截面预裂的RC构件直剪与斜剪承载力比较*
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（同济大学土木工程学院建筑工程系， 上海 200092）［摘要］钢筋混凝土构件截面中若存在与剪力方向平行的裂缝，则构件的直剪承载力显著降低。目前我国规范未进行直剪设计或验算，可能存在安全隐患。为说明此问题，进行了试验和分析研究。设计22个具有不同的贯通裂缝长度、直剪配筋率和直剪钢筋位置的Z形试件，得到了其直剪极限承载力。结果显示，直剪极限承载力随裂缝长度的增大而减小，但基本不受钢筋布置位置的影响。采用分析的方法并考虑可靠度近似一致，获得了与直剪面具有相同材料和几何特征但不同配箍率的构件斜剪极限承载力。在极限承载力和承载力设计值两个层面上，比较直剪和斜剪承载力。研究发现，若截面存在贯通裂缝、箍筋配筋率较大（大于0.18%）而直剪钢筋较少（小于0.60%）时，需要进行直剪承载力验算以保证设计安全。［关键词］直剪; 斜剪; 极限承载力; 试验研究; 设计方法中图分类号：TU375 文献标识码：A 文章编号：1002-848X(2014)19-0075-06Comparison on the ultimate bearing capacities of direct shear and oblique shear for RC members with pre-cracked sectionsLin Feng, Ou Zhixing, Lu Haixia(Department of Building Engineering, College of Civil Engineering, Tongji University, Shanghai 200092, China)Abstract: The ultimate bearing capacities (UBCs) of direct shear for reinforced concrete (RC) members can be remarkably reduced due to the presence of the cracks parallel to the shear force. The current design codes in China do not provide an appropriate approach to design or check the UBCs of direct shear, which may have hidden danger. To demonstrate this irrationality, experimental and analytical studies were conducted. Twenty-two Z-shaped specimens with different crack lengths, reinforcement ratios and direct reinforcement positions were tested to obtain their UBCs of direct shear. The results show that the UBCs decrease when the crack lengths increase, but the UBCs of direct shear are not affected by the reinforcement positions. Considering the approximately identical reliability with the method of analysis, the UBCs of oblique shear with various stirrup ratios were obtained with the same material and geometric features as the direct shear specimens. By comparing the UBCs of direct shear with those of oblique shear in two perspectives of the ultimate bearing capacity and the design value of bearing capacity, it is found that the failure of direct shear occurs prematurely in certain situations of throughout cracking, stirrup ratio more than 0.18% and longitudinal reinforcement ratio less than 0.60%.Keywords: direct shear; oblique shear; ultimate bearing capacity; experimental study; design method*同济大学土木工程学院光华基金课题。作者简介：林峰，博士，副教授，Email: lin_feng@tongji.edu.cn。参考文献［1］ROSST J. Direct shear failure in reinforced concrete beams under impulsive loading ［R］. Air Force Weapon Laboratory, Kirtland Air Force Base, 1983.［2］The joint ASCE-ACI Task Committee 426. The shear strength of reinforced concrete members ［J］. Journal of the Structural Division, 1973, 99(6):1091-1187.［3］BIRKELAND P W, BIRKELAND H W. Connections in precast concrete construction ［J］. Journal of the American Concrete Institute, 1966, 63(3): 345-368.［4］MATTOCK A H, HAWKINS N M. Shear transfer in reinforced concrete — recent research ［J］. PCI Journal, 1972, 17(2): 55-75.［5］WONG R C K, MA S K Y. Shear strength components of concrete under direct shearing ［J］. Cement and Concrete Research, 2007, 37(8): 1248-1256.［6］RAHAL K N. Shear-transfer strength of reinforced concrete ［J］. ACI Structural Journal, 2010, 107(4):419-426.［7］PETRO M D S, EDUARDO N B S J. A state-of-the-art review on shear-friction ［J］. Engineering Structures, 2012, 45(1): 435-448.［8］ACI 318R-05 Building code requirements for structural concrete (ACI 31805) and commentary ［S］. Earmington Hillsi American Concrete Institute, 2005.［9］AS 3600-2001 Australian standard for concrete structures ［S］. North Sydney:Standards Association of Australia,2001.［10］GB 50010—2010 混凝土结构设计规范［S］. 北京: 中国建筑工业出版社, 2011.［11］JGJ 1—91装配式大板居住建筑设计和施工规程［S］. 北京: 中国建筑工业出版社, 1992.［12］DG/TJ 08-2071—2010装配整体式混凝土住宅体系设计规程［S］. 上海：上海市城乡建设和交通委员会, 2010.［13］卢海霞. 静力荷载作用下钢筋混凝土构件的直剪性能研究［D］. 上海：同济大学，2013.［14］张申. 钢筋混凝土开裂面剪力传递性能研究［D］. 大连：大连理工大学， 2009.［15］MANSUR M A, VUNAYAGAM T, TAN K H. Shear transfer across a crack in reinforced high.strength concrete ［J］. Journal of Materials in Civil Engineering (ASCE), 2008, 20(4): 294-302.［16］MILLARD S G, JOHNSON R P. Shear transfer across cracks in reinforced concrete due to aggregate interlock and to dowel action ［J］. Magazine of Concrete Research, 1984, 36(126): 9-21.［17］WALRAVEN J C, FRENAY J, PRUIJSSERS A F. Influence of concrete strength and load history on the shear friction capacity of concrete members［J］. PCI Journal, 1987, 32(1):66-84.［18］MATTOCK A H. Shear transfer in lightweight reinforced concrete ［J］. PCI Journal, 1976, 21(1): 20-39.［19］WALRAVEN J C, STROBAND J. Shear friction in high-strength concrete ［C］//ACI International Conference on High Performance Concrete(SP-149). Singapore, 1994: 311-330.［20］HOFBECK J A, IRAHIM I O, MATTOCK A H. Shear transfer in reinforced concrete ［J］. Journal of the American Concrete Institute, 1969, 66(2): 119-128.［21］过镇海. 钢筋混凝土原理［M］. 北京：清华大学出版社，1999.［22］沈在康. 混凝土结构设计新规范应用讲评［M］. 北京：中国建筑工业出版社，1993.［23］MATTOCK A H, JOHAL L, CHOW H C. Shear transfer in reinforced concrete with moment or tension acting across the shear plane［J］. PCI Journal, 1975, 20(4):76-93.
