Experimental Study And Numerical Simulation Of High Strength Concrete Columns Strengthened With GFRP Based On Design Specification Comparison

A large number of houses, bridges and other structures are damaged by earthquakes, fires and other natural disasters in the design reference period. Structures are aging caused by prolonged use. The function of building structures change. The construction quality is not qualified to reach the design strength of concrete. These above problems will lead to the structure in a state of insecurity and affect the normal use. Demolition and reconstruction will result in waste of resources and pollute the environment. Therefore, the maintenance and strengthening of the structure is an important research topic in civil engineering. Compared with traditional reinforcement methods, fiber composite material has the advantages of high strength, high elasticity, light weight, corrosion resistance, high temperature resistance, fatigue resistance, good thermal insulation performance, and ease of construction,the assurance of construction quality,which are applied to the Reinforcement of structure engineering more and more.At present, domestic and foreign scholars have done a lot of research on axial compressive behavior of concrete columns reinforced with carbon fiber reinforced composites. However, the modern engineering structure has developed to the super high and large span. The requirement for concrete strength is higher and higher. In practical engineering, the concrete columns are mostly in the eccentric stress state, and the axial compression members seldom appear. Compared with CFRP, GFRP has the advantage of low price and large strain. Therefore, the research of GFRP reinforced high strength concrete column has more engineering application value.Experimental study and finite element analysis on mechanical behavior of 10 GFRP strengthened high-strength concrete columns. The ultimate bearing capacity, failure mode and ductility of the specimens under different reinforcement methods are studied in depth. The reinforcement methods and calculation methods of different countries in different codes are analyzed. Specific research work is as follows:(1) Study on the failure process and failure mode of 10 high strength concrete columns under eccentric loading. Among them,2 are contrast column,8 are GFRP strengthened column. The variation parameters of the test are the eccentricity, the number of GFRP and the way of pasting. Compare the effects of three kinds of reinforcement methods(longitudinal bending strengthening, lateral restraint reinforcement and mixed reinforcement) on the ultimate bearing capacity, ductility, load displacement curves, concrete ultimate compressive strain, and longitudinal and transverse FRP strain of different eccentric specimens. The results indicated that, via the transverse reinforcement of GFRP sheets, the ultimate strength of small eccentric compression concrete columns is enhanced and the ductility of concrete columns improved, and the transverse reinforcement have little influence on the ultimate strengths of large eccentric compression concrete columns. the longitudinal reinforcement, the ultimate strength of large eccentric compression columns is enhanced, but the ductility of concrete columns declined. the hybrid reinforcement is best for large eccentric compression, but have little advantage on small eccentric compression.(2)The finite element software ANSYS was used to simulate the nonlinear finite element analysis of 10 specimens in the whole process. Some valuable formations can be obtained, such as ultra carrying capacity, loading-deflection curve of specimens, the fiber strain distribution of GFRP and distribution of concrete crack at some time. The simulation results are in good agreement with the experimental data.(3) Analysis and comparison of different specifications of the relevant sections of FRP reinforced concrete. The specifications include technical code for infrastructure application of FRP composites, trengthening concrete structures published by ACI committee 440,concrete society and Chinese code for design of strengthening concrete structure. The comparison of FRP confined concrete constitutive relation, the method of reinforcement and the calculation method of bearing capacity of eccentric compression column are compared. Apply different specifications for the calculation.