Flexural Strength Evaluation of Multi-Cell Composite T-Shaped Concrete-Filled Steel Tubular Beams

The multi-cell composite T-shaped concrete-filled steel tubular (MT-CFST) element is an innovative structural form. It has great potential for construction applications because of favorable advantages over traditional composite elements. The flexural strength of MT-CFST beams was investigated in this study to provide recommendations in line with existing design codes. First, formulations to evaluate the flexural strength of MT-CFST beams were derived based on the Unified Theory and plastic stress distribution method (PSDM). For the Unified Theory-based formula, a modified confinement effect factor that considers the shape of a cross-section was proposed. An experimental study on the flexural behavior of six MT-CFST beams as well as two hollow section counterparts was conducted. The influence of bending moment direction, concrete infill, wall thickness, and cross-section sizes were investigated. The accuracy of the proposed formulations was verified against the test results and numerical results from finite element modeling. The comparisons showed that the formula in line with the Unified Theory provided more accurate predictions with reasonable conservatism for the studied MT-CFST beams.