Finite element investigation of circular rubberized CFST beams under Four-Point loading

This paper presents the nonlinear finite element (FE) analysis of circular concrete-filled steel tubes (CFST) with rubberized infill concrete (RuC) under flexure. The FE models were first developed and validated against the existing experimental test results of the CFST beams with normal concrete (NC) and RuC (15% and 30% rubber replacement). Good agreement between the numerical and experimental results was obtained. The validated models were then used to perform parametric studies of forty-five specimens to examine the effect of parameters such as tube diameter, tube thickness, steel yield strength, loading distance, span length, and rubber replacement ratio on the CFST beams under four-point bending. Steel tube properties have a direct influence on the beam moment capacity, whereas loading distance and span length have negligible effects on the ultimate capacity. With 30%RuC, ductility improved significantly, but a lower capacity of up to 14% reduction was found compared to CFST beams with NC. A comparison of the initial flexural stiffness of the numerical results with four design codes showed that AIJ and BS5400 gave more accurate predictions compared to EC4 and AISC.