Research On The Influence Of BFRP Reinforcement On The Bearing Capacity Of Freeze-Thaw Damaged Concrete Short Columns

The fiber reinforced composite(FRP)reinforcement method has the advantages of simple construction and obvious reinforcement effect.Compared to other fiber reinforced composites,basalt fiber reinforced composites(BFRP)have the advantages of superior comprehensive performance and high cost performance(the price is one fifth of carbon fiber),and are gradually replacing traditional fiber reinforced composites in the field of civil engineering reinforcement.In seasonally frozen regions of China,freeze-thaw cycles alternate frequently.Freeze-thaw damage to concrete structures is difficult to avoid,which seriously affects the use function and life of concrete structures,so attention should be paid to it.Due to the fact that the research on BFRP confined concrete columns is mostly in the experimental stage,which consumes a lot of manpower and material resources,and many experimental data cannot be reliably collected,theoretical analysis and calculation and finite element analysis methods need to be conducted on the basis of experimental data to analyze BFRP confined freeze-thaw damaged concrete columns.The main research contents and conclusions are as follows.Through three types of BFRP cloth wrapping layers(0,2,and 3 layers)and four freeze-thaw cycles(0,25,50,and 75 times),the influence of BFRP cloth reinforcement layers on the bearing capacity of concrete columns with different freeze-thaw damage was systematically studied.The results indicate that:(1)After undergoing freeze-thaw cycles,the ultimate bearing capacity of concrete columns significantly decreases,while the ultimate displacement slightly increases.(2)BFRP reinforcement effectively improves the ultimate bearing capacity of concrete columns subjected to freeze-thaw cycles,and also significantly increases the ultimate displacement.(3)Through experimental phenomena and data analysis,it was found that additional reinforcement should be applied at the end to achieve better reinforcement effects.(4)Using ABAQUS and selecting appropriate material constitutive models,12 finite element models were established based on experiments.The simulation results were in good agreement with experimental and theoretical calculations.(5)Regression was performed on the experimental data of plain concrete short columns with four unreinforced freeze-thaw cycles to obtain the uniaxial compressive stress constitutive relationship of freeze-thaw damaged concrete in this experiment.After considering the effective constraint area division of FRP constrained prisms,the ultimate stress formula of BFRP constrained concrete columns and the uniaxial compressive stress constitutive relationship of freeze-thaw damaged concrete were introduced,and a formula for the ultimate bearing capacity of BFRP constrained freeze-thaw damaged concrete short columns was established.