Flexural behavior of steel tube beams infilled with normal, lightweight and recycled aggregate concrete: A review

Cold-formed steel sections face the issues of local buckling due to the smaller thickness and the presence of free edges. Concrete-filled steel tube (CFST) is considered a promising solution for enhancing structural performance and preventing the occurrence of local buckling for steel tubes. In addition to the conventional CFST members, recent research has focused on replacing the infilled concrete with lightweight concrete and recycled aggregate concrete. Incorporating lightweight concrete aims to reduce the overall self-weight of the composite members, whilst recycled aggregate promotes the utilization of waste materials, making CFST members more environmentally friendly. The presence of internal stiffeners further increased the loadbearing capacity and stiffness of the CFST members. This study aims to examine the current research on the flexural behavior of CFST beams, with a specific emphasis on the type of infilled materials and the impact of internal stiffeners. The reviews cover experimental findings, numerical simulations, and analytical methods for the CFST beams. The insights drawn from this review aim to guide the current research gap and future research directions on CFST beams.