Flexural Behavior Of High-strength Lightweight Aggregate Concrete Beams Reinforced With High-strength Steel Bars

The combination of high-strength reinforcement and high-strength light-aggregate concrete can give full play to the performance advantages of both and reduce the cross-sectional size and the amount of reinforcement of the members.In this paper,the bonding performance of HRB600 grade high-strength reinforcement and high-strength light-aggregate concrete and the flexural performance of beams are studied,and the calculation models of ultimate bearing capacity,deflection and crack width of these beam members are established,which provide theoretical guidance to promote the application of high-strength reinforcement and highstrength light-aggregate concrete.The main research contents are as follows:(1)13 sets of central pull-out tests were completed to analyze the influence of key factors on the bond performance between high-strength reinforcement and high-strength lightaggregate concrete,the ultimate bond strength and residual bond stress between them both increase with the increase of concrete strength;the increase of anchorage length decreases the average bond strength;the bridging action of steel fibers can improve the tensile strength of high-strength light-aggregate concrete,so that the bond-slip The decreasing section of the bondslip curve tends to be flat;increasing the protective layer thickness can effectively improve the restraining effect on the reinforcement,and the concrete protective layer thickness has less influence on the bond strength when c/d is greater than 3.75.(2)The bond strength of high strength lightweight aggregate concrete is theoretically determined by taking into account the material properties of high strength lightweight aggregate concrete and the softening behavior of concrete in the cracking zone,which is based on the thick walled cylinder model.Finally,a theoretical calculation approach for bond strength is attained,which carefully takes into account the concrete’s cracked and uncracked zones;For high-strength steel bars and high strength lightweight aggregate concrete,a three-stage bond slip constitutive relationship model is presented based on the characteristics of the experimental bond stress-strain curve and the bond strength calculation model.The model’s anticipated outcomes are reasonably close to those of the experiment.(3)Completed bending performance tests on 5 HRB600 grade high-strength reinforced high strength lightweight aggregate concrete beams,clarifying how different factors affect the failure process,the bending moment mid span deflection curve,ultimate bearing capacity,crack propagation,concrete and steel strain,and the behavior of this type of beam under different conditions.The results show that all components have undergone reinforcement failure,the tensile steel bars yield,and the top concrete is crushed;The addition of steel fibers slows down the generation and expansion of cracks,significantly improving the ductility of components;The bending stiffness and bearing capacity of the beam increase with the increase of reinforcement ratio;An increase in the clear span length will reduce the flexural bearing capacity of the component and the ductility coefficient;The ultimate bearing capacity of such components is slightly increased and their ductility is slightly decreased due to the rise in concrete strength.(4)We conducted an analysis of the bending bearing capacity and deformation performance of high-strength reinforced high strength lightweight aggregate concrete beams.Based on the calculation methods provided by the specifications,combined with the influence of material characteristics and characteristic factors on the bending performance of beams,we developed a mathematical model for the crack width,mid span deflection,and bending bearing capacity of high strength lightweight aggregate concrete beams appropriate for high-strength steel bar configuration.The findings show that the proposed model’s projected results and experimental findings are in good agreement,and that the model can be utilized to calculate the bending performance indicators of high strength lightweight aggregate concrete beams and high-strength steel bars.The bonding performance and beam bending performance of HRB600 high-strength steel bars and high strength lightweight aggregate concrete are investigated experimentally and theoretically in this work,proposes a bond strength calculation model and a bond slip constitutive relationship model,and establishes a calculation model for the ultimate bearing capacity,mid span deflection,and crack width of this type of beam component.This has theoretical guidance significance for promoting the engineering application of high-strength steel bars and high strength lightweight aggregate concrete.