消能鋼筋對預力預鑄混凝土節塊橋柱之耐震行為影響

Abstract

本研究主要探討消能鋼筋對於預力預鑄節塊橋柱耐震行為的影響與PISD 3D模型分析，研究中總共有三組試體，其中試體2及3為本研究中所規劃的二組試體，試體1由四個節塊所組成，不含任何消能鋼筋，試體2在第一節塊與基礎之間設置四根消能鋼筋，消能鋼筋比為 ，試體3在第二節塊與基礎之間設置四根消能鋼筋，消能鋼筋比為 ，在三組試體中比較消能及塑鉸行為的差異，並建立24組變化參數的模型以探討消能鋼筋比、初始預力量以及柱的高寬比對於預力預鑄節塊橋柱耐震行為的影響。 本研究結果顯示：(1)利用力學平衡之聯立方程組來分析橋柱耐震行為，可獲得良好的預測結果。(2)此種橋柱第一節塊底部與第二節塊底部塑鉸長度隨著側位移而改變，並與消能鋼筋握裹位置有關。(3)橋柱安裝消能鋼筋能有效提高試體遲滯消能能力，試體1的遲滯阻尼比為 ，試體2及3則分別提升至 、 。(4)利用PISD 3D模型所做的參數研究，發現本研究橋柱試體在消能鋼筋比 之下，橋柱的遲滯阻尼比能提升至 ，並仍然保有自行復位的能力，在消能鋼筋比 之下，橋柱雖然擁有最高的遲滯阻尼比 ，但已經開始有明顯的殘餘變形產生。

This study presents experimental and analytical results of post-tensioned precast concrete segmental bridge columns using energy-dissipating (ED) bars. Three ungrouted post-tensioned, prescast concrete-filled tube segmental bridge column specimens were designed and tested. All specimens were composed of a load stub, a footing, and four circular segments post-tensioned with internal unbonded high-strength strands. Moreover, Specimen 2 had four ED bars anchored between the first segment and footing, and Specimen 3 had four ED bars anchored between the second segment and footing. The effects of different anchoring position on segment opening and energy dissipation could be examined. In all specimens, the ratio of ED bar area to cross-sectional area of the segment, □, was 0.66%. A correlation study was conducted on the test specimens using the computer program PISA 3D. The objective of the analysis was to perform a parametric study on 24 post-tensioned bridge columns, verifying the effects of the ED bar area, initial strand force, and column height-width ratio on the cyclic behavior.

The test results showed that (1) the ED bar could increase energy dissipation in the hysteresis response, and Specimens 1-3 had the equivalent viscous damping ratio of 6.5-8.8%, and (2) plastic hinge length in the first or second segments varied with anchoring position of ED bars and lateral displacement. The parametric study showed that when the bridge column had □=1.2%, the equivalent viscous damping ratio was increased to 12% with zero residual drift. When the bridge column had □=2.4%, the equivalent viscous damping ratio was 14.8%, and the bridge column showed residual drift of 3.12% after reaching 6% peak drift. A design procedure was proposed based on the experimental and analytical studies.