考虑剪跨比的新加梁与原混凝土#br# 界面承载力计算理论研究

基于课题组前期所做的新加梁与原混凝土界面承载力试验结果，分析新加梁与原混凝土界面承载力的主要影响因素，在不考虑界面粗糙程度的条件下，随着剪跨比λ的增大，截面正应力增大，界面承载力减小；达到极限承载力时，受拉纵筋均达到屈服。当λ≤2时，界面开裂，发生剪切破坏；当λ>2时，界面处较小受压区高度混凝土压碎，发生受弯破坏。基于新加梁端界面破坏机制及受力性能影响因素分析，提出考虑新加梁受拉纵筋抗力和剪跨比λ影响的新加梁与原混凝土界面承载力计算模型。由试验数据分析，建立反映剪跨比影响的新加梁与原混凝土界面承载力计算公式。通过大量已有试验结果对比分析，验证所提新加梁与原混凝土界面承载力计算公式的准确性和适用性。基于可靠性分析，建立满足可靠度要求的新加梁与原混凝土界面承载力计算公式。

Theoretical study on bearing capacity calculation of interface between newly#br# added beam and original concrete considering shear-span ratio

Based on the test results of the interface bearing capacity of the newly added beam and the original concrete made by the research group in the early stage, the main influencing factors of the interface bearing capacity of the newly added beam and the original concrete were analyzed. Without considering the roughness of the interface, with the increase of shear span ratio, the section normal stress increases, and the bearing capacity of the interface between the newly added beam and the original concrete decreases. The longitudinal bars can be yield when the load reaches to the ultimate bearing capacity. When λ≤2, the interface cracked and shear failure occurred. When λ>2, the concrete is crushed at a small height of the compression zone at the interface and bending failure occurred. Based on the analysis of the failure mechanism and the influencing factors of the mechanical performance for the newly added beam end interface, a calculation model of the bearing capacity of the newly added beam and the original concrete interface was proposed, which considered the influence of the resistance of the longitudinal reinforcement and the shear span ratio. Through the analysis of experimental data, the bearing capacity calculation formula of the interface between the newly added beam and the original concrete is established, which reflects the influence of shear span ratio. The accuracy and applicability of the proposed formula for calculating the bearing capacity of the interface between the newly added beam and the original concrete are verified through the comparative analysis of a large number of existing test results. Based on the reliability analysis, a formula for calculating the bearing capacity of the interface between the newly added beam and the original concrete is established, which can meet the reliability requirements.