Local compressive length of post-tensioning concrete wall

Abstract

Post-tensioning (PT) concrete wall system is one of the well-developed seismic resilient structures due to its low damage, repairability and small residual deformation. Local compressive length defined as the length where concrete compressive strain concentrate is critical to estimate the strain and design the confining stirrups at the wall toe, yet the strain distribution and its localized height haven’t been studied theoretically and systematically. A 2D finite element model implemented in VecTor2 was first developed for PT wall analysis to study its local compressive mechanism at the wall toe. The model was verified by comparison of global and local responses with previous experimental results. Parametric study was conducted to investigate the most critical factors influencing the local compressive length of PT walls. Results show that the compressive length is significantly correlated with axial load ratio and shear span ratio. A new formula considering these influencing factors was proposed and compared with the previous empirical formulas. Results show that previous empirical formulas overpredict the local compressive length and underestimate the corresponding compressive strain, while the proposed formula can accurately estimate both local compressive length and strains. The wall designed with the proposed formula performed significantly better than walls with previous formulas. Design recommendations are provided regarding the calculation methods for critical strain at the wall toe and the height for confinement stirrups. The research output compensates for the lack of theory about local compressive mechanisms of PT walls and provides theoretical support for confinement design.