鋼筋混凝土梁滑移剪力設計之研究

Study on the sliding shear design for reinforced concrete beams

王勇智(Yung-Chih Wang) ； 郭育廷(Yu-Ting Kuo)

《結構工程》 35卷4期 (2020/12) Pp. 19-35

https://doi.org/10.6849/SE.202012_35(4).0002

摘要

本研究繼先前研究New RC梁設計，乃利用T擴頭鋼筋進行塑鉸外移設計時，雖有成功產生塑性鉸轉移，但卻有明顯垂直於梁向之滑移剪力裂紋發生；而塑性鉸區發生在傳統柱面時、或預鑄RC梁冷接縫在塑性鉸區時，亦有可能有類似滑移剪力裂紋破壞，因此引發本研究主題產生。故本研究主要目的是探討一般RC梁構件受震中，對於可能有潛在滑移剪力（sliding-shear）破壞RC梁，如何檢查以及設計梁斜向鋼筋，以利抑制垂直剪力滑移破壞產生。本文主要先收集先前計畫New RC梁與相關文獻一般RC梁之耐震測試數據，以統計方法檢核紐西蘭規範NZS 3101-2006判斷梁塑鉸區可能發生滑移剪力破壞規定之正確性。其結果為，建議以斷面剪應力0.25√f_c^'（MPa）作為滑移剪力破壞之判別，且較適用於長跨梁（a/d≧2.5）。再者，對於梁構件塑性鉸區有潛在垂直滑移剪力裂縫產生時，則應考慮增設梁斜向鋼筋於塑性鉸區域，以利有效抑制此滑移剪力裂紋產生。本文亦參考其規範在斜向筋設計規定，以實驗作印證；結果為有加入斜向鋼筋RC梁，除了可以抑制垂直梁向滑移剪力裂縫發生外，亦可增進構材耐震性能。最後，綜合紐西蘭規定及本研究結果，乃建議一般跨度RC梁是否要設計斜向鋼筋之設計流程，以供參考。

關鍵字

New RC梁 ； 塑性鉸區 ； 塑鉸外移設計 ； 滑移剪力破壞 ； 斜向鋼筋

並列摘要

This study follow up the previous research on the hinge relocation design by using T-headed bars. The main conclusion is that the T-headed bars as extra reinforcement can successfully relocate the plastic hinge zone from the column face to a distance away from the face, however the final failure mode of sliding shear occurred. The similar sliding shear failure could be also found in the plastic hinge zone occurred at the traditional column face, or in the precast cold connection located in the plastic zone. Therefore, the main purpose of this study is to discuss how to design the diagonal reinforcement of the beam to prevent the occurrence of vertical sliding shear cracks for the general RC beam members subjected to the major earthquake. This article mainly collected the tested beams subjected seismic loading to verify the design of the sliding shear specified in the NZS 3101-2006. It was concluded that the sectional shear stress , 0.25√f_c^'(MPa), to check the potential sliding shear failure occurred in the plastic zone of RC beams is suitable for normal-span beams (a/d≧2.5). Therefore, if the potential vertical sliding shear cracks may be occurred in the plastic hinge zone of RC beams, the diagonal reinforcement shall be considered. Meanwhile, the cyclic testing performed comparing two types of beams between with and without diagonal bars repealed that the RC beams with diagonal bars can prevent the sliding shear cracks from occurring, and improve their seismic resistance. The design flow chart for prevention of sliding shear failure occurred in RC beams is finally suggested in the paper.

並列關鍵字

New RC ； plastic hinge ； hinge relocation design ； sliding shear ； diagonal reinforcement