Pseudodynamic Testing and Inelastic Displacement Ratios of Self-Centering Precast Concrete Segmental Bridge Columns

摘要

Three unbonded post-tensioned segmental bridge columns were tested in this research using pseudodynamic loading. The loading consisted of three consecutive ground motions representing two design and one maximum probable earthquakes. Test results showed the columns without energy-dissipation (ED) bars and those with a proper number of ED bars showed minor damage and small residual displacements even after tests with three ground motions. Based on the test results, a new hysteretic model, referred to as modified stiffness-degrading self-centering (SDSC) model, was developed for segmental columns with flag-shape hysteretic behavior. Compared with the original SDSC model, the proposed modified SDSC model includes a set of new reloading rules for reloading occurring within the flag area of the model. The proposed model captured well the response histories of the two columns with flag-shape hysteretic behavior tested in this research. Nonlinear dynamic analyses were conducted to investigate the inelastic displacement ratio (CR) of the proposed modified SDSC model and the modified modified-Clough (modified MC) model (representing conventional columns). Analysis results showed that the CR of the modified SDSC model is always larger than that of the modified MC model. Moreover, it tends to increase with decreasing energy dissipation provided by the ED bars. As a result, the period at which the CR of the modified SDSC model approaches 1 tends to be larger than the modified MC model, or does not approach 1 before the period limit examined in this study (3s) even under far-field (FF) ground motions. The modified SDSC with =4% (self-centering segmental columns without ED bars) is not recommended for use because of the high chance of dynamic instability.