representing the stress-strain behavior in the maximum compressive stress axis was extended for the high-strength concrete.4. It is possible to represent the effects of various factors (such as magnitude of lateral stress, imbalance of two lateral stresses, pitch of loading area of lateral stress, loading path of lateral stress, and shape of concrete specimen) in the form of the reducing coefficient of the lateral stress. In this study, the coefficients were numerically represented, based on the experimental data.5. It is not appropriate to use the loading surface defined in the stress space for modeling the strain softening of concrete. Therefore, a new type of constitutive model was proposed in this study, based on the plasticity theory defined in the strain space.6. It is demonstrated that the proposed constitutive model is quite useful to predict the strain softening behavior of concrete under triaxial compression state.