大尺寸鋼筋混凝土梁之握裹能力及撓曲行為

Bond Efficiency and Flexural Behavior of Reinforced Concrete Beam with Large Diameter Steel Bars

陳麗惠(Li-Huai Chen)

指導教授 ： 顏 聰 ； 干裕成

朝陽科技大學/理工學院/營建工程系/博士(2013年)

摘要

本文主要探討大尺寸鋼筋混凝土握裹行為，研究包括兩部分試驗：大尺寸鋼筋( #14、#18 )拉拔試體的拉拔試驗，及配置大尺寸鋼筋梁的撓曲試驗。兩部分試驗都同時考慮設有裂縫的預裂試體。總共製作48個拉拔試體和6支全尺寸鋼筋混凝土梁試體，用以探討大尺寸鋼筋特有的握裹行為與性能，以及鋼筋混凝土梁的撓曲行為、破壞模式和承載能力。
試驗結果顯示，拉拔試體的初裂載重與極限握裹力比值Pcr / Pu都介於48%-64%，不受鋼筋尺寸之影響，但梁試驗極限握裹強度μu及對應之最大拉力端位移δu，則隨鋼筋尺寸的增加而減小；大尺寸鋼筋(#14、#18)的μu及δu的降低幅度特別明顯，意味著此類鋼筋的握裹延展性甚小，其握裹失敗可能提早發生。配置大尺寸鋼筋(#14及#18)的混凝土梁呈現與#10鋼筋梁相似的撓曲反應，但是從降伏點到極限狀態的撓度變形行為則彼此不同，大尺寸鋼筋梁的延展性μ△會大幅折減。這種梁的握裹功能可一直維持到降伏階段，因而得以利用傳統規範方法預測其降伏強度，不過其計算之極限強度則會被高估。

關鍵字

拉拔試驗 ； 大尺寸鋼筋混凝土握裹行為 ； 梁撓曲試驗

並列摘要

This paper attempts to investigate the pollout behavior of large size bar in concrete.This study includes two parts of experiments: Pull-out test and flexural beam test of concrete with large diameter steel bars of No.14 and No.18. Pre – cracked specimens of the both were also investigated in this study. Totally, 48 pull-out specimens and 6 full-scale beams were fabricated and tested to investigate the bond performance, flexural behavior, failure mode, and load capability.
Test results showed that the ratio Pcr / Pu of cracking load Pcr to ultimate bond force Pu of the pull-out specimens falls between 0.48 and 0.64, regardless of the size of steel bar. Whereas, the maximum bond stressμu and the corresponding maximum loaded-end slipδu decrease as the bar diameter increases. This implies that such reinforcements can have only limited bond ductility, which leads to a premature failure of bond. In addition, the reinforced concrete beam with large diameter reinforcing bars exhibits a similar flexural response as the beam with steel bar of No10; however, the ductility of the beam with large diameter bars was found to be greatly reduced. It turned out that the beam could remain fully bonded until yielding stage; thus, it is consequently valid to predict the yielding strength with conventional code method. Nevertheless, their calculated ultimate strength was found to be overestimated.

並列關鍵字

full-scale beams ； Pull-out ； flexural beam test

參考文獻

2. Soroushian , P. , and Choi , K. B., “Local Bond of Deformed Bars with Different Diameter in Confined Concrete,” ACI Structural Journal , No.86-524 , March-April, pp.217-222 , 1989.

3. Ferguson , P.M., and Thompson , J.N., “Developmemt Length for Large High Strength Reinforcing Bars in Bond ,” ACI JOURNAL , Proceedings Vol.59 ,No.7 ,July., pp.887-992 , 1965.

4. Ferguson , P.M., and Thompson , J.N., “Developmemt Length for Large High Strength Reinforcing Bars , ” ACI JOURNAL , Proceedings Vol.62 , No.1 , Jan., pp.71-94 , 1965.

5. Ferguson , P.M., Breen , J.E., and Thompson , J.N., “ Pullout Tests on High Strength Reinforcing Bars ,” ACI JOURNAL , No. 62-55 , pp. 934-949 , August 1965.

6. Ykimasa Goto , “ Cracks Formed in Concrete Around Deformed Tension Bars , ” ACI Journal , Proceedings , Vol.68 , No4 , pp.244-251 ,1986.