Numerical Investigation of the Flexural Performance of Slender CFST Beams with Varied Shapes of External Stiffeners

The concrete-filled steel tube (CFST) beams are recommended for adopting in the modern composite structure since it achieves a higher load capacity and ductility behaviour than the conventional structural members. Using CFST beams with slender steel cross-section led to reduce the overall cost of the structures compared to those with compact cross-sections; however, it is more likable to buckle under the compression stress. Therefore, providing external stiffeners along the four sides of CFST beams expected to reduce the overall self-weight also can provide more stiffening to the steel’s section that led to improve the loading capacity. In this study, a finite element (FE) method was adopted for numerically investigated the flexural performance of the square CFST beams stiffened with different shapes of external grooves that provided along the beam’s sides. The FE software named ABAQUS was adopted for this purpose where the original model of CFST beam analysed and verified with the corresponding tested specimen. After that, additional CFST model have been built and analysed to investigate further parameters including the effects of varied tube’s thickness, steel yielding strength, concrete compressive strength and different external grooves shape (V-shaped, U-shaped, C-shaped, double V-shaped). The results established from the numerical analyses showed that the ultimate bending capacity (Mu) of the stiffened CFST models was generally enhanced by increasing their concrete strength, steel yield strength and tube’s thickness but in varied percentages. For example, increasing the tube thickness from 1.5 mm to 3.0 mm achieved an improvement in Mu values of about 72.3\%. while fewer improvement percentages have been recorded of about 11.9\% when only the core concrete strength increased from 25 MPa to 55 MPa. Furthermore, the shape and number of grooves have positive impact on the bending capacity of stiffened CFST models, where using U-shape, C-shape and V-shape external grooves were led to improve the Mu value of about 2.8\%, 10.7\%, and 11.1\%, respectively. Thus, the energy absorption of these models was improved accordingly.