Equivalent damping ratio model of flexure-shear critical RC columns

•Hysteretic loop expression of flexural-shear critical RC columns under complete cyclic loading is developed.•An equivalent damping ratio model suitable for flexural-shear critical RC columns is proposed.•A design example of two-column pier supported bridge is provided to illustrate the application of the proposed model. To describe the hysteretic behavior of flexure-shear critical reinforced concrete (RC) columns realistically, a hysteretic loop expression of flexure-shear critical RC columns under complete cyclic loading is proposed by investigating the characteristics of column specimens in PEER - Column Database. For the proposed expression, important characteristics of flexure-shear critical RC columns under cyclic loading, including pinching and stiffness degradation, are covered. And then, an equivalent damping ratio model suitable for flexure-shear critical RC columns is proposed by using the proposed hysteretic loop expression based on the Jacobsen’s approach. The relationship between the equivalent damping ratio formula of two-column pier supported bridge and that of its columns is developed based on the energy dissipation capacity. A design example is provided to illustrate the application of the proposed model.