Finite Element Analysis On Mechanical Behaviors Of Sea Sand And Seawater Concrete Eccentric Compression Moderate Long Columns With BFRP Bars

In the construction of offshore areas,a large amount of river sand and water need to be used,which not only consumes time and cost,but also causes serious damage to the ecological environment caused by over exploitation of river sand.The gradation of grain of sea sand is similar to that of river sand,so it is suitable to replace river sand as fine aggregate of concrete.Sea sand is rich in chloride ion,which can easily lead to accelerated corrosion of steel bars in concrete structures,and if the concrete is mixed with unprocessed sea water,it will be disadvantageous to the concrete structure.Fiber reinforced polyme have excellent resistance to the corrosion of acids and bases,FRP bar instead of steel bar used in sea sand and seawater concrete structure is an effective method to preventing steel corrosion.In this paper,the ABAQUS finite element software is used to simulate the sea sand and seawater concrete eccentric compression moderate long columns with BFRP bars,and the influencing factors of eccentric compression mechanical properties and bearing capacity are analyzed.And the calculation method of bearing capacity of sea sand and seawater concrete eccentric compression moderate long columns with BFRP bars was given.The main contents and results are as follows:1.Verified that the feasibility of the finite element model of the BFRP bars reinforced sea sand and seawater concrete eccentric compression short columns.On the basis of the experiment obtained from the eccentric pressure of the BFRP bars reinforced sea sand and seawater concrete short columns which completed by our research group,three finite element models of the BFRP bars reinforced sea sand and seawater concrete eccentric compression short columns were established.And compared simulation results with the test data of the BFRP bars reinforced sea sand and seawater concrete eccentric compression short columns.The results show that there is no significant difference between the simulated value and the experimental value of the ultimate bearing capacity,and the average of relative error is 3.41%.The lateral deflection in the column simulated by finite element method,the compressive strain at the edge of concrete compression zone by finite element method and the tensile strain of BFRP reinforcement under tension by finite element method are in good agreement with the experimental results.It is shown that the numerical simulation results of ABAQUS have good accuracy.2.Finite element analysis on the sea sand and seawater concrete eccentric compression moderate long columns with BFRP bars.Effects of the eccentric compression mechanical properties of sea sand and seawater concrete moderate long columns with BFRP bars were studied.The effects of reinforcement ratio,slenderness ratio,eccentricity,strength grade of concrete,stirrup spacing on lateral deflection,the compressive strains of at the edge of concrete compression zone,the tensile strains of BFRP bars under tension and ultimate load were investigated.(1)The failure characteristics of sea sand and seawater concrete eccentric compression moderate long columns with BFRP bars are as follows: the lateral deflection occurs in the middle of the specimen along the direction of eccentric compression,and when the concrete is destroyed,there is a large deflectiondeformation in the middle part of the concrete,and the stress of the concrete in the compression area is large,and the stress is symmetrical along the length of the specimen.(2)The bigger the reinforcement ratio is,the smaller the lateral deflection of columns is;the bigger the slenderness ratio is,the bigger the lateral deflection of columns is;the bigger the eccentricity is,the bigger the lateral deflection of columns is;the effects of stirrup spacing and the strength grade of concrete on the lateral deflection of columns isn't obvious;(3)The bigger the reinforcement ratio is,the smaller the compressive strains of at the edge of concrete compression zone is;the bigger the slenderness ratio is,the smaller the compressive strains of at the edge of concrete compression zone is;the bigger the eccentricity is,the smaller the compressive strains of at the edge of concrete compression zone is;the bigger the strength grade of concrete is,the smaller the compressive strains of at the edge of concrete compression zone is;the effects of stirrup spacing on the compressive strains of at the edge of concrete compression zone isn't obvious.(4)The bigger the reinforcement ratio is,the smaller the tensile strain of BFRP tendons under tension is;the bigger the slenderness ratio is,the smaller the utilization rate of tensile strength of BFRP bars is;the smaller the eccentricity is,the smaller the utilization rate of tensile strength of BFRP bars is;the higher the strength grade of concrete is,the higher the utilization ratio of tensile strength of BFRP bars is;the effects of stirrup spacing on the lateral deflection of columns aren't obvious;(5)When the eccentricity is large,the higher the reinforcement ratio is,the higher the ultimate load is,and when the eccentricity is small,increasing reinforcement ratio has little effect on ultimate load;The effect of increasing reinforcement ratio on the ultimate load of specimens with different slenderness ratio,the strength grade of concrete and stirrup spacing is almost the same;When the slenderness ratio is small,the ultimate load increases with the increase of strength grade of concrete,and when the slenderness ratio is large,the effect of improving concrete strength grade on the ultimate load is less;The influence of concrete strength grade on the ultimate load of specimens becomes weaker and weaker with the increase of eccentricity;The effect of reducing the stirrup spacing on the ultimate load of specimens with different concrete strength grades is the same.3.According to the Design specifications and Relevant literature from both China and overseas,the calculation method of bearing capacity of sea sand and seawater concrete eccentric compression moderate long columns with BFRP bars is put forward in the paper,in which the effect of the slenderness ratio and original eccentricity on the ultimate load is considered,and the calculation results agree well with the test results.