Analysis On Residual Deformation Of I-Section Steel Flexural Members Strengthened By Welding While Under Load

Welding reinforcement under load has been widely used in the strengthening of beams of steel structures.Relevant regulations and calculation methods for the reinforcement method are proposed in the current Chinese Standard for design of strengthening steel structure GB 51367-2019.At present,there have been many studies on the mechanical properties of steel beams strengthened by welding under load,but there are few studies on their welding residual deformation.The current welding residual deformation calculation formula in the code is reported as having problems,such as unclear basis,large deviation between calculation results and test results,and lack of detailed regulations on welding methods,so further analysis is required.Therefore,by means of experimental research,numerical simulation,analytical reasoning and other methods,this paper explains the change mechanism of welding residual deformation of steel beams reinforcd under load,and proposes amendments to the calculation formula in current code and suggestions for the construction and design.The main research works covered in this dissertation include:(1)Welding reinforcement tests of I-beams under load are carried out,and the time-history curves of the mid-span welding residual deformation and the mid-span welding residual rotation angle under different welding processes are measured.The actual welding time of each section and the non-welding time between each welding section are obtained by videotape recording of welding processes.The time-series variation mode of the mid-span welding residual deformation and the mid-span welding residual rotation angle,as well as the welding time distribution of the welding processes are obtained.(2)In view of the welding process with long weld length,many weld segments and complex welding process in this paper,a practical method for thermal-mechanical coupling analysis of welded structures with similar dimensions to this paper is proposed,and the feasibility of the finite element model is verified based on the test results.In addition,the finite element model is simplified by investigating the influence of using the average welding speed of the upper and lower flanges instead of the actual welding speed and ignoring the non-welding time on the final welding residual deformation.(3)The variation mechanism of welding residual deformation of welding reinforcing beams under load is explained through analytical reasoning and finite element calculation examples,and the deficiencies of the welding residual deformation calculation formula in current code GB 51367-2019 are pointed out.On this basis,a modification idea for the standard formula is put forward.Combined with test and FE analysis results,amendment suggestions are put forward for the calculation formula of welding residual deformation in the code.Then,example analyses are carried out for welding processes and reinforcement section type based on the proposed finite element model,and suggestions for construction and design are also put forward.The results of example analysis also showed that the proposed calculation formula has higher accuracy.