Plastic hinge behavior and rotation capacity in reinforced ductile concrete flexural members

Ductile concrete materials, such as high-performance fiber-reinforced cementitious composites (HPFRCCs), are being considered as a new material that can be used in plastic hinge regions of buildings and bridges to reduce damage as compared to ordinary reinforced concrete. In flexure, a highly nonlinear plastic strain distribution of the primary tensile reinforcement is observed at dominant crack locations, leading to significant differences in plastic hinge length and behavior as compared to ordinary reinforced concrete flexural members. In this study, two-dimensional finite element models were validated with experimental results using a recently developed bond-slip constitutive model, which aids in simulating multiple damage states, such as yield and collapse level drift states. After validation, the modeling approach was used to study the plastic hinge region behavior of reinforced HPFRCC flexural members with variations in mechanical properties, boundary conditions, and geometric properties. The particular areas of interest were reinforcement yielding location, plastic strain distribution, and curvature localization region. New expressions were proposed to predict the equivalent plastic hinge length, L_p, using variables such as shear-span, tensile strength of HPFRCC, reinforcement ratio, yield strength of the reinforcement, boundary condition, and loading scenario. Proposed equations for plastic hinge length of reinforced HPFRCCs are incorporated into a mechanics-based approach to predict rotational capacity of flexural members. The analytical approach was also shown to estimate yield and nominal flexural strength with reasonable accuracy. The proposed methodology is compared with experimental results and expressions for plastic hinge length found throughout the literature for reinforced concrete and HPFRCC members. The results of the study will help practicing engineers and researchers simulate the performance of reinforced HPFRCC flexural members in a computationally efficient manner.