Improved estimation of the reverse-cyclic behavior of fully-grouted masonry shear walls with unbonded post-tensioning

The use of unbonded post-tensioning to develop fully-grouted masonry shear wall systems that can respond by rocking has recently gained significant momentum. The behavior of these walls has been routinely characterized using monotonic analysis with primary consideration to the rocking mechanism, concentrating the wall deformations at the base. However, experiments have indicated that these walls experience noticeable flexure and shear responses, in addition to rocking, which has been inadequately addressed by previous analysis methods. Moreover, when these walls are subjected to reverse-cyclic loads, their initial post-tensioning forces may reduce significantly due, in part, to masonry degradation at the wall base, producing responses that cannot be captured accurately using monotonic analysis. This paper presents an analysis method that can address these issues by accounting for the reverse-cyclic loading and the three mechanisms of rocking, flexure, and shear. Rocking is estimated using inelastic fiber-element sectional analysis at the wall base, while flexure and shear are modelled as elastic mechanisms, assuming they are small components of the total wall responses. The proposed method is evaluated using experiments and finite element analyses of fully-grouted masonry shear walls with unbonded post-tensioning. The method adequately captures the experimental force-displacement responses, hysteretic energy dissipation, and displacement component responses of the walls. Estimation of the post-tensioning forces experienced by the walls is significantly improved compared to monotonic analyses.