考虑尺寸效应的深受弯构件受剪模型分析

深受弯构件斜截面受剪机理复杂且受尺寸效应影响显著，缺乏准确、合理的受剪计算模型。结合Tan-Cheng模型中对混凝土软化作用和深受弯构件尺寸效应的全面考虑优势，在深入研究混凝土斜压杆倾角α和构件复合抗拉强度f_t对深受弯构件受剪承载力影响的基础上，简化压杆顶部节点区高度l_c与α的关系，考虑腹筋有效作用区域修正复合抗拉强度f_t计算模型，提出了不影响精度前提下的修正Tan-Cheng模型。研究表明:基于国内外308组深受弯构件受剪试验数据计算结果，建议模型计算精度等同Tan-Cheng模型，并能够准确考虑尺寸效应影响，但计算过程较为简洁；通过与现有典型各国规范建议模型对比分析表明，计算结果较规范计算值更接近试验值，能够更准确地对深受弯构件的受剪承载力进行预测。

A SHEAR DESIGN MODEL FOR RC DEEP FLEXURAL MEMBERS CONSIDERING THE SIZE EFFECT

There is a lack of accurate and reasonable shear design models for reinforced concrete deep flexural members such as typical D-region shear components with complicated force mechanism and significant size effect. In combination with the advantages of the Tan-Cheng model that fully considers the softening effect of concrete and the size effect of struts, and on the basis of the deep understanding of the effect of diagonal strut angle α and composite tensile stress ft on the shear strength of deep flexural members, the relationship between the top node height lc and α was simplified and a modified Tan-Cheng model was proposed by reconsidering the effective action region of web reinforcement. The predictions of 308 deep flexural members from either foreign or domestic source indicate that the proposed model has a comparable accuracy with the Tan-Cheng model, and it can accurately consider the size effect of concrete struts through a concise calculation process. The comparison between the proposed model and current code provisions shows that the predictions by the proposed model has a better agreement with the test results. It further indicates that the proposed model can reasonably predict the shear strength of deep flexural members.