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  • 學位論文

預力混凝土梁桁架化之非線性行為研究

A Study on Nonlinear Behavior for Trussliezd Prestressed-Concrete Beam

指導教授 : 陳清泉

摘要


預力混凝土構件係在普通鋼筋混凝土構件受拉側於外載重作用前導入一外加力量,即預力,並藉由該預壓力抵銷若干設計載重造成之拉應力,藉此可抑制裂縫成長、減少撓度,增進耐久性。目前規範對預力混凝土構材所受之應力有諸多限制,除透過載重試驗無法了解預力混凝土構材容許應力後之真實行為之外,尚期以理論方式探討之。 一般鋼筋或預力混凝土結構物皆可區分為2種區域,即B區域與D區域。無論是B區域或D區域,理論上皆可以桁架模型模擬之,其中B區域可以依傳統桁架模型模擬,D區域由相關文獻得知則可使用壓拉桿模型模擬。 本文旨在推求預力混凝土梁之容量曲線。首先將預力混凝土梁轉換成一等值桁架構架。其次由所使用材料之組成律,並依斷面分析程式及本文所假設之方法可分別求得各桿件斷面之軸力-變位關係曲線。再利用SAP2000程式進行結構分析,可求得各桿件受軸力狀況,然後酌量放大梁頂載重,當構架進入非線性階段後,假設儲存於構架內之總應變能不變,仍依能量守恆原則之擬彈性法進行分析,將模擬構架中各桿件超出軸力彈性範圍之能量轉換成塑性能量,進而求得近似構架之非線性行為,包括構架之極限承載力及其中間點之最大變位等,以了解預力梁之容量曲線。 經本文實例分析研究之後,均可獲得良好之行為結果,可以驗證本文桁架化擬彈性之結果,具其良好之準確度。

並列摘要


Prestressed concrete elements are defined as reinforced concrete elements subjected to outer compressive force in tension side prior to loads acting on them. The force can neutralize amount of tension stress caused by designed loading, refrain the growing cracks, decrease the deflections, and increase the permanency, etc. Due to several stress limitations to prestressed concrete elements in provisions, it is difficult to realize the real behavior of prestressed concrete elements beyond the permission stressed stage without loading test. Prestressed concrete and reinforced concrete elements can be divided into two categories: B region and D region. Both of which can be simulated as truss model. The objected of this paper is to analyze the capacity curve of prestressed concrete beams(PCBs). Firstly, the PCBs have to be transformed to the equivalent trusslized models. Secondly, sectional axial force-deformation curve of each bar can be both obtained by using sectional analytical program with the stress-strain relation of material and proposed simulated approach in this paper. Thirdly, the structure will be linearly analyzed by adopting SAP2000 software, and the member forces can be carried out. When the structure load is gradually increased, the structure behaves into nonlinear stage, and the Pseudo-elastic method is applied to transfer the energy exceeding the elastic range into plastic energy. Finally, the nonlinear behavior of simulated structure concluded the ultimate vertical forced, the maximum deflection of middle of beam can be analyzed and compared the results with real test curved to check their matching conditions. After four PCBs analyzing in this study, the simulated capacity curve can be well obtained to show that PCBs trusslized pseudo-elastic method is an acceptable and applicable method.

參考文獻


[3] AASHTO, LRFD Bridge Specifications and Commentary, 2nd Edition, American Association of State Highway and Transportation Officials, Washington, DC, 1998, 1116, pp.
[1] Schlaich, J., Schäfer, K., and Jennewein, M., “Toward a Consistent Design of Structural Concrete,” PCI Journal, Vol. 32, NO.3, May-June 1987,pp.74-150.
[2] ACI Committee 318, “Building Code Requirement for Reinforced Concrete(ACI318-02)and Commentary (ACI318-02R),American Concrete Institute, 2002.
[4] XTRACT, “Cross Sectional X sTRuctural Analysis of ComponenTs”,Version 3.0.1,2004.
[11] Julio A. Ramirez and John E. Breen, “Evaluation of a Modified Truss-Model Approach for Beams in Shear,” ACI Structural Journal, Vol. 88, No. 5, pp.562-571, 1991.

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