Experimental Study And Finite Element Analysis About The Effect Of Longitudinal Reinforcement Types On Compressive Behavior Of Reinforced Concrete Column

In recent years,FRP reinforced concrete structures formed by FRP bars instead of steel bars have become a way to solve the problem of insufficient durability of reinforced concrete structures in harsh environments.However,the low elastic modulus,large cracks and deflections,brittleness of failure and the absence of yield platforms similar to steel bars of FRP reinforced concrete,which limits the development of FRP bars concrete structures.SFCB combines the advantages of steel bar and FRP bar.It has stable secondary stiffness and high modulus of elasticity.SFCB has become the focus of domestic and foreign scholars.In order to study the influence of longitudinal reinforcement types on the compressive performance of concrete columns,we designed and tested tour groups of concrete columns with different longitudinal reinforcement(one group of reinforced concrete columns,one group of FRP reinforced concrete columns and two groups of SFCB concrete columns of different types;three specimens of each group,preliminarily designed as three types of axial compression,small eccentric compression and large eccentric compression).The influence of longitudinal reinforcement type on the bearing capacity,failure mode,crack and deformation of compressive members of concrete columns was investigated.The model was established by ABAQUS finite element software.The influence of concrete strength,eccentricity,reinforcement ratio and SFCB type on compressive performance of SFCB concrete columns were supplemented and analyzed.The conclusion was as follows:(1)The tensile stress-strain curve and the compressive stress-strain curve of SFCB were all two-segment broken lines.The relationship before and after the yield were linear.The compressive yield strength of SFCB was about ninety-five percent of the tensile yield strength and the compressive ultimate strength of SFCB was about thirty-seven percent of the tensile ultimate strength.The tensile stress-strain curves and compressive stress-strain curves of BFRP tendons were all linear.The ultimate compressive strength was about sixty-nine percent of the ultimate tensile strength.(2)The ultimate bearing capacity of reinforced concrete columns under axial compression was smaller than that of SFCB reinforced concrete columns and FRP reinforced concrete columns.The ultimate bearing capacity of S6B20 concrete column was greater than that of S6G24 reinforced concrete column.(3)Under eccentric load,the ultimate bearing capacity of SFCB concrete column was smaller than that of reinforced concrete column,which was close to that of FRP reinforced concrete column.The deflection of' SFCB concrete columns was larger than that of reinforced concrete columns and smaller than that of FRP reinforced concrete columns.Under the same eccentricity,the utilization of SFCB was greater than the that of FRP bar,and the utilization of-S6G24 was greater than that of S6B20.Under the quasi-permanent combined load and deflection limit,the strength utilization ratio of the reinforced concrete column was greater than that of the SFCB concrete column and was larger than the BFRP concrete column.The strength utilization rate of the tensile reinforcement of S6B20 concrete column was less than that of S6G24 concrete column,and the strength utilization rate of the compression side reinforcement was greater than that of S6G24 concrete column.Under the crack width limit,the strength utilization rate of the ribs on both sides ot the S6B20 concrete column was less than the strength utilization rate of the S6G24 reinforced concrete.(4)The applicability of the ABAQUS software was verified.Analysis of four parameters(concrete strength,eccentricity,reinforcement ratio and SFCB type)on the compression performance of SFCB concrete columns was supplemented:the concrete strength increased,the deflection in the column increased and the ultimate bearing capacity increased;the eccentricity increased,the deflection in the column increased and the ultimate bearing capacity decreased;the reinforcement ratio increased,the deflection in the column decreased and the ultimate bearing capacity increased;when the SFCB outer cladding material was the same,the increase of the inner core reinforcement diameter was beneficial to improve the bearing capacity and deformation resistance of the SFCB concrete column.When the diameter of the inner core bar was the same,the ultimate load from the largest to the smallest was S6C20 concrete column,S6G20 concrete column and S6B20 concrete column.The deformation in the column from the largest to the smallest was S6C20 concrete column,S6B20 concrete column and S6G20 concrete column in the order of failure.