Research on the Influence of Residual Stress on the Stability of BS700 High Strength Steel Welding Box Section Columns Fabricated By Channel Sections

High-strength steel has been used in more and more projects because it can reduce the amount of structural steel and resource consumption, but the research on the stability of high-strength steel members is still relatively lacking, and residual stress is an important factor affecting the stability of members. BS700 high-strength steel(nominal yield strength is 700 MPa) has no section steel, so the steel plate is first cold-formed into a channel-shaped section member, and then butt-welded to form a box-shaped section member. However, the welding will generate residual stress in the section of the member, and the research on the influence of welding residual stress on the stability of BS700 high-strength steel box section columns fabricated by welding channel sections is still a lack of relevant information. This paper studies this problem by means of experimental and numerical analysis methods, in order to understand the effect of residual stress on BS700 high-strength steel box section columns fabricated by welding channel sections impact on stability. The mechanical property parameters of BS700 high-strength steel material were obtained through material tensile test. With the help of tensile test, the stress release coefficient when the member that opened was obtained. The blind hole method was used to test the residual stress of the middle section of the BS700 high-strength steel box section columns fabricated by welding channel sections, and the residual stress value of the relevant points on the section was obtained. Combined with the existing research results, the residual stress distribution model of BS700 channel-butt-welded box-section members was proposed. With the help of the finite element analysis software ANSYS and its APDL programmable language, a nonlinear buckling analysis model that can introduce geometric defects and residual stress was written. The model was used for nonlinear buckling analysis of 68 components with and without residual stress. The 68 components simulated the conditions with slenderness ratios of 15, 20, 30, 40, 50, 60, 70, 80, 90, 100 and the cross-section width-thickness ratios are 10, 15, 20, 25, 30, 35, 40, and 50, respectively. The effect of residual stress on the stability of BS700 high-strength steel box section columns fabricated by welding channel sections under different width-thickness ratios and different slenderness ratios was studied. Through the research, it is found that there is residual tensile stress at the weld and corner, and residual compressive stress at the rest. The maximum residual tensile stress level at the weld is about 0.76 times the yield strength, and the maximum residual compressive stress at the middle of the web is about 0.14 times the yield strength. On the basis of the existing research, a polyline residual stress distribution model is proposed, which is in good agreement with the experimental results; the residual stress has an influence on the stability coefficient of members under different width-to-thickness ratio conditions, and the overall trend is with the width-to-thickness ratio. Increase, the influence of residual stress gradually decreases, mainly due to the phenomenon of local elastic buckling of the member under the condition of large width-to-thickness ratio; the effect is relatively small when it is small or large. When the slenderness ratio is between 20 and 70, the residual stress has a great influence on the stability coefficient of the member. By comparing the critical slenderness ratio when the plate is partially buckled, it is found that the two overlap. In the stability design, the members in the range of medium slenderness ratio are relatively sensitive to residual stress, so this influencing factor should be paid attention to in the process of component stability design.