Flexural behavior of concrete-filled steel tube composite beams with different aspect ratio

The objective of the current work is to study the flexural behavior of Concrete-Filled Steel Tube (CFST) composite beams with different aspect ratios. The composite CFST consists of a steel tube filled with Lightweight Concrete (LWC) and a doubly reinforced deck slab of normal concrete. The perfobond shear connector connects the CFST beam and deck slab. Six CFST composite beams were tested; five were filled with LWC, while the sixth hollow beam was used as a control specimen. The main investigated parameters were the effect of the beam aspect ratio (width/depth) and the slab thickness. Three used aspect ratios were (0.4, 0.5, and 0.6). These specimens were compared with the control beam, and three more slabs of variable thickness (75, 85, 100 mm) were used to investigate the effect of slab thickness on the behavior of composite beam. The slabs were doubly reinforced with conventional reinforcement of 6 mm diameter in each direction for all the specimens. Additionally, to investigate the effect of the connector, push out tests are done on three specimens. All specimens were supported and tested using one-point loading. The deflections at midspans and slips produced from the monotonically increased loads were recorded. The results showed that the filled LWC was significantly improved the flexural behavior of the composite beams. On the other hand, the slab with relatively high thickness shows less improvement in composite beam ductility, and this is not surprisingly based on the size effect.