在RC結構物中，為能使力量有效的傳遞，鋼筋與混凝土間須有足夠的握裹。然而，影響握裹性能的好壞原因眾多，包含鋼筋表面幾何性質(Rr值，節高節距之比值)、混凝土強度、保護層厚度、箍筋、軸壓力等，均會影響其行為。雖然上述影響因子均有相關研究報告，但大多以單向載重試驗為主，對於握裹在反覆載重下行為較少提及，而處於地震帶之建物經常受到地震帶來之反覆作用影響，勢必對握裹造成損傷，由其對於內部梁柱接頭影響甚大。
有鑒於此，為了瞭解在反覆作用下之基本握裹行為，本研究共進行十二組鋼筋與混凝土於反覆拉拔下握裹測試之試體，並額外製做兩組以單向拉拔之試體，以比較反覆拉拔兩者之差異。本次採用主筋為SD550，混凝土設計抗壓強度均採用35MPa，主要探討變數為埋置長度(20、24、26、28、32、36倍鋼筋直徑)、主筋號數(#8、#10)與軸壓應力比(0.05、0.2)，以了解各項因子對握裹行為表現之影響。本次試驗結果顯示，軸壓應力比自0.05提升至0.2能使埋置長度縮短約10%，並由有限試驗數據經由內插方式求得軸壓力影響方程式。觀察握裹應力對混凝土強度正歸化與滑移量關係圖發現當滑移量超過0.32mm時，握裹將發生較快速的破壞，且測試多組不同埋置長度試體發現，當埋置長度不足時，將發揮較大握裹應力。並將握裹應力容量定義於極限滑移量為1mm時，於軸壓應力比為0.2情況下為1.25倍混凝土抗壓強度0.5次方。因此在僅受拉力情況下，若須確保主筋能強度發揮1.25fy，則埋置長度至少需要24倍主筋直徑。

In the RC structure, the bond performance will be influenced by lots of factors, including geometric of reinforcement (Relative Rib Area, Rr), concrete compression strength, clear cover, transverse reinforcement, axial force. Nowadays, the bonding models are commonly obtained by monotonic loading test. However, in the moment resisting frames, the interior beam-column joint may be critical regions in seismic design.
To understand the basic bond behaviors under cyclic loading, this study carried out fourteen bonding test specimens which use SD550 rebars and concrete design compressive strength is 35MPa, including twelve specimens conducting cyclic tensile loading and two specimens conducting monotonic tensile loading to compare with the result of cyclic tensile loading. This study also explores different anchorage length, size of reinforcement, and axial force to compare the bond performance. The test results show that the anchorage length decreases about 10% when axial force from 0.05Agf'c increase to 0.2Agf'c. From the relation between the slippage and the bond stress correlated with the concrete compressive strength observes a rapid bond deterioration when the slippage over 0.32mm. Additionally, it will develop larger bond stress if the anchorage length is not long enough. In this study, the available bond stress is 1.25 times the square root of f'c which is defined as the slippage at 1mm under 0.2Agf'c. Hence, to make sure longitudinal reinforcements can develop 1.25fy under cyclic tensile loading, the anchorage length is 24 times diameter of longitudinal reinforcement at least.

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