Numerical studies on the shear behaviour of partially concrete filled steel tubular beams

Partially concrete-filled steel tubular (PCFST) beams are a modified version of concrete-filled steel tubular (CFST) beams, where the concrete filling in the tension zone is optimised while still maintaining the structural integrity of the beam. Research on PCFST has primarily focused on their flexural behaviour, yet there remains a scarcity of understanding their shear behaviour. This paper aims to address this gap by numerically investigating the shear behaviour of PCFST beams and compare it with the shear behaviour of CFST. A finite element model is developed using the ABAQUS software and the main parameters varied in the present paper are shear span-to-depth ratio, concrete compressive strength, steel yield strength, and depth-to-thickness ratio of the steel tube. From the parametric study, it is observed that the influence of concrete compressive strength on the shear behaviour of PCFST beams is not significant compared to the steel yield strength. Additionally, specimens with a shear span-to-depth ratio of less than 0.5 exhibited shear failure which is similar to a CFST beam. To check the applicability of the plastic moment resistance for a PCFST cross-section in a high shear condition, a limiting shear demand-to-capacity ratio is proposed. Furthermore, the shear force obtained from the numerical study is compared with the existing code specifications. The code predictions are found to be very conservative for specimens that had a shear-predominant failure. This is because these codes do not consider the enhancement in the concrete shear strength and the composite action between the steel tube and concrete infill.