Experimental Flexural Performance of CFST Beams with Longitudinal Steel Plate Reinforcements

The conventional Concrete-Filled Steel Tube (CFST) member, like any other structural member, requires strengthening to further enhance its structural properties. This research is presented with the intention to delay the occurrence of tensile concrete cracking and improve the bending stiffness, which in return allows the conventional CFST member to attain higher strength capacities. Therefore, a feasible yet practical method is introduced by utilising longitudinal steel plate reinforcements along the inner beam’s section, particularly along the tensile region of the concrete core. This method positively affect the strength capacity of CFST columns tested under compression, hence the flexural strength of beam is to be uncovered in this research. The steel plates employed vary in terms of quantity (1,2,3), height (30, 60, 90 mm), and thickness (1.5, 3.0, 4.5 mm). An experimental investigation is performed on eight rectangular CFST beams tested under pure bending. Minimal welding is required, in which the steel plates are spot welded only at each end of the inner beam’s section. Test outcomes revealed the significant enhancement pertaining to the flexural performance specifically the moment capacities and bending stiffness of the strengthened CFST beams. An improvement of 43% is achieved by the CFST beam, utilising up to three steel plates. Furthermore, the steel plates work effectively in improving the tensile region of the concrete core, as reflected by the improved flexural behaviour response. Additionally, a theoretical investigation is introduced by proposing the plastic stress distribution model for the ultimate moment predictions. The theoretical outcomes successfully verified the experimental results by 95% with a standard deviation of 0.03. The findings are plausible and in good agreement with the experimental outcomes, hence can be used to predict the ultimate moment capacities for CFST beams reinforced with varying steel plates parameters