Research Progress on Mechanical Properties of Concrete-Filled Steel Tube Members Under Corrosive Environment

Concrete filled steel tubes(CFST) are easy to fall off the rust layer in the process of transportation and construction, and they are in service under the action of corrosive gas, liquid and soil, which further aggravates the corrosion of steel tube wall, causing section loss and deterioration of steel performance. After corrosion, the overall bearing capacity, plastic deformation capacity, combined elastic modulus and constraint performance of core concrete are reduced, and the risk of overall structure failure is increased.
To fully understand the development status of CFST after corrosion, the static performance, seismic performance and finite element analysis of corroded CFST were compared and summarized from three aspects:microscopic corrosion morphology, mechanical properties of macroscopic components and related theoretical calculation methods, and the research on the mechanical performance of corroded CFST was prospected.
Based on the analysis of the current research, the conclusions and prospects are as follows:the research on the corrosion morphology of CFST can realize the high-precision three-dimensional reconstruction of the corrosion morphology of concrete-filled steel tube through the three-dimensional surface scanner. The influence of the distribution law of corrosion pit size, shape and depth on its mechanical properties can be obtained through the reconstruction of corrosion morphology. The research on the static performance of CFST after corrosion mainly focuses on the axial compression, axial tension and eccentric compression performance of CFST after uniform corrosion. The study of axial compression bearing capacity of corroded CFST shows that the calculation of bearing capacity based on superposition theory is more accurate than that of unified theory. At present, there are few studies on the mechanical properties of c CFST after local corrosion. Although the weight loss rate caused by local corrosion is very small, it will cause stress concentration, buckling in advance and bearing capacity reduction of components, which seriously threatens the safety of structures. It is therefore necessary to increase research in this area. The study on the seismic performance of corroded CFST columns shows that when the axial compression ratio is constant, the higher the corrosion rate is, the greater the decrease in the bearing capacity is, and the energy dissipation capacity of the corroded specimens after yield decreases rapidly. The research on the corrosion test of CFST mainly adopts the methods of electric accelerated corrosion, salt spray corrosion and mechanical groove simulation. The salt spray corrosion can better simulate the actual seawater corrosion through the test, and establish the correlation between the test corrosion and the actual corrosion environment, which can provide more valuable reference for future research. In the study of the finite element simulation method of CFST after corrosion, the wall thickness reduction method, material reduction method, birth and death element method, double shell element method and random pitting method are often used in steel tube corrosion. The study shows that the stress concentration in the corrosion pit area causes the change of failure mode and the strength decreases significantly. The random pitting method realizes the rapid geometric modeling of a large number of pitting examples. The form and distribution of pitting have a significant influence on the fatigue damage of components, and its randomness cannot be ignored when studying fatigue problems such as crack propagation. There are some differences between the random corrosion and the actual corrosion morphology. In the follow-up study, it is the key to consider the correlation between the simulated random pitting method and the actual corrosion morphology of the project. It is suggested to increase this research to realize the refined finite element simulation of the mechanical properties of CFST after corrosion.
This article will introduce the current research situation, discuss and summarize the corrosion morphology, mechanical properties and finite element simulation methods of corroded CFST members, and give relevant suggestions for further research in the future.