本研究採用AISC-LRFD-2010與非線性之纖維元素法(fiber element method)建立矩形鋼管混凝土柱(Concrete-Filled steel Tubular, CFT)的軸力-雙向彎矩互制曲面。研究中採用的纖維元素法是將構材斷面離散化為數個纖維元素，在固定軸壓力與中性軸轉角下假設偏心軸壓力作用，根據鋼骨與混凝土之應力與應變關係，求得斷面各纖維元素的應力狀態，並逐步調整中性軸位置，直至斷面內力滿足力平衡條件和指定之中性軸轉角為止，即可求得固定軸壓下之兩向彎矩強度，改變軸壓力與中性軸轉角重複計算上述步驟，直至三維軸力-雙向彎矩互制曲面完整。
利用多組矩形CFT軸力-彎矩的試驗數據，驗證纖維元素法用於矩形CFT構材之軸力-雙向彎矩互制曲面的合理性，並討論柱長、寬厚比與材料強度等參數對於CFT柱彎矩強度之影響，定義纖維元素法可使用的範圍。纖維元素法的主要缺點在於無法考慮P-二次彎矩、構材長細比和局部挫屈的影響，目前纖維元素法的軸力-雙向彎矩互制曲面適用於低軸壓之矩型結實短柱。

This study presents nonlinear fiber element analysis method determine the axial load-biaxial bending moment interaction curve of concrete filled steel tubular section (CFT). Fiber element method transform a column section into several fiber elements. Assuming an eccentric shaft of the pressure, according to the stress and strain relationship of steel and concrete, finding stress for each fiber, as well as adjusting the depth and orientation of the neutral axis in a composite section to satisfy equilibrium conditions. Then, it can calculate the axial load and biaxial bending moment.
In this study, discussing bending moment strength compares fiber element method with experience data. Column length, materials strength and thickness ratio are important parameters to reduce the strength of the numerical analysis. The main disadvantages of fiber element method is unable to consider P- effect、slenderness ratio and local buckling. Compact section or non-compact section is an important index having priority to check before analysis. So, fiber element analysis method is applied to analyze short columns and compact-section.
Using axial load and moment experience data of CFT discusses accuracy of AISC-LRFD-2010.

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