Compressive Behavior And Size Effect Of Predamaged Concrete Confined With Basalt Fiber-reinforced Polymers

In recent years,due to the frequent earthquakes and erosion factors,the building structure has suffered various degrees of damage,the reinforcement and maintenance have gradually become a research hotspot in the field of civil engineering.Fiber reinforced polymer(FRP)has attracted more and more attention in the field of civil engineering because of its light weight,high strength,convenient construction and good corrosion resistance.It has gradually become a commonly used building material in various forms of engineering structural reinforcement.With the enhancement of people’s environmental awareness,green sustainable technology has become a new development direction.Basalt fiber-reinforced polymer(BFRP)has excellent mechanical properties,and also has the characteristics of green energy saving,rich raw materials,with broad development and application prospects.At present,the research on the mechanical properties of FRP-confined concrete is mainly concentrated on small-sized specimens.There is still a big gap in the study of axial compression performance and size effect of FRP-confined concrete.Therefore,the axial compression behavior and size effect of BFRP-confined concrete are investigated in this paper.In addition,acoustic emission(AE)is used in the axial compression process for damage monitoring.The main research contents are as follows:(1)Experimental study on the performance of BFRP materials.The tensile properties of BFRP sheets were obtained by tensile test of BFRP sheets,and the properties of tensile strength,elastic modulus,elongation at break and stress-strain relationship were obtained.(2)Experimental study on axial compression performance of BFRP-confined concrete.In this paper,the BFRP layer number,the specimen size and the initial damage level are taken as the research parameters.The axial compression performance tests of 48 concrete cylindrical specimens are carried out.The failure mode,strength ductility,stress-strain curve and energy dissipation performance of BFRP-confined concrete are analyzed.(3)Study on the ultimate stress model,ultimate strain model and stress-strain relationship model of BFRP-confined intact and predamaged concrete.In this paper,the existing classical models are compared and analyzed.The ultimate stress model,ultimate strain model and stress-strain relationship model for BFRP-confined intactconcrete are proposed.Based on the area damage evaluation index and stiffness damage evaluation index,the ultimate stress model,ultimate strain model and stress-strain relationship model of BFRP-confined predamaged concrete are established.(4)Study on the size effect of BFRP-confined concrete.The failure mode,strength and strain capacities of BFRP-confined concrete were analyzed by visual analysis and one-way variance method.The conclusion of size effect was obtained from the statistical point of view,and the ultimate stress model of BFRP-confined concrete considering the influences of size effect and initial damage level is proposed.(5)AE monitoring and evaluation of the damage process of BFRP-confined concrete.The AE signal source and AE event characteristic parameters of BFRP-confined concrete were analyzed.The damage evolution process and failure mode of BFRP-confined concrete were studied by b-value method and RA-AF correlation method.The damage evolution law of BFRP-confined concrete during axial compression loading is obtained.