本論文針對超高強度填充型箱型柱進行試驗，主要探討的課題為斷面強度、肢材寬厚比的影響、軸向延展性、局部挫曲變形及內部填充混凝土之行為。共完成18支大尺寸填充型箱型柱。鋼板使用標稱強度為5.6 tf/cm^2之HT690鋼材，混凝土抗壓強度為0.56tf/cm^2 、0.70tf/cm^2 兩種，箱型柱斷面寬度介於255至480 mm之間，鋼板厚度為8、10、15 mm等三種，長寬比為1.0、1.3、1.9三種，肢材寬厚比則介於24至48共5種。
研究結果顯示：（1）填充型箱型柱在發展出最大強度後，強度將快速下降，此現象為內部混凝土強度急遽下降導致，肢材寬厚比越大的試體，下降的幅度將越大。（2）當5.6tf/cm^2 級之箱型鋼柱搭配0.56tf/cm^2級以上之混凝土時，AISC規範之設計公式會出現高估強度的現象。（3）斷面長寬比越大的箱型柱，在拱效應的作用之下，內部的圍束混凝土行為越差，此現象在弱軸承受彎矩時將會更加顯著。

This paper presents experimental study on the behavior of concrete-filled box columns (CFBC). A total of 18 specimens, including 14 square box columns and 4 rectangular box columns were tested under axial loading. All specimens were fabricated form high strength materials ( Fy= 5.6 ; f'c = 0.56 and 0.70 ). The primary test parameters were the width-to-thickness ratio (B/t ), cross-section aspect ratio (B/D ) and the nominal compressive strength of concrete (f'c ). Steel plate thicknesses used were 8 to 15 mm and the section widths used were 255 to 480 mm. Width-to-thickness ratio of the section ranged from 24 to 48 and the cross-section aspect ratio ranged from 1.0 to 1.9.
Experimental results show that: (1) The strength of CFBC specimens rapidly decreased as it reached to the peak loading. The primary reason was due to the strength of concrete which deceased suddenly. The higher b/t ratio was, the faster the decreased speed was. (2) AISC code might overestimate the strength of CFBC when fabricated from steel plates with Fy = 5.6 and concrete with f'c = 0.56 and 0.70 . (3) Owing to the horizontal arch action, confined concrete in the CFBC performed poorly while the B/D ratio was higher then 1.0.

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