Finite Element Study On The Ultimate Bearing Capacity Of Concrete Filled Steel Tube With Initial Stress

In the actual project, the concrete-filled steel tube structure is usually set up the steel tube firstly, then pouring concrete. In order to speed up the construction progress, sometimes several layers of steel tube will be set up before pouring concrete. Then the empty steel tube will appear vertical compressive stress due to the weight of the upper and the effect of construction load. This vertical compressive stress is called steel tube initial stress, short for initial stress. For some of the steel tube, in which the bearing capacity is insufficient or aging need to be reinforced. But sometimes steel tube can not unloading the load on the steel tube because of the constraints, also can produce initial stress in steel tube. Initial stress can reduce the bearing capacity of the whole structure. Consequently, initial stress lead to the entire structure be unsafe. There is no calculation formula of bearing capacity of concrete filled steel tubular components under the initial stress in our country’s code.This article is mainly talking about the analysis of the mechanical performance of the concrete-filled steel tube structure under the initial stress by general finite element software-ABAQUS. In the article, some factors have been analyzed, including the initial stress ratio, slender proportion, eccentricity ratio and so on. According to the research, the initial stress of steel tube makes the deformation and deflection of concrete-filled steel tube heightened, while making the bearing capacity reduced. Among many factors that affect the coefficient of initial stress, the initial stress ratio, slenderness ratio and eccentricity ratio play important roles. The larger the slenderness ratio, the greater of the initial stress ratio, the stress coefficient is larger. In a certain range of eccentricity, the smaller slenderness ratio, the larger eccentricity ratio, the stress influence coefficient is smaller. When the slenderness is larger, the larger the eccentricity ratio, the influence of the initial stress coefficient may be greater. These factors have an effect on the bearing capacity of the concrete-filled steel tube. The simplified calculation formula of the concrete-filled steel tube’s capacity under the initial stress is put forward. In addition, how to use the influence coefficient in the code has been illustrated in the article.In addition, whether the finite element analysis’ s results are accuracy or not, it need to be tested by experiments. So I have compared the finite element analysis’ results with other’s experimental research results. The comparison show that the finite element analysis’ s results approximately agree with the experimental. The simulation results of this paper can provide the construction of the reference for practical engineering staff as.