Eccentric Compression Bahavior And Caculation Method Of A New Type Concrete Column Restrained With FRP Bars

When the reinforced concrete structure is affected by the corrosive medium,it is easy to cause steel bar corrosion,which not only directly reduces the bearing capacity of the structure,but also causes huge economic losses.In order to fundamentally solve this problem and improve the durability and performance of the structure,material replacement is considered to be the most effective technical approach.Fiber reinforced polymer(FRP)bars have outstanding performance advantages such as light weight,high tensile strength,good corrosion resistance,good fatigue resistance,and electromagnetic insulation.FRP bars are used instead of traditional steel bars to reinforce concrete structures The material can not only make the structure have the required bearing capacity,but also can fundamentally avoid corrosion and improve the durability of the structure.In order to improve the utilization efficiency of FRP bars,my research group proposed a new closed-type of stirrups winded from FRP fibers,which has strong integrity.Axial compression tests of FRP-reinforced concrete square columns with new stirrups have been carried out to verify that they have a strong restraining effect.The uniaxial stress-strain relationship constitutive model of the new stirrups has not yet been proposed,and the eccentric compression test of this type of column has not yet been carried out.This paper conducts regression analysis of the existing test data,establishes a uniaxial stress-strain model of concrete under the constraints of new stirrups,and uses this as a basis to perform the biasing performance of new FRP reinforced concrete columns from the perspective of section and member.Based on numerical simulation analysis,the calculation method of its bearing capacity is proposed.The specific research contents are as follows:(1)Regression analysis was performed on the data of 16 concrete square columns which reinforced with the new stirrups and FRP bars under the axial compression test to establish an accurate monotonic compressive stress-strain relationship considering the influence of longitudinal reinforcement,which is applicable to the new stirrup restrained concrete.(2)The finite strip method was used to compile the moment-curvature analysis program for the new type of FRP reinforced concrete columns.The parameters analysis was conducted to examine the volume stirrup ratio,the elastic modulus of the FRP longitudinal reinforcements,the strength of the reinforcement,the ratio of reinforcement and axial compression ratio of the columns of waist reinforcement on the effect on the mechanical properties of the section.The failure mode and development process of this kind of members was summarized.(3)The eccentric compression analysis program of the new type of FRP reinforced concrete columns was compiled.The calculation results were in good agreement with the test results as a whole,and some convergence check was performed to verify the accuracy of the analysis.The parameters analysis was conducted to examine the axial compressive strength of the concrete,the ratio of reinforcement,the type of FRP longitudinal reinforcement,slenderness ratio and eccentricities on the eccentric compression performance of components.(4)Based on the results of the simulation analysis,from the perspective of the internal force balance and deformation coordination conditions of the section,a calculation method for the ultimate bearing capacity of the new type of FRP reinforced concrete columns considering the restraint effect of new stirrups and the compression contribution of FRP bars in the compression zone is established.The simulation results agree well.