Research and Applications of Post-Tensioned Precast Segmental Concrete Bridge Columns for Seismic Regions
Date Issued
2011
Date
2011
Author(s)
Tsai, Mu-Sen
Abstract
Precast concrete bridge construction has been proved to be an efficient solution in accelerating bridge construction and minimizing traffic disruption. However, due to concerns with the seismic performance of such type of construction, its application in seismic regions is limited. Therefore, many experimental and analytical studies were conducted. From their results, the seismic behavior of precast segmental bridge column possessed excellent ductility capacity that was adequate for use in regions of high seismicity. In order to improve the serviceability and constructability, a new material named high performance (HP) steel reinforcing bar was applied into the joint of precast segmental bridge column as energy dissipation bar and the cyclic behavior of precast segmental concrete bridge columns with high performance (HP) steel reinforcing bars as energy dissipation (ED) bars were investigated. The HP steel reinforcing bars are characterized by higher strength, greater ductility, and superior corrosion resistance compared with the conventional steel reinforcing bars. Three large-scale columns were tested. One was designed with the HP ED bars and two with the conventional ED bars. The HP ED bars were fully bonded to the concrete. The conventional ED bars were fully bonded to the concrete for one column, whereas unbonded for a length to delay fracture of the bars and to increase ED for the other column. Test results showed that the column with the HP ED bars had greater drift capacity, higher lateral strength, and larger ED than that with fully bonded conventional ED bars. The column with unbonded conventional ED bars achieved the same drift capacity and similar ED capacity as that with the HP ED bars. All the three columns showed good self-centering capability with residual drifts not greater than 0.4% drift. An analytical model referred to as joint bar-slip rotation method for pushover analysis of segmental columns with ED bars is proposed. The model calculates joint rotation from the slip of the ED bars from two sides of the joint. Good agreement was found between analytical predictions and the envelope responses of the three columns
In addition, in order to reduce the seismic demand of precast segmental bridge column, seismic isolation system was applied to precast segmental bridge column and a large scale experimental study was conducted. The test results showed that isolated precast segmental bridge column system can reduce the acceleration of superstructure effectively. Therefore, reducing the shear demand and avoiding the damage of substructure. The benefit of using isolated precast segmental bridge column is that even isolation displacement demand is more than its capacity, precast segmental bridge column can deform more than 3% drift without sever damage. In other words, isolated precast segmental bridge column system has a capacity of large deformation and self-centering.
The energy dissipation capacity of precast segmental bridge column is smaller than that of traditional bridge column. Under the same earthquake excitation, the strength reduction factor for precast segmental bridge column should be smaller than that for traditional one to achieve the same ductility demand. In this study, nonlinear dynamic SDOF analysis was involved, and 36 different ground motions were used in this analysis to investigate the proper strength reduction factor for precast segmental bridge column. In the analysis, bilinear plastic (BP) hysteretic model and stiffness degrading self-centering (SDSC) hysteretic model were used to present the behavior of traditional bridge column and precast segmental one, respectively. According to the result, it was proved that the strength reduction factor of precast segmental bridge column is smaller than that for traditional one. The ratio of strength reduction factor for SDSC model with different energy dissipation capacity and different ductility demand to that for traditional one was meshed up to modify the strength reduction factor formula provided in current seismic design code. Finally, a rational design method was proposed and verified.
Subjects
precast segmental bridge column
strength reduction factor
energy dissipation capacity
ductility demand
unbonded length
stiffness degrading self-centering
energy dissipation bar
isolation
Type
thesis
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