Behavior of axially loaded concrete-filled steel tubular columns with multi-region localized corrosion

Localized corrosion can occur on multiple areas of the outer surface of square concrete-filled steel tubes (CFSTs), which can significantly compromise structural safety during service. The nature of localized corrosion is characterized by significant stochasticity, manifesting as spatial dispersion in both location and extent, coupled with irregular morphology. To evaluate the influence of multi-region localized corrosion in terms of area, position, and degree, an experimental program was conducted involving seven square CFST columns containing simulated local corrosion defects, alongside two uncorroded reference specimens subjected to axial compression. The experimental phenomenon, ultimate strength, and lateral deflection profiles of tested specimens were obtained. Numerical models were developed and validated against experimental results, then extended to incorporate the irregular profile and uneven surface of corrosion morphology. Finite element analysis indicated that single random corrosion damage can be considered a regular defect region with an even surface for axially loaded square CFSTs. The influence of corrosion dimensions and the position of single and multiple corrosion regions on axial compression performance was probed through a parametric investigation. It was indicated that the controlled section of the square CFST was significantly influenced by the corrosion locations. If the controlled section remains intact, the corrosion effect can be negligible, and if the controlled section is corroded, the ultimate strength can decrease by 28 %. A controlled section-based method was proposed to predict the ultimate strength, demonstrating reasonable accuracy.