Study On Large Eccentric Compression Performance Of Steel-FRP Composite Reinforced Concrete Columns Under Marine Service Environment

The results show that the Steel-FRP composite bars have good durability in corrosive marine environment.After the yield of the inner core steel bar,the longitudinal continuous fiber begins to play a role.The specimens show similar stable secondary stiffness and good ductility as ordinary steel bars,and the failure point of the component is the tensile fracture of the longitudinal continuous fiber.In order to study the compression performance of concrete columns in marine service environment,the eccentrically compressed concrete columns with steel FRP composite bars were designed and fabricated under the coupling action of chloride corrosion and load erosion.The effects of reinforcement ratio and As/Af on the ultimate bearing capacity,deflection,crack width and failure mode of eccentrically compressed concrete columns were studied It provides a basis for the future research on the durability of steel FRP composite reinforced concrete members.The main contents of this paper are as follows.(1)The tensile and compressive properties of steel FRP composite bars under the coupling action of Chloride Erosion and load chloride corrosion were tested.The yield strength and ultimate strength of steel bars under different erosion time and different load levels were measured,and the tensile and compression constitutive models of steel bars were given.(2)The concrete columns with Steel-FRP composite bars corroded by chloride salt were tested under eccentric compression.The variation of concrete compressive strain,member deflection and crack width with the increase of load were measured.The analysis of the test results shows that the test column conforms to the assumption of plane section,and the compressive strain of concrete increases gradually with the extension of erosion time.The ultimate bearing capacity of concrete column first increases and then decreases with the increase of erosion time.When the reinforcement ratio increases from 2.09%to 3.14%,the ultimate bearing capacity of the specimen increases by 20%.When As/Af increases from 33.3%to 78.8%,the ultimate bearing capacity of the member increases by 7.5%.(3)Eccentrically loaded concrete columns with Steel-FRP composite bars subjected to chloride corrosion are tested.The variation of concrete compressive strain,member deflection and crack width with the increase of load are measured under different corrosion time and load level.The analysis of the test results shows that the test column conforms to the assumption of plane section.The larger the load level is,the larger the slope of the load deflection curve is,and the smaller the secondary stiffness of the component is.The larger the reinforcement ratio is,the greater the stiffness of reinforcement is,and the smaller the maximum midspan deflection is.The ultimate bearing capacity of concrete column decreases with the increase of load level.When As/Af increases from 33.3%to 78.8%,the ultimate bearing capacity increases.With the increase of load level,the maximum crack width increases.(4)Based on the constitutive model of concrete and Steel-FRP composite bars,the formulas of moment amplification factor,failure mode,bearing capacity and crack width are established.The theoretical prediction is in good agreement with the experimental results,which shows that the established formula is effective.