Bearing Performance Degradation Mechanism Of Concrete Filled Thin-Walled Circular Steel Tube Column Based On Corrosion

A lot of experimental study and theoretical analyses of circular concrete-filled steel tubular column have been conducted at home and abroad, but the study on the bearing capacity degradation of circular concrete-filled steel tubular column after the corrosion needs to be further conducted. In this paper, the working mechanism and bearing capacity degradation of the thin walled circular concrete-filled steel tubular column after corrosion are studied, which is carried out from the following several aspects:1. The artificial simulation in laboratory on the underground roadway support engineering environment has realized the laboratory manual accelerated corrosion test with a high fitting of the engineering environment; the study has shown that once the steel components suffered from corrosion, the corrosion rate will continue to increase with the time passing.2. Experiment research on 20 thin-walled circular concrete-filled steel tubular columns are conducted, in which, 14 components are conducted the artificial accelerated corrosion test, the relationship between the corrosion degree, diameter-thick ratio, confinement coefficient, axial compression and the ultimate bearing capacity of short column, it is found that Along with the increase in corrosion degree and diameter-thick ratio, the bearing capacity degradation trend of the component slows down. Experiments show that the axial compression failure pattern of thin-walled circular concrete-filled steel tubular short columns basically is the shear failure, with the decrease of the thickness, the plastic deformation ability of components decreases. At the same time, the working mechanism of axial compression of thin-walled circular concrete-filled steel tubular column is discussed.3. The etch pit formed by corrosion causes a thin spot of steel tube on core concrete tight hoop constraint function, and the stress concentration of component is formed at the etch pit, the component is more likely to occur damage in this thin spot; the impact of corrosion degree and length-diameter ratio, L/t and other parameters on mechanical properties of long column structure is discussed. With the increase in corrosion rate, the corrosion of the component changes from uniform corrosion to serious local pit corrosion, which is also a major cause for the drop increase in component bearing capacity with the increase in corrosion rate.4. A finite element analysis model of axial compression circular concrete-filled steel tubular column is established. Through calculation, under the condition of axial compression, the load- deformation relation of thin-walled circular concrete-filled steel tubular column, the impact rule of corrosion degree on the mechanical properties of components are obtained, which is basically consistent with the test results in the laboratory.5. On the basis of the results of numerical analysis, an axial compression short(long) column mechanical analysis model of the thin- walled circular concrete-filled steel tubular column is established, the formula of ultimate bearing capacity of thin-walled circular concrete-filled steel tubular short(length) column is obtained, and the design value of bearing capacity of the thin- walled circular concrete-filled steel tubular short(length) column is proposed; Based on the impact of the steel tube corrosion, the calculation formula of ultimate bearing capacity of the thin walled circular concrete-filled steel tubular axial compression short column after corrosion is obtained.