Flexural Behavior of CFST Beams with Plain and Sustainable Concrete Infill

Authors: Research Scholar Venugopal Burugupally, Dr Ajay Swarup

Abstract: This paper focused on flexural performance of concrete-filled steel tubular (CFST) beams with plain and green concrete infillings. The specimens, a total of thirty (30) square and rectangular hollow steel sections filled with normal mix concrete (NMC), fly ash concrete (FAC), quarry waste concrete (QWC) and low-strength concrete (LSC) were tested in basic ways, namely, under static and under cyclic bending mode. Comparative tests were drawn against unfilled hollow sections to determine the effect of composite action and of the type of concrete. It was found that NMC and FAC has the highest flexural capacity, stiffness and ductility with NMC performing better than the others by 42 percent in peak load compared to the hollow beams. Both FAC and QWC offered alternatives that were environmentally sustainable and acceptable in performance and LSC exhibited limited structural viability. Depending on the concrete type, the failure modes were characterized by ductile plastic hinging, buckling before reaching the core and core crushing. These results serve to emphasize that infill concrete characteristics are crucial to maximize flexural behavior of CFST structures and propose the green concrete mixes applicable in sustainable structures.