A modelling approach for existing shear-critical RC bridge piers with hollow rectangular cross section under lateral loads

Most of the existing Reinforced Concrete (RC) bridges were designed before the recent advancements in earthquake engineering and seismic codes. The performance assessment of these bridges is, therefore, a crucial issue for seismic safety of bridge infrastructures and estimation of losses due to seismic events. Despite the seismic assessment of columns with solid cross-section in ordinary buildings may be considered as quite comprehensive, a similar conclusion cannot be drawn for shear-critical hollow core piers, widespread in existing bridge structures. The present work aims at contributing to the investigation about the response of RC piers with hollow rectangular cross-section under cyclic loading. The main goal of the study is the definition of a comprehensive and practice-oriented modelling approach for the assessment of seismic response of RC hollow rectangular piers, able to account for all the deformability contributions, and, particularly, able to reliably predict drift-capacity at shear failure and subsequent degrading stiffness. A three-component model, accounting for flexural flexibility, shear flexibility and slippage of rebars is adopted. The shear capacity assessment is dealt with more in details. A proper experimental database is collected, made up of cyclic tests on hollow rectangular piers failing in shear, with or without yielding of longitudinal reinforcing bars. A new empirical formulation for the assessment of the displacement capacity at shear failure, specifically for the investigated structural elements, is calibrated. The degrading stiffness also is empirically calibrated to completely define the degrading shear response. Finally, the proposed numerical model is validated through the comparison with the experimental results carried out by the Authors (also in terms of local deformability contributions) and with test results collected from literature, proving that it can be a simple and reliable tool for the seismic assessment of existing shear-critical bridge piers.