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 f_t on the shear strength of deep flexural members, the relationship between the top node height l_c 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.