Analysis On The Shear Behavior Of High-strength Concrete Beams With High-strength Stirrups

The shear failure mechanism of reinforced concrete beams is so complicated that it has been an important research direction in reinforced concrete structure for a long time. At present, the shear research of ordinary reinforced concrete beams is relatively mature, while the shear research of high-strength concrete beams with high-strength stirrups is relatively few. In the current concrete structure design code, the shear formula of reinforced concrete beams is deducted based on the test data of ordinary reinforced concrete beams. The research shows that the shear formula on the code is too safe when it is used on high-strength concrete beams with high-strength stirrups. In this paper, six high-strength concrete beams with high-strength stirrups are designed to analyze the shear performance.1. The shear performance tests of high-strength concrete beams with high-strength stirrups are designed in this paper. The diagonal cracking characteristics, the diagonal crack development, the crack failure pattern, the beam shear ductility and the ultimate bearing capacity factors of high-strength concrete beams with high-strength stirrups are analyzed under the concentrated load. This paper focus on the analysis of shear-span ratio, the stirrup ratio and the concrete strength which can affect the crack development and the ultimate bearing capacity of the test beams.2. Based on the Classical Modified Compression Field Theory, an improved Modified Compression Field Theory is put forward in this paper. On the basis of Classical Modified Compression Field Theory, at the same time, considering the shear effect of concrete in compression zone, ignoring the foxtail effect of longitudinal reinforcement, but considering the impact of longitudinal reinforcement to the height of concrete in compression zone, the improved Modified Compression Field theory is put forward. Meanwhile, The shear formula of high-strength concrete beams with high-strength stirrups is given. The parameters of α1 and β and θ in formula are simplified. and the practical simplified formula is given, and it is verified by some relevant test data about high-strength concrete beams with high-strength stirrups.3. The diagonal crack influencing factors and the maximum crack width ofhigh-strength concrete beams with high-strength stirrups are researched in this paper.The relationship between variables is analyzed according to the curve between stirrups average stress and maximum crack width. The shear force under normal use stage is analyzed in accordance with the affecting factors of ultimate shear capacity in current code, and the formula of maximum crack width is put forward.4. The modeling analysis of finite element analysis model about high-strength concrete beams with high-strength stirrups which is established based on ABAQUS is analyzed. Firstly, the finite element model is verified by contrasting with the test results. Secondly, the effect to the ultimate shear capacity of relevant parameters in the high-strength concrete beams with high-strength stirrups is researched by changing the model parameters such as stirrups strength and shear span ratio.