Previous post-earthquake studies on reinforced concrete (RC) structures have reported severe structural damages in the plastic hinge regions of lower-story RC columns, and suggested that columns with short shear-span ratios may fail in shear after flexural yielding due to shear deterioration in their plastic hinge regions before reaching the ultimate ductility demand.
To ensure the ductile collapse mechanism of an RC frame, it is not only important to know the shear strength of the RC columns but also their deformation capacity. The current seismic design provisions of ACI 318-14 disregard the concrete shear contribution for RC columns subjected to a medium level of axial force to indirectly account for ductility.
This study experimentally investigates the deformability of RC columns failing in shear after flexural reinforcement yielding and proposes an analytical model to estimate the rotation capacity of such columns. The proposed model provides a direct evaluation method for estimating the deformability of RC columns by considering the potential shear degradation after flexural yielding.
This approach employs the equilibrium and compatibility formulation of existing compatibility-aided truss models. Comparing the analytical results with an extensive test database indicated that the proposed model can predict the deformation capacities of RC columns failing in shear after flexural yielding with reasonable accuracy.