Feasible region of post-tensioning force for precast segmental post-tensioned UHPC bridge columns

Abstract

This paper aims to establish an analytical method to determine the feasible region of post-tensioning (PT) force for precast segmental post-tensioned ultra-high performance concrete (UHPC) bridge columns. Three principles, i.e. no collapse after earthquake, good self-centering capacity, and no shear failure at joints, were put forward to define the feasible region of PT force according to the ultimate state. A calculation procedure was developed to determine the ultimate state and verified by a validated finite element model. With the ultimate state known, an analytical method was established to calculate the feasible region of PT force according to the three principles. Parametric analysis was conducted to quantitatively study the effects of eight common design parameters on the feasible region of PT force. A noniterative calculation method was further given to determine the feasible region of PT force for designers. The results show that the calculation procedure can accurately predict the characteristic values at the ultimate state. There are significant effects of the eight design parameters on the feasible region of PT force, which is actually controlled by the two former principles. The gravity loading can provide sufficient shear resistance at joints without shear keys in general. The feasible region of PT force is mainly distributed between 0.10 and 0.20 for precast segmental UHPC bridge columns with an area ratio of energy dissipation (ED) bars of more than 1.00%. The feasible region of PT force does not exist when the ED bar ratio is more than a critical value (i.e., 2.83% in this research). A noniterative and conservative calculation method to determine the feasible region of PT force can be obtained when the compression zone height of the bottom section at the ultimate state is equal to the wall thickness of the hollow section.