大號鋼筋(D43、D57)混凝土受軸拉及偏心拉拔之握裹行為研究

Axial and Eccentric Pull-out Behavior of Large-size Steel Bars in Concrete

林家宏(JIA-HONG LIN)

指導教授 ： 干裕成

朝陽科技大學/理工學院/營建工程系/碩士(2013年)

摘要

本研究主要在透過握裹試驗，探討混凝土與各號鋼筋間之握裹力學行為；並對混凝土保護層與有裂縫產生之混凝土間之力學行為進行研析。同時，本研究試驗中並輔以音射法進行力學行為監測，且利用有限元素法ANSYS之數值模擬分析。
由試驗發現，在相同混凝土強度中，鋼筋直徑越大，愈小，且鋼筋的極限握裹應力也著鋼筋的直徑增加而降低。在本研究中，每側保護層10 cm之軸拉試體與一邊保護層減少5cm之偏心拉拔試體之混凝土握裹強度接近，對鋼筋應力的發展，影響不大。預裂偏心試體應力皆明顯小於偏心拉拔試體，顯示混凝土保護層出現裂縫時，其混凝土與鋼筋間的握裹力變差。由有限元素法之應力分析，可知最大主應力及最大剪應力會隨著保護層與鋼筋直徑比(c/d)而遞減，此趨勢與實驗所得之平均握裹強度，完全一致。由趨勢迴歸分析可得知，偏心試體之握裹強度隨鋼筋直徑增大之折減率，較軸拉試驗為大。

關鍵字

有限元素 ； 偏心 ； 拉拔

並列摘要

This research attempts to investigate the bond behavior between concrete and rebar in various sizes through the pull-out test. In addition, bond behavior between the rebar and pre-cracked concrete is also investigated. Meanwhile, the acoustic emission (AE) was employed during the test for monitoring the cracking of concrete and of a finite element analysis via ANSYS was conducted in this research. From the test results, it showed that for the same concrete strength, the ultimate pullout force increases, but the ultimate bond strength decreases as bar diameter increases. The concrete cover reduced from 10 cm to 5 cm in one side of the concrete cube made little difference in bond strength as well as the stress in rebar as de-bonding. Pre-cracked eccentric pullout concrete shows less than bond strength than those without pre-cracking. It implies that the existence of crack decay in the bond between rebar and concrete. From the finite element analysis, it showed the maximum principal stress and the maximum shear stress decreases with the increase of the ratio of cover-to-bar diameter (c/d), which consisted with the nominal bond strength observed from the test results. From a regression analysis, it showed that the deduction of bond strength for the eccentric specimen is larger than those axial as the rebar diameter increase.

並列關鍵字

Ansys ； Pull-out ； Eccentric

參考文獻

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