| At present,the development of South China Sea,the maritime Silk Road and the construction of Guangxi Beibu Gulf sea passage for ASEAN countries are the hot spots of China’s economic development.A large number of municipal infrastructure of concrete structures need to be built,but the steel bars in the concrete structures are vulnerable to chloride corrosion in the coastal and marine areas,resulting in serious decline in the durability of the structures.This problem can be solved by using the excellent corrosion resistance of BFRP bars.If the BFRP reinforcement is combined with seawater and sea sand concrete,the fundamental problem of the extreme shortage of river sand and fresh water resources for concrete pouring in the above areas can also be effectively solved.In this paper,BFRP longitudinal bars reinforced seawater and sea sand concrete compression column as the research object,through the static loading test and theoretical analysis of eccentrically compressed short column specimens,the compression performance of such members is studied.In this paper,15 tensile specimens and 36 compression specimens of BFRP bars are made.The tensile properties of three different diameters of BFRP bars and the compression properties of three different diameters and slenderness ratios of BFRP bars are studied by monotonic static loading test.The seawaterand sea sand concrete mix ratio of target strength was obtained by nine groups of mix ratio experiments.Eleven short columns reinforced with BFRP longitudinal bars were designed.The eccentricity,reinforcement ratio and concrete strength were taken as design parameters to study the influence of the columns on crack development,characteristic load,deflection and failure mode.Based on the above test data,the calculation formula of the bearing capacity of the concrete short columns strengthened by longitudinal reinforcement is derived.Through the above research,the following conclusions are drawn:(1)the tensile failure mode of BFRP bars is divided into tensile failure and local tensile failure,which belongs to brittle failure.The stress-strain relationship is linear elasticity.The tensile strength decreases with the increase of BFRP bar diameter,and the depth of thread concave rib will have a certain impact on the tensile strength.(2)the failure modes of BFRP bars are divided into shear failure,splitting failure,buckling failure and composite failure,which belong to brittle failure;the compressive strength of BFRP bars is only about 1/3 of the tensile strength,and the compressive modulus of elasticity of BFRP bars is about 2/3 of the tensile modulus;the compressive stress-strain curve of BFRP bars is basically linear.(3)When the other parameters are the same,the larger the eccentricity is,the smaller the concrete cracking load and ultimate load are,the larger the concrete lateral deformation and ultimate tensile and compressive strain are,andthe larger the strain of BFRP longitudinal reinforcement on both sides of the column is.When other parameters are the same,the larger the reinforcement ratio is,the greater the tensile strain of concrete is,and the stronger the lateral deformation resistance ability is,but the influence on cracking load and ultimate load,compression side edge compressive strain of concrete and longitudinal strain of BFRP on both sides is not significant;when other parameters are the same,with the increase of concrete strength grade,the lateral deformation resistance ability of column is enhanced,and for the partial pressure with tensile area.For short columns,the slope of load concrete tensile strain curve increases,and the tensile and compressive strains of BFRP longitudinal bars on both sides decrease.(4)The ratio of the theoretical value to the measured value is between 0.83 and 1.14,which can be used to predict the eccentrically compression bearing capacity of the short seawater and sea sand concrete columns strengthened by BFRP longitudinal reinforcement. |
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