Mechanical behavior of concrete filled steel tubular columns with high strength materials subjected to various compression loading scenarios

This study investigates the compressive performance and mechanical behavior of concrete filled steel tubular (CFST) columns constructed with high strength materials under various compression loading scenarios. Thirty specimens, including CFST columns and hollow steel tubes, were evaluated through finite element models (FEMs) in ABAQUS using nonlinear 3D elements to capture the concrete-steel interaction. The materials used had yield strengths (fy) from 455 to 525 MPa and compressive strengths (f′c) of 70 to 90 MPa. The CFST columns were subjected to three distinct loading scenarios: compression on the entire column section (CFE), on the concrete core alone (CFC), and on the steel tube alone (CFS). For comparison, hollow steel tubes (EST) were also tested under compressive loads. Results indicated that loading scenarios significantly affected the columns’ compressive performance. The highest compressive strength was observed under CFC scenario, followed by CFE, where the steel tube effectively confined the concrete core. CFS scenario produced the lowest strength, similar to EST specimens, where the concrete primarily stabilized the steel tube. Enhanced yield strength (fy) and compressive strength (f′c) notably increased CFST compressive strength in both CFC and CFE conditions. The study also found that existing design codes, including EC 4-04, AISC 360-22, and AS/NZS 2327-17, are conservative when predicting the compressive strength of CFST columns using high strength materials.