Numerical Study For The Behavior of Novel Concrete Filled Built-up Cold Formed Steel Columns Under Compression Load

concrete filled built-up cold-formed steel columns (CF-BCFSCs) have a widespread in the applications of high-rise constructions and heavy bearing structures. This paper presents a numerical study depending on finite element (FE) method using Abaqus software to study the behavior of CF-BCFSCs under axial compression load. The current study presents the numerical model taking into consideration the interaction between the steel skin and the infill concrete core, material nonlinearity, modeling of confined concrete, and geometric nonlinearity. The proposed FE model is validated by aligning its results with those obtained from a previous experimental study documented in the literature, demonstrating good agreement. A parametric numerical investigation of four innovative CF-BCFSCs was conducted to explore the impact of a wider array of variables, including cross-sectional configurations, ultimate-load capacity, cost-effectiveness, buckling patterns, the ultimate load contribution of the steel skin and the in-filled concrete core. Local and distortional buckling are the major mode of failures for most columns, while the overall buckling does not occur. Based on finite element results, the square column from U and C channels (S-U+C) produce the maximum ultimate load, and the most cost-effectiveness column, and the rectangular column from U and 𝛴 channels RU+ 𝛴 shows the highest ductility, and finally the square column from U and 𝛴 channels (S-U+𝛴) has the highest elastic stiffness.