透過您的圖書館登入
IP:44.211.117.101
  • 學位論文

鋼筋混凝土橋柱之新平滑型遲滯模型與容量位移反應譜

A New Smooth Hysteretic Model and Capacity-Based Displacement Spectrum for Reinforced Concrete Bridge Columns

指導教授 : 張國鎮 歐昱辰

摘要


本研究提出一個適用於撓曲破壞控制之鋼筋混凝土橋柱之新平滑型遲滯模型,文中依現行橋梁耐震設計規範設計四座縮尺橋柱試體,該試體具有相同的設計參數但承受不同型式之加載歷程,分別為單向漸增式反復載重、改變振幅式反復載重及真實地震歷時載重,再依對試驗行為之觀察,建構相應於結構性質損傷累積與加載路徑相依特性之遲滯規則。在結構性質損傷累積的模擬方面,勁度衰減與最大位移及累積之遲滯消散能量有關,而遲滯迴圈之束縮(Pinching)嚴重程度則會與殘餘位移成正比,且該殘餘位移必須存在於加載方向之反側才會有束縮效應;此外,強度衰減則會與損傷指標有關,且當損傷指標尚未累積到某一臨界值時,強度衰減並不會發生。在加載路徑相依特性之遲滯規則方面,本研究將加載路徑區分為主路徑與副路徑兩類,其中,主路徑係指該路徑起始於不小於曾經所發生過存在於加載方向反側之最大殘餘位移,而不符合主路徑者則皆歸屬於副路徑,且副路徑皆會指向相依於主路徑之某些特定指向點。此外,在卸載過程中尚未完全卸載前即再行加載,則此再加載之行為可採線性加載至原卸載點;而當結構反應僅於單一方向產生較大之非彈性變形時,其後之反向加載行為需考慮最小勁度衰減以反應真實結構行為。最後,本研究所發展之遲滯模型經與歷經三個接續地震歷時的擬動態試驗結果比對,證實可準確模擬橋柱在真實地震作用下的受震反應。 接著為了以定量化的方式探討不同設計參數對鋼筋混凝土橋柱遲滯衰減行為之影響,本研究由PEER結構性能試驗資料庫及NCREE橋柱試驗資料庫中挑選出合適之試驗資料,藉由不同模型參數可分別描述相應之結構性質衰減程度的特性,針對包含橋柱之主筋比、箍筋比、高寬比與軸力比等主要設計參數之試驗資料進行模型參數識別工作,萃取出相應之模型參數,以瞭解橋柱設計參數對遲滯衰減特性之影響,並採理論解析的方式探究其影響的成因。 最後,本研究採用所提出的平滑型遲滯模型來建置適用於鋼筋混凝土橋柱之非彈性位移反應譜及其相應之損傷狀態譜,以應用於橋梁之耐震能力評估。在反應譜的建構上,係採用前述不同設計參數所識別出之模型參數之單自由度系統,進行非線性動力歷時分析,輸入之地震歷時則分別採用15筆遠域地震及15筆近斷層地震,以考慮震源特性之影響。再者,考量採用本文之遲滯模型在某些地震歷時與結構性質的組合下,特別是強度較低之短週期結構受近斷層地震時,會產生倒塌破壞的情況,故需事先定義結構系統層面與平均值反應譜層面之破壞準則,以利反應譜之建置。而所建置的反應譜除了可用來探討不同橋柱設計參數與震源特性的影響外,亦可用檢驗文獻上著名非彈性位移係數公式之適用性。最後,本研究亦提出非彈性位移係數與相應損傷狀態之公式,其可考慮不同結構週期、強度係數、設計參數與震源特性之影響。

並列摘要


A new smooth hysteretic model was proposed for ductile, flexural-dominated reinforced concrete bridge columns. Four identical columns designed per modern seismic codes were tested using monotonically-increasing and variable-amplitude cyclic loading protocols and ground motion loading to develop the model. Based on the observations from the test results, hysteretic rules for damage accumulation and path dependence of reloading were constructed. For damage accumulation, stiffness degradation is correlated with the maximum displacement and hysteretic energy dissipation, while pinching severity is related to the residual displacement in the direction opposite to the loading direction. Strength deterioration is correlated with the damage index and does not occur until the damage index reaches a threshold. For path dependence of reloading, reloading paths are classified into primary paths and associate paths. The primary paths are those that start from a residual displacement that is equal to or larger than the previous maximum one. The associate paths are those that do not belong to primary paths and tend to be directed towards certain points. Reloading without load reversal is assumed to be linear and a minimum stiffness degradation is needed after significant yielding in one direction. Comparison with the results of pseudo-dynamic tests using three consecutive ground motions showed that the proposed model closely matched the test results. To quantitatively investigate the effects of various design parameters of RC bridge columns on deteriorated hysteretic behavior, model identification for various test results was conducted. The considered design parameters includes the ratios of longitudinal reinforcement and transverse reinforcement, aspect ratio, as well as axial load ratio of columns. Test data focusing on these effects was mainly obtained from the structural performance database by PEER and the NCREE bridge columns database. For each of the tested columns, model parameters capable of representing different deterioration characteristics of structure properties were identified. Furthermore, the cause of differences between the identified model parameters from different design parameters of column was also discussed theoretically. In addition, inelastic displacement spectra associated with corresponding damage state for RC bridge columns were constructed using the proposed hysteresis model to facilitate seismic evaluation. Nonlinear time history analysis for SDOF systems having different hysteretic behaviors identified from the tested columns with various design parameters and subjected to 15 far-field and 15 near-fault pulse-like ground motions was conducted. Failure criteria was made because columns analyzed by the proposed model could fail under one or more than one of the earthquake records especially when subjected to near-fault ground motions. Furthermore, the effects of various design parameters of column and earthquake types on the computed spectra were presented and the well-known inelastic displacement ratio formula in the literature were evaluated using the computed spectra. Finally, formulae for inelastic displacement ratio and corresponding damage state as a function of structural period, strength ratio, and various design parameters were established for far-field and near-fault ground motions, respectively.

參考文獻


[1]. Seismic retrofitting manual for highway bridges, Federal Highway Administration FHWA, 2006.
[2]. Guide specification for LRFD seismic bridge design, American Association of State Highway and Transportation Officials AASHTO, 2011.
[5]. Eurocode 8 - Design of Structures for Earthquake Resistance - Part 2: Bridges. The European Standard EN 1998-2, 2005.
[6]. OpenSees. Open System for Earthquake Engineering Simulation. Available online; http://opensees.berkeley.edu.
[8]. Takeda T, Sozen MA, Nielson NN. Reinforced concrete response to simulated earthquakes. ASCE Journal of the Structural Division 1970; 96:2557-2573.

延伸閱讀