Plasticity Model for Hybrid Fiber-Reinforced Concrete under True Triaxial Compression.

Based on the experimental background of 75 true triaxial compression tests conducted on cubic specimens, a plasticity constitutive model for hybrid steel-polypropylene fiber-RC (HFRC) is developed in this study, aiming to accurately predict the strength and deformation of HFRC under various loading scenarios. A five-parameter Willam-Warnke failure surface is modified to account for the presence of hybrid fibers. The evolution of the loading surface is characterized by uncoupled hardening and softening regimes determined by the accumulated equivalent plastic strain, and a Drucker-Prager nonassociated plastic flow is used to describe the plastic deformation. Various model parameters are mainly calibrated on the basis of true triaxial compression test data. Subsequently, the responses of the constitutive model are verified by multiaxial compression test results of both plain concrete and fiber-RC reported by various researchers. It is observed that a good estimation of the strength and the deformation capacity of HFRC with varying fiber volume fractions and aspect ratios can be achieved by the proposed model. [ABSTRACT FROM AUTHOR]