Experimental And Numerical Research Onbond Behavior Of Reinforcement Embedded InSelf-Compacting Lightweight Concrete Underlateral Tensile Stresses

Self-compacting lightweight concrete(SCLC)is a new type of concrete combined with the properties of self-compacting concrete(SCC)and lightweight aggregate concrete(LWAC),which has broad application prospects for structures such as high-rise buildings and long-span bridges due to its benefits in light weight,cost saving and faster construction.As a new building material,despite the fact that many efforts have been made to improve the material properties of SCLC,mainly in the optimization of mix proportion,durability,workability and mechanical behaviors,the researches on the bond behavior of SCLC are still not comprehensive.In real reinforced concrete structure,the bond behavior between reinforcing bar and concrete is mainly depend on the lateral confinement from surrounding concrete,and the stress states of surrounding concrete will exert significant influences on the lateral confinement.In order to ensure the application of SCLC in engineering practice,this thesis studied the bond behavior of steel bars embedded in SCLC subjected to lateral tensions by means of experiment and numerical simulation.The main contents and conclusions are as follows:(1)The bond-slip response of plain round bars embedded in SCLC under lateral tension was studied through pull-out tests.The parameters of the compressive strength,ratio of concrete cover depth to bar diameter and combinations of lateral tensions on the bond property were coonsidered and the calculation models for main bond parameters were given.The experimental results on 46 series of pull-out specimens showed that,when the lateral tensions are applied,pullout failure happens to all specimens for different strengths of SCLC and bar diameters.As the average lateral tension increases,the bond strengths decrease linearly.For the pull-out tests under uniaxial lateral tension,the slip increases with the uniaxial lateral tension increases,while for the pull-out tests under biaxial lateral tension,the slip firstly increases with the increased biaxial lateral tension and then exhibits a stable tendency.(2)The bond behavior of deformed bars embedded in SCLC under lateral tensions was studied and calculation models for bond parameters were provided.The experimental results on 60 series of pull-out specimens showed that,with the lateral tension increases,both of the bond strength and the slip at the peak decreases.For the specimens with the same strength of concrete and ratio of the cover depth to bar diameter(i.e.,c/D),the splitting failure occurs more possibly as the lateral tension increases.For the specimens in pull-out failure,the ratio of the residual to ultimate bond strength almost keeps invariable.(3)Based on the experimental data,an empirical local bond stress-slip relationship for steel bars was proposed.When the diameter of the bar,the depth of cover,the strength of concrete,and the magnitude of lateral stresses are given,the bond stress-slip curve between the steel bar and concrete can be determined.The proposed formula is in good agreement with the experimental results.(4)A 3D nolinear finite element approach has been presented by ABAQUS software to predict the bond property between SCLC and deformed bars.The effect of expansion angle,yield surface shape parameters and viscosity coefficient on the bond-slip relationship was investigated for the specimens without lateral tension.The bond stress-slip relationship between SCLC and deformed bars under different lateral tensions were analyzed by finite element analysis and verified against the experimental results.The numerical calculation results agree well with the experimental results.