Seismic Shear Strength Capacity Modeling for Corroded-Stirrup RC Bridge Pier Columns That Failed in Flexure-Shear Mode

To study the seismic performance and shear strength capacity of flexure-shear critical RC bridge pier columns, including the corrosion effects of stirrups, low-cycle cyclic loading tests were conducted on nine circular pier columns with different corrosion levels of reinforcing bars (including the longitudinal bars and stirrups). The results showed that stirrup corrosion is more server than longitudinal bar corrosion in the pier columns under the same corrosion conditions due to the different protective effects of concrete protective layers with different thicknesses. The shear strength and deformation capacities of the pier columns are significantly reduced due to mechanical property degradation of corroded reinforcements as corrosion increases, and the columns are prone to evolve from ductile flexure failure to low-ductile flexure-shear failure. Compared with the uncorroded control column specimens, the peak lateral load and displacement ductility of the corroded specimens decreased by 16.79% and 34.78%, respectively, at approximately 20% theoretical stirrup corrosion ratio. In addition, the shear strength of flexure-shear critical corroded columns was defined to be distinct from that of shear critical corroded columns, and a novel model for estimating the shear strength capacity of flexure-shear critical columns with corroded stirrups was proposed.