Two-plastic-hinge and two dimensional finite element models for post-tensioned precast concrete segmental bridge columns

摘要

Recent studies have confirmed that unbonded post-tensioned (PT) precast concrete segmental bridge columns are capable of undergoing large lateral deformation with negligible residual drift. To provide a clear guideline for the modeling of the columns for practicing engineers as well as researchers, this paper presents two types of numerical models: (ⅰ) a two-plastic-hinge model using the sectional moment-curvature analysis procedure at two segment interfaces and (ⅱ) a two-dimensional (2D) finite element model using truss and beam-column elements in the computer program PISA. Three unbonded PT precast concrete-filled tube segmental bridge column specimens are cyclically tested. Two specimens have mild steel bars crossing to different column heights for studying the effects of anchorage position on the hysteretic energy dissipation (ED) capacity. The test results show that (1) the mild steel bars ("ED bars") can increase hysteretic energy dissipation, and Specimens 1 -3 have equivalent viscous damping of 6.5-8.8%, (2) a plastic hinge length in the first or second segment varies with anchorage position of ED bars and lateral displacement, and (3) an equivalent unbonded length along which the strain in the ED bar is assumed uniformly distributed on each of the two sides is 5-6 bar diameter. A 2D finite-element model is utilized to predict the cyclic behavior of the specimens. Parametric studies using finite-element models are also conducted to investigate the effects of ED bar area, initial strand force, and aspect ratio on the cyclic behavior.