无腹筋RC悬臂梁抗剪强度及尺寸效应理论研究

不同于混凝土材料,钢筋混凝土(RC)构件的破坏模式与机制更为复杂,采用混凝土材料尺寸效应理论难以描述构件的尺寸效应行为。我国相关规范中并没有系统考虑构件尺寸及纵筋率对RC梁抗剪承载力的影响。为研究剪跨比及纵筋率对无腹筋RC梁剪切破坏及抗剪强度尺寸效应的影响,采用三维细观数值模拟方法,建立了RC梁剪切破坏力学分析模型,研究了剪跨比及纵筋率对RC梁剪切破坏及抗剪强度尺寸效应的影响机制与规律。研究结果表明,RC梁抗剪强度表现出极为显著的尺寸效应现象;RC梁抗剪强度随剪跨比的增大而减小,随纵筋率的增大而增大;剪跨比较小时,纵筋率对抗剪强度的影响尤为显著。此外,基于Ba■ant材料层次尺寸效应律,提出了考虑剪跨比及纵筋率影响的RC梁抗剪强度尺寸效应理论公式。对比试验结果,验证了所提公式的准确性与合理性。

Size effect theory on shear strength of RC cantilever beams without stirrups

Different from concrete materials,the failure modes and mechanisms of reinforced concrete (RC) members are very complex.It is difficult to describe the size effect of RC members by using the size effect theory of concrete materials.There is no systematic consideration of the influence of member size and longitudinal reinforcement ratio on shear capacity of RC beams in relevant codes of China.In order to study the effects of shear-span ratio and longitudinal reinforcement ratio on the shear failure and size effect of shear strength of RC beams without stirrups,a mechanical analysis model for shear failure of RC beams was established by using 3D meso-scale numerical simulation method,and the mechanism and regularity of the effects of shear-span ratio and longitudinal reinforcement ratio on the shear failure and size effect of shear strength of RC beams were studied.The results showed that the shear strength of RC beams exhibits a significant size effect:it decreases with the increase of shear-span ratio and increases with the increase of longitudinal reinforcement ratio;the effect of longitudinal reinforcement ratio on shear strength is particularly significant when the shear-span ratio is small.In addition,based on the Bažant''s Size Effect Law (SEL) for materials,a theoretical formula for the size effect of shear strength of RC beams considering the effects of shear-span ratio and longitudinal reinforcement ratio is proposed.The accuracy and rationality of the proposed formula are verified by comparison the experimental results.