Study On Design Of The Welded Thin-walled Box Section Column Under Axial Pressure

Steel has the advantage of high strength, light weight, good mechanical properties, etc., along with the development of steel structure, welded thin-walled box section member structure in more and more widely applied. Welded thin-walled box-shaped member is made of four steel plates which welded together; cross-sectional moment of inertia of large cross-section has a good stability, suitable for large span structural member. In the application process, welded thin-walled box section has a thin plate with broad width, and it is often difficult to guarantee local stability in performance. China’s current "Design of Steel Structures" GB50017-2003in for welding thin-walled box member only made generous provisions about the limits of thickness ratio, the case for the thickness ratio which out of specification, and did not give the appropriate design methods. Engineering staff member in order to obtain better performance, or subject to conditions, they had to be overrun sectional thickness ratio, in order to solve this problem, this paper carried out relevant research work.This paper carried out a detailed analysis and discussion about the stress mechanism of welded thin-walled box section member in theoretically, pointed out the force model of a single block board member and deduced theoretical solution. For the lack of current specification, this paper described the effective section method; the effective yield strength method and the parametric design method which applied to the situations overrun the thickness ratio of specification.Using the finite element software ABAQUS, studied the ultimate bearing capacity of thin-walled welded box-section for short column model of axially loaded under the influence of different factors. This paper focused the components of different thickness ratio, different initial defect, stiffeners and other factors on the ultimate bearing capacity, local stability, stiffness and other problems. The results showed that:(1) As the thickness ratio increases, the ultimate load of component decreases, beyond the specification limit, the component performed a sudden destruction of local instability; initial defects had a significantly effect on the ultimate bearing capacity, local stability and stiffness of the components;(2) The setting of stiffeners had changed the buckling mode of plate, indirectly enhanced the member’s ultimate capacity, ensured the local stability, and improved the initial stiffness; The presence of stiffener can significantly reduced the components sensitivity of the initial defect; different sizes form of stiffeners played the same role in the components basically, and proposed the design method in accordance with the minimum requirements of the design specification;(3) Generously, the thickness ratio had no influence on the initial stiffness of the component, to those who do not directly bear the load, the bearing load is very small or the stability in cross-section from the main control component that can be designed out of specification, the limit of thickness ratio can be enlarged appropriately;In the basic of finite element analysis, recommendations had made on the design of the thin-walled welded box-section, and on the component test piece model to further verified by experiment.