The Effect Of Elevated Temperature On Welding Residual Stress

Residual stress will be changed due to the influence of temperature, which will affect the load bearing capacity of steel column subjected to fire. However, the effect of residual stress on load bearing capacity at elevated temperature still used the residual stress at room temperature in Chinese Code CECS200 : 2006, this will affect the accuracy of fire resistance of steel column.In order to evaluate the influence of residual stress on fire resistance of steel columns, and provide a basis for the simulation of stability capacity, the process of steel column subjected to fire was simulated using electric furnace. The residual stress distribution at room temperature and after 200 ℃ ~800 ℃ in welding H-section and box-section steel columns made of Q235 and Q460 steel was obtained by sectioning method. Residual stress models were proposed according to the test results. In addition,the variation of residual stress subjected to fire was simulated by finite element method and the reduction factors of residual stress at elevated temperature were obtained. The main research scopes and conclusions covered in this paper are as follows:(1) 20 steel columns were numbered according to steel grades, section shapes and target temperatures. 16 columns were subjected to different temperatures in the furnace,while the remaining 4 columns were kept at room temperature as contrast. Residual stress distribution of all the steel columns were obtained by sectioning method, and residual stress models of different sections were proposed.(2) After compared with the residual stress distribution at room temperature, it was found that the residual stress in steel columns was released after temperature exposure,the higher the temperature was, the lower the residual stress would be. The reduction factors of residual stress after different temperatures were obtained from the test data by comparing the residual stress at room temperature with that at elevated temperature.(3) The variation of welding residual stress subjected to fire was simulated by ANSYS. The results obtained by FEM agreed well with test results. It was found that creep has great influence on stress change of steel structure at elevated temperature and should be taken into account.(4) The reduction factors of residual stress at elevated temperature based on the finite element analysis were obtained by comparing the residual stress at elevatedtemperature with that at room temperature, both for welding H section and box section.(5) The stability bearing capacity of steel columns at elevated temperature was analyzed by ANSYS, in which process the residual stress at elevated temperature was taken into account. It was proved that the finite element result of steel column stability bearing capacity were slightly higher than the result of Chinese Code CECS200:2006,while both of them were higher than the results of EC3 and AISC360-10.