BFRP Stirrup Confinement Of Coral Concrete Column Axial Pressure Performance

The use of coral debris instead of sand and gravel aggregate to prepare coral concrete can effectively alleviate the shortage of construction materials for ocean-going islands and reefs and promote the development process of marine construction in China.Under the dual influence of the marine environment and the high chloride content of coral debris,ordinary steel bars cannot resist the erosion of harsh environments,and the use of fiber reinforced plastic bars with high corrosion resistance(FRP)can effectively solve such problems.Since FRP reinforcement is a linear elastic material,and the brittle characteristics of coral concrete are more obvious than ordinary concrete,the axial compressive performance of FRP rib-constrained coral concrete column is different from that of ordinary reinforced concrete column,in order to explore the axial compression performance of BFRP stirrup constrained coral concrete column,the following studies are mainly carried out:1.The mechanical properties of BFRP ribs and coral concrete used in the components were tested,and the results showed that the tensile performance of BFRP ribs was related to the diameter of the reinforcement,and the smaller the diameter,the better the tensile performance;Its compressive performance is much lower than that of tensile performance,and the compressive elastic modulus is close to the tensile elastic modulus.Affected by the production process,the larger the diameter of the BFRP stirrup,the smaller the tensile strength reduction coefficient;When the coral concrete is crushed,there is no obvious warning,showing obvious brittle failure characteristics.2.On the basis of the study of the mechanical properties of coral concrete and BFRP reinforcement,the axial pressure performance test of 10 BFRP stirrup constrained coral concrete columns was carried out,mainly considering the influence of stirrup form,stirrup spacing,stirrup diameter and coral concrete strength,and obtained the force process and failure form of BFRP stirrup constrained coral concrete column,and the influence of the above factors on the bearing capacity and deformation capacity of BFRP stirrup constrained coral concrete column was analyzed.The results showed that the stress process of BFRP stirrups constraining coral concrete columns was divided into elastic stage,elastoplastic stage and post-peak stage.When the test column fails,the crack morphology is roughly divided into three types,namely "H" shaped crack,"N" shaped crack and oblique crack.The stirrup constraint has little effect on the bearing capacity of the test column,the larger stirrup diameter and smaller stirrup spacing can improve the ductility of the column,the constraint effect of the composite stirrup is better than that of the ordinary square stirrup,and with the increase of the strength of coral concrete,the restraining effect of the stirrup is reduced.3.Referring to the existing restraint mechanism of steel stirrups on concrete columns,combined with the concepts of effective constraint area and effective lateral constraint stress,the peak stress and peak strain calculation model of BFRP stirrup constrained coral concrete column are proposed.The results of this test show that the existing calculation formula for the bearing capacity of fiber-reinforced concrete structures can meet the calculation of the bearing capacity of BFRP stirrup constrained coral concrete columns.4.Based on the existing constitutive model of stirrup constrained concrete,combined with experimental data,a stress-strain curve model suitable for BFRP stirrup constrained coral concrete is proposed,which provides a reference for the future promotion of BFRP coral concrete structure.