SEISMIC BEHAVIORS OF HYBRID FRP-STEEL REINFORCED ECC-CONCRETE COMPOSITE COLUMNS

It proposes a novel approach to improve the seismic behavior of hybrid FRP-steel reinforced concrete columns through the employment of high ductile engineered cementitious composites (ECC) in the plastic hinge region. A number of hybrid FRP-steel reinforced ECC-concrete columns were tested under reversed cyclic loading. The influence of matrix type, reinforcement type and axial force ratio on the seismic behaviors of columns in terms of failure mode, crack pattern, load carrying capacity, residual deformation, ductility and energy dissipation capacity were systematically investigated. It is found that the substitution of concrete with ECC in plastic hinge region can efficiently avoid the local buckling of FRP bars and thus significantly improve the seismic performance of the columns. Compared with the steel reinforced ECC-concrete composite column, the hybrid reinforced composite column exhibits evidently lower residual deformation and obviously higher post-yielding stiffness. With the increase of axial force ratio, the ultimate strength increases while the deformation capacity decreases. Through finite element parametric analysis, it is found that the ultimate strength and deformation capacity of the composite columns increase with the increase of the ECC compressive strength as well as the total reinforcement ratio; with the total reinforcement ratio remaining unchanged, the higher the area of FRP reinforcement, the better the ductility of the column.