Design of pseudo strain-hardening cementitious composites for a ductile plastic hinge

The performance of the plastic hinge in reinforced concrete (R/C) frames using an Engineered Cementitious Composite (ECC) with tensile pseudo strain-hardening property is investigated. Under high shear stresses plastic hinge zones are known to perform in a brittle manner, which is mitigated in conventional design by heavy shear reinforcement. Prior to the use of the ECC in this application, various material design aspects were studied, and a comparative evaluation of ECC along with conventional fiber reinforced concrete (FRC) and plain concrete was carried out in tension, compression, fracture and shear. The selection of the particular material for this application is guided by the performance driven design approach. The structural performance requirement, namely ductility as measured by displacement ductility ratio and energy absorption capacity is related to the composite material properties such as tensile strain capacity, shear strain capacity and failure mode.; On the microstructure level, theoretical principles governing the effect of microstructural parameters on the uniaxial tensile properties were conceptually extended to material response under a general biaxial state of stress. Special focus is placed on uniaxial compression strength and shear strength of fiber reinforced composites. Subsequently the practical use of these micromechanical principles is demonstrated by designing an ECC with higher elastic modulus via fine aggregates, and validated by experiments on several plain paste and mortar matrix as well as fiber reinforced composite materials with and without pseudo strain-hardening behavior.; The biaxial compression-compression failure envelope for ECC is established as compared to that of plain concrete. Also, 'Ohno' shear beam tests were carried out on five different material systems, namely, plain concrete, reinforced concrete, ordinary fiber reinforced concrete, dramix fiber reinforced cement composite and spectra fiber reinforced ECC. The superior shear ductility coupled with the high tensile strain capacity and fracture toughness results in the choice of the ECC for the plastic hinge.; The performance of the plastic hinge using ECC is experimentally demonstrated under cyclic loading with high shear stress. A significant increase in displacement ductility and energy absorption capacity for the ECC plastic hinge is observed in comparison to the plain concrete hinge.