Strain demand in boundary elements of concrete shear walls with hybrid steel-composite rebars

The present research investigates the strain demand of boundary elements of concrete shear walls reinforced with hybrid steel-composite rebars. In this regard, the numerical model of an existing full-scale sample has been done in VecTor-2.0 software and the results has been validated. Then, parametric studies were carried out for different values of the hybridization ratio where the cyclic response, maximum force, secant stiffness, single-cycle energy, displacement recovery index and strain values of the rebars are extracted. The results show that the combination of steel and composite rebars improves the hysteresis response of shear walls, maintains the post-yield strength, and increases the secant stiffness for lateral drifts over 1.9%. Also, this technique leads to a self-centering behavior minimizing the seismic damage. Hybridization with the combination ratio rh&ge0.2 provides strength and maintains the stability of the wall. Increasing the hybridization ratio higher than rh=0.3 only results in an increase in the strength with no residual displacement change. For walls with a low rebar hybridization ratio, the cyclic strain-displacement curves are asymmetric, but the behavior becomes symmetric and the maximum steel strain is reduced by 50% by increasing the ratio. The expansion in the steel strain cycles is insignificant for low hybridization ratios. However, it becomes more apparent with the increase of composite rebars. The effective straining height of the steel in the basic model is equal to half the length of the shear wall, but with the addition of composite rebars, this height increases up to 80% of the wall length, which indicates the yield distribution of the steel in a wider area of the member when it is hybridized with composite.