Experimental Study On Compressive Behavior Of Concrete Columns Strengthened With HDC And RPC

High Ductile Concrete,hereafter this text will be abbreviated as HDC,is a kind of cement-based composite material with high strength and toughness.Compression shows good compressive toughness,tension strain hardening characteristics,which can significantly improve the seismic performance of masonry members,improve the bearing capacity and ductility of concrete members.Reactive Powder Concrete,hereafter this text will be abbreviated as RPC,has the characteristics of super high strength,low brittleness and high impermeability.It can improve the shear and flexural properties of reinforced concrete columns and beams,and improve the brittle failure of specimens.In this paper,the axial compressive and eccentric compressive properties of HDC and RPC strengthened columns are studied by experiment and numerical simulation.The effects of different strengthening materials and methods on the strengthening effect are considered.The working mechanism of the interface between the strengthened layer and concrete is analyzed.The calculation methods of compressive bearing capacity of the axial and eccentric compressive members of HDC and RPC strengthened columns are given.(1)Experimental study on axial compression behavior of reinforced columns.Based on the axial compression tests of seven reinforced specimens and one unreinforced specimens,the effects of reinforcement material,compression mode and reinforcement network on the test results are studied.The failure modes,load-displacement curves and strain development laws of the specimens are analyzed.The test results show that the failure modes of each reinforced column are improved,the damage resistance of HDC reinforced layer is better than that of RPC reinforced layer,the integrity of reinforced layer with steel mesh is stronger,the interface between each reinforced layer and concrete has reliable bond strength and deformation coordination,and the mechanical properties of directly compressed reinforced layer are fully developed,and the bearing capacity of corresponding reinforced specimens is greatly improved.(2)Experimental study on eccentric compression behavior of reinforced columns.Through eccentric compression tests on 6 reinforced specimens and 2 unreinforced comparative specimens,the effects of eccentricity,reinforcement material and reinforcement layer with steel mesh on the test results are studied,and the failure modes,load-displacement curves and strain development laws of the specimens are analyzed.The test results show that the failure modes of eccentrically loaded columns are improved,and the stiffness,bearing capacity and deformation capacity of eccentrically loaded specimens are improved by the reinforcement layer.(3)Finite element analysis of mechanical behavior of reinforced compressive members.In this paper,ABAQUS finite element software is used to model and analyze the axial compression and eccentric compression tests of reinforced columns.The failure modes,load-displacement curves and strain development laws of each finite element model are compared and analyzed.The results show that the finite element model can well simulate the axial compression test of reinforced columns.The bearing capacity,load-displacement curve,stress distribution of components and crack development in the simulation results are in good agreement with the test results.By comparing the simulation results with the experimental results of eccentric compression test,the reliability of the finite element model is proved.The numerical simulation expands the experimental results and provides a basis for the later calculation of bearing capacity.(4)Calculation of bearing capacity of normal section of reinforced columns under axial and eccentric compression.By analyzing the working mechanism of the reinforced layer,the influence of the shear force between the reinforced layer and the concrete under different loading conditions on the strengthening effect is studied.The utilization coefficient and shear transfer coefficient of the reinforced layer are given.The calculation method of the compressive bearing capacity of the normal section of the reinforced column under axial compression is obtained,and the calculation results of the bearing capacity are in good agreement with the experimental results and the simulation results.On the basis of the research,the utilization coefficient of the reinforced layer of eccentrically compressed columns is given,and the calculation method of the compressive bearing capacity of the normal section of reinforced eccentrically compressed columns is obtained by simplifying the calculation with the equivalent rectangular stress figure coefficient.By comparing the calculation results with the simulation results and the test results,it can be seen that the calculation method has high accuracy and reliability.