Shear Strength Study For Reinforced Concrete Beams With Web Reinforcements Against Size Effect

The shear theory of reinforced concrete beam has more than 100 years,For the shearfailure mechanism of reinforced concrete beams is complicated,the shear strength theory is not uniform in the design specifications of each country,it is still a hot topic for domestic and foreign scholars.The design code for shear strength of reinforced concrete beams in different countries are mostly based on the analysis of the small-size beam test data to obtain empirical or semi-empirical formula,so it’s difficult to guarantee the accuracy of large-size beams in industrial,civil buildings,special structures and so on.Based on that,on the basis of a large number of domestic and foreign literature,established the shear strength test database of reinforced concrete beams with web reinforcement.The theoretical analysis and numerical analysis of shear strength of reinforced concrete beams with web reinforcement are studied,The relevant conclusions are summarized as follows(1)Through a large number of domestic and foreign literature review,a test database containing 627 shear tests for reinforced concrete beams with web reinforcement was established.The database of the concrete strength is transformed into the compressive strength of the cylinder’s compressive strength,units unified for the millimeter,kernels,MPa and so on.The compressive strength of the concrete cylinder in the database is fc ’=12.8~125.4MPa,the effective height of the section is d=21~1500mm,a span ratio of a/d=0.27~7.2,longitudinal reinforcement rate range ρ=0.49%~6.97%。(2)Based on the database,the influence of concrete strength,longitudinal reinforcement ratio,shear span ratio and stirrup ratio on the shear strength of reinforced concrete beams was analyzed,and the shear strength of reinforced concrete beams increases with the increase of concrete strength,longitudinal reinforcement ratio and stirrup rate,and decreases with the increase of shear span ratio.(3)According to the Modified Compression-Field Theory and the Ba?ant’s scale law,the shear strength formula of the reinforced concrete beam with the size effect is obtained.The theoretical formula,GB Concrete standards(GB50010-2010),ACI Concrete standards(ACI318-14)and CSA Concrete standards(CSA A23.3-2014)in the formula of shear strength were compared with experimental data collected,The shear strength formula obtained in this paper agrees well with the experimental data.(4)Ensuring that the concrete strength,longitudinal reinforcement rate,stirrup ratio,shear span ratio and other factors unchanged,through the ANSYS established four reinforced concrete beam model,to study the effective height of the impact on the shear strength.The results show that there in no size of cracking strength during the shear process,while the ultimate strength has a significant size effect.Compared with the beam with a cross section height of 300 mm,the shear strength of beam with a cross section height of 600 mm,900mm and 1200 mm has decreased by 6 %,10%,20% respectively.It can be seen that the shearing strength of the model beam decreases with the increasing beam height,and the decreasing trend gradually increases.