Study On The Compression Behavior Of Concrete Column Reinforced With Steel-FRP Composite Bar(SFCB)

Reinforced concrete structures are most widely used in the field of construction engineering.However,reinforced concrete structures in harsh envirorunents are often broken prematurely mainly due to the corrosion of steel bars inside the structure.Concrete structure reinforced with FRP can better solve this problem.However,the concrete structure reinforced with FRP has poor ductility,large deflection and crack,which is characterized by brittle failure.Steel-FRP Composite Bar(SFCB)is a new fiber reinforced composite material,the inner core of which is ordinary steel bar and wrapped by fiber.It has high strength,good ductility,stable secondary stiffness,excellent corrosion resistance and other advantages.Applying SFCB to strengthen concrete structures can well solve the problem of insufficient durability in reinforced concrete structures.In this paper,SFCB was used to replace the ordinary steel bar forming concrete column reinforced with SFCB,and it was subjected to static compression test.And it was tested under pressure.Based on the theoretical analysis and ABAQUS software simulation,we studied the influence of eccentricity,slenderness ratio,types of reinforcement(SFCB/steel bar/FRP reinforcement/FRP reinforcement and mixed reintorcement),reinforcement ratio and the ratio of the inner steel bar area and outer fiber area in terms of the ultimate bearing capacity,crack,deflection and failure mode of the SFCB concrete column.The main research results of the thesis are as follows:(1)The tensile and compressive tests of SFCB showed that the mechanical properties of SFCB under compression were quite different from those under tension.SFCB in tension and compression zone cound not be regarded as equal.The constitutive model of SFCB material under tension and compression was presented for component analysis and calculation.(2)Under axial load,the ultimate bearing capacity of SFCB concrete column was larger than that of reinforced concrete column,which was smaller than that of concrete column reinforced with BFRP.(3)Under the eccentric load,the deflection of reinforced concrete column was the smallest and the deflection of BFRP reinforced concrete column was the largest.The deflection of SFCB concrete column was between them.Under the same reinforcement ratio.the deflection of SFCB concrete column was smaller than that of mixed reinforced concrete column.The crack width of reinforced concrete column was the smallest and the crack width of BFRP reinforced concrete column was the largest.The crack width of SFCB concrete column was between them.Under the same reinforcement ratio,the crack width of SFCB concrete column was greater than that of mixed reinforced concrete column.The ultimate bearing capacity of SFCB concrete column was the largest,which was close to that of concrete column reinforced with BFRP.Under the same reinforcement ratio,the ultimate bearing capacity of SFCB concrete column was smaller than that of mixed reinforced concrete column.(4)The influence of eccentricity,reinforcement ratio and slenderness ratio on compressive performance of SFCB concrete columns was the same as that of reinforced concrete columns.The larger the eccentricity was,the larger the lateral deformation was.The larger the maximum crack width was,the smaller the ultimate bearing capacity was.The larger the reinforcement ratio was,the smaller the lateral deformation was.The larger the ultimate bearing capacity was,the smaller the maximum crack width was.The larger the slenderness ratio was,the larger the lateral deformation was.(5)The larger the ratio of As/Af was,the greater the stiffness of SFCB concrete column was.The larger the ratio of As/Af was,the smaller the lateral deformation was.The ratio of As/Af haved no obvious influence on the ultimate bearing capacity and crack width of SFCB concrete columns.The ratio of As/Af cound be adjusted to meet the design requirements in practical use.(6)In this experiments the maximum deflection and ultimate bearing capacity of SFCB concrete columns with longitudinal bars enclosed by BFRP were similar to those of SFCB concrete columns with longitudinal bars enclosed by GFRP.The crack width of SFCB concrete column with longitudinal reinforcement wrapped with BFRP was larger than that of SFCB concrete column with longitudinal reinforcement wrapped with GFRP.(7)Based on the constitutive models of concrete and SFCB,we derived the formula of the normal section bearing capacity of SFCB concrete column.The calculated values were smaller than the measured values,which were safe.We derived the eccentricity increasing coefficient.When calculating the eccentricity increasing coefficient by using the standard formula,the correction coefficient ot section curvature oi members with different kinds of reinforcement must be introduced.The Nu-Mu related equation of the derivative was safer than the actual value.(8)The yield load,the longitudinal stress state and the concrete axial stress were close to the test,when we simulated the SFCB concrete column under eccentric load by ABAQUS software.The SFCB concrete columns with three concrete strengths were simulated and we found that the greater the concrete strength was,the higher the bearing capacity and the greater the deflection was.SFCB concrete columns with longitudinal bars enclosed by CFRP was added to be simulated and we found the bearing capacity of SFCB concrete columns with longitudinal bars enclosed by CFRP was greater than that of SFCB concrete columns with longitudinal bars enclosed by BFRP or GFRP because strength and modulus of elasticity of SFCB outsourcing CFRP was larger than that of SFCB outsourcing BFRP or GFRP.It was found that the higher the strength grade of inner core steel bar was,the stronger the resistance to deformation and the greater the ultimate bearing capacity of SFCB concrete column were,when adding the simulation of S8B30 concrete columns with three grades of inner steel bars...