預力預鑄節塊橋柱耐震設計

Seismic Design of Post-Tensioned Precast Segmental Bridge Column

王華靖(Hwa-Ching Wang)

指導教授 ： 張國鎮

國立臺灣大學/工學院/土木工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.03036

摘要

在過去二十年間，以預鑄工法以縮短橋梁建造工時，已逐漸受到歐美各國的重視。橋梁以預鑄工法建造，除了縮短建造工時之外，亦有避免施工期間發生意外、免除施工期間造成之交通中斷、降低對環境衝擊等優點，且可以確保其品質以及降低橋梁使用年限中之維護費用。但是，目前使用預鑄工法建造的橋梁，大多數位於低地震或無地震的區域，而像美國加州或是台灣等受到高度地震威脅之區域，幾乎無使用預鑄工法建造之橋柱，亦沒有提出相關耐震設計規範或建議。因此，本研究歸納先前對預鑄節塊混凝土橋柱之耐震行為研究，以及地震力折減係數的概念，提出設計建議與流程。
本論文分三部分。第一部分為地震力折減係數的探討，根據先前的研究，預鑄節塊混凝土橋柱的消能容量顯柱低於傳統橋柱，在同地震擾動下，欲達到相同的韌性需求，所使用之地震力折減係數需較傳統橋柱小。本研究利用單自由度非線性動力分析，統計36個國內外地震歷時輸入下的非線性反應，探討預鑄節塊混凝土橋柱所適用的地震力折減係數。本研究之分析中，分別使用雙線性塑性(Bilinear Plastic, BP)與勁度衰減自我復位(Stiffness Degrading Self-Centering, SDSC)的遲滯模型，模擬傳統橋柱與預鑄節塊橋柱的非線性行為。研究結果顯示，為達相同韌性需求，預鑄節塊橋柱之地震力折減係數確實較傳統橋柱為小。根據不同消能容量、韌性需求的SDSC與BP模型所得之地震力折減係數比例，修正現行規範地震力折減係數公式，提出預鑄節塊橋柱地震力折減係數的建議值。
第二部分的內容在於探討預鑄節塊橋柱消能容量與韌性容量。由第一部份的研究結果顯示，消能容量與韌性需求是選擇適當的預鑄節塊橋柱地震力折減係數之重要參數。消能鋼棒在基礎中的脫層長度，可避免鋼筋在反覆載重下的過早疲勞破壞，發展預鑄節塊橋柱的韌性容量，本研究提出為達到韌性需求，所需要的消能鋼筋脫層長度。而預鑄節塊橋柱所使用的消能鋼筋比，將會影響其消能容量，為探討其關係，本研究以有限元素分析軟體ABAQUS的有限元素模型，進行一連串的參數分析。掌握消能容量與韌性容量後，在預鑄節塊橋柱的設計中，即可選擇適合的地震力折減係數。
最後一部分為設計範例，根據本研究分析之結果，提出一套完整的設計流程與範例，可供工程師簡單的方法用以設計預鑄節塊混凝土橋柱。本研究所提出的方法與設計公式經驗證可謂合理，未來可望應用於實際工程。

關鍵字

預鑄 ； 節塊橋柱 ； 地震力折減係數 ； 消能容量 ； 韌性需求 ； 雙線性塑性 ； 勁度衰減自我復位 ； 消能鋼棒 ； 脫層長度

並列摘要

Over the past 20 years, the use of the precast modulus construction for accelerating bridge construction has gained attention increasingly in the U.S.A and Europe. Besides the acceleration of bridge construction, the precast modulus construction has advantages to prevent accident occurred, reduce traffic disrupt, and reduce impact to the environment, to ensure the construction quality and to minimize the life-time cost. However, most of the applications have been in the low-seismicity regions. In high-seismicity regions such as California in the U.S. or Taiwan, there is nearly no application or design code provided. Therefore, the behavior study of precast segmental bridge column and the concept of strength reduction factor are attributed in this study to carry out the design recommendation.
There are two parts in this study. The first one is the investigation of strength reduction factor. From the previous study, 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 codes.
The second part is the investigation of energy dissipation and ductility capacity of precast segmental bridge column. According to the first part result, energy dissipation capacity and ductility capacity are crucial to select the appropriate strength reduction factor for precast segmental bridge column. The unbonded length of energy dissipation bar can be used to prevent the energy dissipation bar from premature fracture, and the ductility demand can develop. In this study, the unbonded length used to achieve the ductility demand was carried out. The amount of energy dissipation bar ratio used in precast segmental bridge column effects the amount of energy dissipation capacity. To investigate the relationship, a sequence of parametric analysis is processing in finite element model constructed by the finite element analysis software ABAQUS. After the energy dissipation capacity and ductility capacity are specified, the strength reduction factor can be selected properly in design of precast segmental bridge column.
The last part is design example. Depending on the analysis result of this study, a complete design procedure and a design example are proposed, which provide engineer with a simple method to design precast segmental bridge columns. The procedure and equation for designing purpose are verified to be reasonable. It may be applicable in practical engineering cases in the future.

並列關鍵字

precast ； segmental bridge column ； strength reduction factor ； energy dissipation capacity ； ductility demand ； bilinear plastic ； stiffness degrading self-centering ； energy dissipation bar ； unbonded length

參考文獻

1. 王瑞禎，指導教授：張國鎮、陳振川，「預鑄節塊橋柱試驗及行為研究」，博士論文，國立台灣大學土木工程學研究所，7月，2005。

8. 歐昱辰, 蔡木森, 王華靖, 張國鎮. (2009). “預鑄節塊橋柱的地震力折減係數.” 結構工程期刊.（已接受）

9. Yu-Chen Ou, “Precast Segmental Post-Tensioned Concrete Bridge Column for Seismic Regions”, the thesis of PhD of State University of New York at Buffalo, June 2007.

10. Sarah L. Billington, Robert W. Barnes, and John E. Breen, “A Precast Segmental Substructure System for Standard Bridges”, PCI Journal, Vol. 44, No. 4, July-August 1999, page 56-73.

11. Wing-Pin Kwan, A.M.ASCE, and Sarah L. Billington, A.M.ASCE, “Unbonded Post-tensioned Concrete Bridge Pires. I:Monotonic and Cyclic Analyses”, Journal of Bridge Engineering, Vol. 8, No. 2, March 1, 2003.