Mechanical behavior of coral concrete-filled aluminum alloy square tube columns subjected to eccentric loading

Coral aggregate concrete (CAC), a composite material consisting of coral aggregates, ordinary Portland cement, and seawater, demonstrates significant potential for application in island buildings. However, the use of seawater introduces corrosive ions such as Cl^- and SO₄^2- into CAC, leading to the corrosion of reinforcement. In recent years, the integration of CAC with aluminum alloy square tubes has emerged as an improved anti-corrosion strategy due to the excellent corrosion resistance of aluminum alloy. In this study, 15 CAC-filled aluminum alloy square tube columns (CCAT) were fabricated, considering three concrete strengths (C20, C30, and C40), three eccentricities (e = 20 mm, 40 mm, and 60 mm), and three tube thicknesses (t = 2 mm, 4 mm, and 6 mm). The ultimate bearing load, ductility, and stiffness were investigated in relation to these variables, respectively. Additionally, a finite element analysis (FEA) model was developed to simulate the eccentric compressive behavior of CCAT, and a new eccentric bearing capacity model was proposed. The results indicated that increasing the aluminum alloy tube thickness enhanced the ultimate bearing load and stiffness, while increasing the eccentricity reduced both stiffness and bearing capacity. Furthermore, the findings were validated through FEA, and 12 extended analysis results were also presented. A novel bearing capacity model, incorporating equivalent constraint theory, was established. This model demonstrated accurate predictions compared to existing code models.