鋼骨鋼筋混凝土柱軸向載重行為研究

Abstract

本研究旨在以試驗的方式，藉著十根包覆型鋼骨鋼筋混凝土(SRC)短 柱試體在軸向載重 下的破壞行為，探討鋼骨斷面形狀、鋼骨含量、 箍 筋間距、箍筋形狀以及箍筋含量等試體 變化參數對於SRC柱之極限強度 、圍束效應以及極限載重後剩餘強度的影響。 實驗結 果顯示，試體受軸向載重時，先有一段頗為線性之行為，之後則顯示出非 線性 之關係而達到極限載重；混凝土保護層則開始有明顯的剝落，進 而主筋的挫屈與箍筋錨定 的破壞或斷裂伴隨而至，圍束混凝土亦有部 份的剝落。此些破壞為SRC柱典型的破壞模式。 ! 研究結果顯示內含 十斷面形狀鋼骨的試体或箍筋間距的縮小，都可以提高圍束效應， 而 此時若間距不變而增加為雙箍筋，則對柱極限強度並無明顯之影響。試體 達到極限載重 後初期的剩餘強度值，則以內含十斷面形狀鋼骨的試體 表現為最佳。相較於四角形箍筋， 八角形箍筋可以有效地改良箍筋間 距不足或鋼骨形式不良所造成之剩餘強度的損失，隨著 箍筋間距的減 少，八角形箍筋的效率將更為提高。 最後，以理論的方法並藉著試驗資料，推導數學計算式，以合理地預測 SRC柱圍束區內 混凝土軸向極限強度提昇的程度，進而應用於SRC柱軸向 極限強度的計算 This experimental research is conducted to investigate the behavior and load-carring capacity of steel reinforced concrete (SRC) columns which are the type of concrete-encased steel columns. Ten specimens are fabricated and testedunder pure axial load. Parameters such as the shape of steel section, contents of steel, spacing of lateral tie, contents of tie and shape of tie, are studiedfor the effect on behavior and capacity, such as ultimate strength, effect of confienment and post-failer strength. Test results show that the specimens behave linearly at the beginning of the test and , then, nonlinearly until reaching the ultimate strength. Concrete cover begins to spall and the buckling of the rebars as well as the fracture of the ties or the failure of anchorage are followed. The small spacing of ties can enhance the effect of confinement. Steel of cross shape behaves well after reaching peak-load and has a higher residual strength. Compared to quadrangled ties, octagonal ties can effectively improve the post-failure strength and avoid the loss of post-failure strength caused by unsuitable steel shape or large spacing of ties. With the decreasing of tie spacing, octagonal tie works more effectively. Based on test results, theoretically develop the procedure to estimate the concrete compressive strength for the concrete highly confined by steel shape. The calculation of axial strength of SRC columns considering the confined concrete compressive strength can predict well.