Numerical investigation of 4-point bend test of thin-walled regular hexagonal CFST beam

Concrete-filled steel tube (CFST) is a composite structural member composed of a steel tube and concrete in which concrete is filled inside the steel tube. CFST beam has been studied by different researchers for different shapes like square, rectangular, circular, elliptical etc. for their flexural performance. Study on 4-point bend test of thin walled regular hexagonal CFST beam for single skin by changing its strength of concrete from 20 MPa to 35 MPa using ABAQUS software has not been done so far. The finite element analysis (FEA) model has been validated using experimental data of square and rectangular CFST beam from existing literature. In the model, nonlinear material properties of steel, contact interactions, and geometric influences are taken into account so as to get the perfect model. The current paper studied the performance of hexagonal shaped CFST beam for different strength of concrete with the variation from 20 MPa to 35 MPa and steel thickness(t) = 2.5mm which comes under class 4 section of Eurocode 3 (Part 1-4). The ultimate moment capacity of the beam increases by 6.33%, 6.84%, 5.78% when the strength of concrete increases from 20 to 25, 25 to 30, 30 to 35 MPa respectively. It has been found that steel yields more in the bottom part of the CFST beam when lower strength of concrete is used comparing to higher strength of concrete. Local buckling could be observed in bending test of thin-walled hexagonal CFST beam.