Mechanical Properties Of LRS-FRP Confined Pre-damaged Members Subjected To Monotonic Axial Compression

In recent years,Fiber Reinforced Polymer(FRP)have been widely used in the field of reinforcement of concrete structure because of its advantages of corrosion resistance,light weight,high strength,fatigue resistance,convenient construction,good chemical stability,and low maintenance costs.However,currently several mainstream FRP materials(mainly referring to CFRP/GFRP/AFRP)are limited in seismic reinforcement due to their high elastic modulus and low tensile strain at break,whereas the characteristics of Large-Rupture-Strain FRP(LRS-FRP)with low elastic modulus and large tensile strain at break just make up for the deficiency of mainstream FRP materials.Therefore,the research of LRS-FRP reinforcement performance is the sublimation of FRP reinforcement technology of concrete structure.The purpose of this paper is to provide theoretical support for the maintenance and reinforcement design of deteriorating structural columns and to establish a perfect theoretical system for the seismic design of deteriorating structural columns.Considering the effects of load-induced damage and rust damage,the mechanical properties of LRS-FRP confined pre-damaged members have been systematically studied.The main work results are as follows:(1)Aiming at the monotonic axial compression test of LRS-FRP confined load pre-damaged columns,the influences of load pre-damaged grade and constraint stiffness on the failure mode,ultimate strength,ultimate strain and stress-strain relationship of concrete columns were analyzed.Besides,the strength loss index was determined.(2)On the basis of the monotonic axial compression test of LRS-FRP confined load pre-damaged columns,the ultimate strength model,ultimate strain model and stress-strain constitutive model of the LRS-FRP confined load pre-damaged columns were proposed.(3)Aiming at the monotonic axial compression test of LRS-FRP confined corroded reinforced concrete columns,the influences of factors such as steel corrosion rate andconstraint type on the failure mode,ultimate load,limit displacement,and load-displacement relationship of reinforced concrete columns were analyzed.The enhancement mechanisms of constraint effect with CFRP and LRS FRP were compared as well.Furthermore,the buckling behavior of the steel bar under LRS-FRP and CFRP constraint and the effect of the buckling of the bar on the rupture strain of FRP were discussed.