Research On Stability Of Circular Steel Columns Strengthened With CFRP Based On Orthogonal Design

Strengthening the steel structures by Carbon Fiber Reinforced Polymers(CFRP)has become the domestic and foreign scholar's research hot spot for it is a kind of reinforcement technologies with unique advantages.CFRP reinforcement technology is mostly used in concrete structures in practical projects,and corresponding domestic regulations have been formulated.However,the investigation of strengthening steel structures by CFRP started later and corresponding specifications are beening worked out.Basing on orthogonality to select some representative points from a comprehensive test,orthogonal experimental design is a method to study experiment with multiple factors and multiple levels.With the aid of orthogonal design,three factors of CFRP layers,eccentricity and initial load level are studied in changing the ultimate bearing capacity of circular steel tubular columns.The experimental study on CFRP reinforced compression steel columns was carried out by setting up 10 circular steel tubular columns specimens,and the failure characteristics,failure mechanism and mechanical properties of CFRP-reinforced circular steel tubular columns were studied.In addition,the analysis of the result value of the ultimate bearing capacity,load-strain and other were conducted.Based on the the numerical analysis of range and variance of orthogonal design,it is found that the factors that affecting the ultimate bearing capacity change from primary to secondary are eccentric value,CFRP layer and initial load level.This paper proposed the stability capacity calculation formula using the equivalent section method proposed by British Construction Industry Research and Information Association(CIRIA)in ‘Strengthening metallic structures using externally bonded fibre-reinforced polymers'.Then it conducted the calculation formula of in-plane stability of compressed circular steel tube column after CFRP reinforcement by MATLAB.In addition,the calculation model is established by ANSYS,and the finite element simulation of test is carried out.Finally,by comparing the experimental value,the theoretical calculation value and the simulation results,the calculation formula of the in-plane stability of loaded circular steel tube column after the modified CFRP is given.This subject is well supported by national standard ‘Design code for strengthening steel structure' and the research findings of this paper will provide theoretical and experimental bases for writing this standard.