Flexural behaviour of composite rectangular steel beams filled with concrete

In the construction of structures of current world, steel-concrete composite members are considered to be the key components of a structure. Concrete filled steel tube (CFST) is one such composite member which can be used as both flexural as well as compressive member. The advantages of using CFST as structural member are more, first important one is, the increase of load carrying capacity of member due to the confinement of steel and the second one is delay of local buckling of steel tube. In the current study, the flexural behaviour of CFSTs under four point bending load is considered. A total of six CFST specimens were tested as flexural members under four-point loading with loading point considered at different distances from support. Beams of span length 1000 mm, cross-section 50 mm x 50 mm and 2 mm thickness, were tested. Steel sections were filled with grade M30 concrete, cured and tested after 28 days. The failure modes, ultimate load, load versus mid-span deflection of the specimens were studied. The test results indicate that using filled steel sections can provide considerable improvement in load carrying capacity and delay of failure of steel sections.