Study On Shear Performance Of UHPC-NC Prestressed Composite Beams Without Web Reinforcement

Compared with ordinary concrete,the ultra-high performance concrete(UHPC)material based on the maximum bulk density theory has the characteristics of high compressive and tensile strength,good fracture toughness and strong durability.UHPC-NC prestressed composite beam without web reinforcement gives full play to the mechanical properties of UHPC material,and is a new type of bridge structure with excellent cost performance.However,there is no unified calculation formula for shear capacity of UHPC-NC prestressed composite beam without web reinforcement.,and the theoretical value obtained by the existing structural shear bearing capacity calculation formula has a large deviation from the experimental value,and the existing traditional reinforced concrete shearing theory has not been able to explain the experimental phenomenon very well.Theoretical research and experimental analysis are carried out on NC prestressed composite beams without web reinforcement.The main research work carried out in this paper includes:(1)The material properties of UHPC,the characteristics of UHPC-NC prestressed composite beams without web reinforcement and the existing shear calculation theory of reinforced concrete beams are reviewed.(2)Using the structural design parameters of the real bridge,15 full-scale UHPC-NC prestressed composite beams without web reinforcement were subjected to shear bearing capacity failure tests.The effects of key parameters such as shear-span ratio,steel fiber content,web thickness and compressive stress level on the deflection of the test beam,the relative slip of the interface between different materials,the change of structural stiffness,and the occurrence and development of cracks are studied.(3)The shear ductility of UHPC-NC prestressed composite beams without web reinforcement is discussed.According to the test data,the relationship between the main strain direction of the web,the bending deformation and the total deformation of the structure,and the changing law of the static and dynamic stiffness of the structure are analyzed.(4)The stress process of the test beam is simulated based on the finite element simulation analysis software,and the key parameters are further analyzed more comprehensively.According to the test results and finite element analysis,the test values of 15 full-size UHPCNC prestressed composite beams without web reinforcement were fitted,and the calculation formula of shear bearing capacity of UHPC-NC prestressed composite beams without web reinforcement was proposed.