Dynamic test evaluation of numerical models for unbonded post-tensioned concrete walls

Abstract

Post-tensioned precast concrete walls can provide a low-damage seismic resisting system through the use of a controlled rocking mechanism. Seismic analysis of buildings with post-tensioned concrete walls requires accurate estimation of this controlled rocking response. However, only a limited number of laboratory experiments have been conducted to investigate the dynamic response of post-tensioned walls and numerical models have typically been validated against only pseudo-static cyclic test data. Recently conducted cyclic and dynamic tests of single post-tensioned concrete walls have provided a unique opportunity to study existing numerical models. Two types of numerical model were developed to represent the single unbonded post-tensioned concrete wall. A lumped plasticity model was developed using Ruaumoko while a multispring macro model was developed using OpenSees. Both models accurately captured the overall cyclic response of the post-tensioned wall specimens, although only the multispring macro model explicitly included the uplift and rocking mechanism at the wall base. In addition to the overall responses, comparison of the two models against the dynamic test data focused on the different sources of energy dissipation that occur when the wall rocks. Existing techniques for incorporating the energy dissipation of an unbonded post-tensioned precast concrete wall into numerical models were evaluated. The combination of friction and viscous damping to represent the energy dissipation in an isolated unbonded post-tensioned concrete wall shows promising results.