Flexural behavior of lightweight concrete and self-compacting concrete-filled steel tube beams

The study presents a comparative experimental analysis of the flexural behavior of lightweight concrete and self-compacting concrete filled square steel tube beams subjected to pure bending. A total of 20 specimens including eight lightweight concrete-filled steel tube (LWCFST) beams, eight self-compacting concrete-filled steel tube (SCCFST) beams, and four hollow steel tubes were tested. The main parameters varied during the experiment include (1) type of concrete core, lightweight concrete (LWC), and self-compacting concrete (SCC); (2) width to thickness ratio; and (3) confinement factor (ξ). The flexural capacities, flexural stiffness, ductility, failure modes, deflection curves, and bending moment versus mid-span deflection curves were examined. Several performance indexes were used to discuss the flexural strength, stiffness, and ductility of the tested beams. The test results revealed that LWC and SCC significantly improved the overall flexural behavior of square hollow steel tubular sections. The results indicated improvements in flexural strength, stiffness, and ductility. Furthermore, a comparison was performed, and the findings indicated that LWCFST beams exhibit increased flexural stiffness, comparable moment resistance, and lower ductility when compared to SCCFST beams. The moment capacities and flexural stiffness were compared with the predicted values by using various design codes, and the comparisons indicated that all the design codes are conservative with respect to the estimation of the moment capacity. However, all the design codes are not conservative with respect to the prediction of the serviceability level flexural stiffness. The test results and comparisons motivate application of LWCFST and SCCFST beams as a potential alternative for normal weight CFST beams.