Study On Mechanical Behavior Of Recycled Concrete Filled Square Steel Tubes Subjected To Pure Bending Under The Environment Of Acid Rain

In this paper, totally 6(recycled) concrete filled square steel tubes with different types of concrete and corrosion degrees were tested subjected to pure bending under the environment of acid rain to analyze the mechanical properties. On this basis, the model of(recycled) concrete filled square steel tubes was established. According to the research of other scholars, the calculation formula of flexural capacity of(recycled) concrete filled square steel tubes is presented.The main achievements were presented as follows:(1) This paper carried out the tests of 4(recycled) concrete filled square steel tubes subjected to the environment of artificial acid rain, and recorded of the whole process of corrosion test and corrosion thickness of steel tubes detailedly. This paper shows that the corrosion solution changes with the changes of the iron ions. In the process of corrosion, the measured corrosion thickness is close to the theoretical corrosion thickness, which further verifies the reliability of the first law of Faraday electrolysis.(2) After the corrosion test, the mechanical properties of all the components are studied, the analysis of mechanical properties of pure bending was carried from experimental phenomena, failure modes, the moment and deflection curves and the moment and stress curves. The results show that the recycled concrete-filled square steel tubes have similar failure modes with the normal concrete-filled square steel tubes, and the types of aggregate have little effect on the failure mode. With the increase of the degree of corrosion, the linear stiffness of the specimens is reduced, and the ductility is also slightly reduced. Compared to the 10% target corrosion degree specimens, the bearing capacity of 20% target corrosion degree specimens decreased significantly.(3) The models of the(recycled) concrete filled square steel tubes was established by the method of reducing the thickness of steel tubes, the relationship curves of moment and deflection curves were simulated and compared with the experiment from the aspects of bearing capacity and failure mode. Comparison shows the linear stiffness of specimens of finite element analysis is slightly larger than experiment, the numerical results are found to be in good agreement with test data in both failure models and load-deflection curves.(4) The influence of corrosion was considered by the method of reducing the thickness of steel tubes and existing simplified calculation method of bending bearing force of(recycled) concrete filled square steel tubes is used in this paper. Comparing the results of calculation and experiment, it can be found that the simplified calculation results is lower than the experimental results. It would be is a little conservative when the formula is used to calculation the(recycled) concrete filled square steel tubes subjected to pure bending under the environment of acid rain.