Flexural Behavior of Concrete-Filled Steel Tube Beams Composite with Concrete Slab Deck

Concrete-filled steel tube (CFST) beams have shown their flexural effectiveness in terms of stiffness, strength, and ductility. On the other hand, composite bridge girders demand durable and ductile girders to serve as tension members, while the concrete deck slab resists the compression stresses. In this study, six composite CFST beams with concrete slab decks with a span of 170 cm were investigated under a four-point bending test. The main variables of the study were the compressive strength of the concrete deck, the size of CFST beams, and the composite mechanism between the CFST girder and the concrete deck. The results showed that the flexural strength and ductility of the composite system increased by 20% with increasing concrete compressive strength. The study revealed that the higher-strength concrete slab deck enabled the CFST beam to exhibit improved flexural behavior with reduced deflections and enhanced resistance to cracking. The findings also highlighted the importance of considering the interactions between the steel tube and concrete slab deck in determining the flexural behavior of the composite system revealed by strain distribution along the composite beam profile as determined using the digital image correlation DIC technique, where a 40% increase in the flexural strength was obtained when a channel section was added to the joint of the composite section.