Study On Shear Property Of New And Old Concrete Bonding Surface

The new and old concrete bonding problem is a key concern in the reinforcement and repair of concrete structures,and the bonding strength will directly affect the reliability and durability of the reinforced structure.The studies on the new and old concrete interface treatment methods and the connection methods show that setting steel bar connectors on the interface between new and old concrete can improve the bonding strength efficiently.But the current research on the new and old concrete reinforcement treatment is mostly limited to the bonding performance of single rebar,but the actual situation is a complicated state of stress under the action of a plurality of steel bars.In this thesis,the bonding performance of multiple reinforcing bars was studied by experiments and finite elements analysis.The main work is as follows:1.Experimental studies: With the consideration of the influence of the steel bar diameter and the arrangement of steel bars on the bonding performance of the interface,this paper conducted a shear experiment on 8 different groups of 16 Z-shape specimens.Comparing the failure patterns and mechanical mechanisms of specimens during integral concreting,with and without planting bars,and under the condition of different reinforcement ratio on the shear bearing capacity of specimens are discussed,studying the mechanical property of reinforced steel bar under different arrangement.The analysis of the test load and reinforcement strain confirmed the implantation of shear reinforcement on the bearing capacity of specimens increased,and verified the triangular arrangement has a higher bearing capacity.2.Finite element analysis: The contact unit of new and old concrete was established,considering the factors of steel bar diameters,elasticity modulus,planting pattern and other factors,and deeply analyzed the bearing capacity and bonding strength of new and old concrete specimens are analyzed.The study shows that the concrete elastic modulus ratio has little influence on the ultimate shear stress of the new and old concrete,and the appropriate increase of the diameter of the reinforcement can effectively improve the shear strength of the concrete.3.The innovation of this paper: Research triangle and square two different arrangements influence the shear strength of new and old concrete.the new and old concrete model was improved to analyze the effect of different elasticity modulus and steel bar diameters to new and old concrete interface stress and displacement.