Seismic tests on precast segmental concrete columns with unbonded tendons

Four unbonded post-tensioned precast segmental concrete columns were subjected to pseudostatic simulated lateral seismic loading in the Charles Lee Powell Structural Research Laboratories at the University of California at San Diego. The influence of parameters including steel jacket confinement, prestress level, and column aspect ratio on column force - deformation characteristics, energy dissipation, damage level, and failure mode was studied. To investigate prestress influence and damage repairability, each column was tested twice: the first test with a given prestress level and a second test, subsequent to column repair, with higher initial prestressing. Shear keys were not provided at segment interfaces, and thus shear was transferred by a friction mechanism. Ductile flexural response was observed in all tests, and maximum column drift levels of 4 - 6% were achieved. Damage included minor concrete crushing at the interface of column and footing, steel jacket inelastic straining, and residual drift on the order of one-half per cent. Key test results are compared to those predicted by a simple analytical model and good agreement is observed. It is concluded that this structural system can be designed to resist severe seismic demands while offering the benefit of reduced post-earthquake damage and the associated economic loss.