Steel-concrete-steel composite beams with thin perfobond connectors and C-ties: Flexural performance

The flexural performance of steel-concrete-steel (SCS) sandwich composite beams utilising thin perfobond connectors and C-ties (PBL-CTs) was investigated in this paper. Four-point bending tests were conducted on six SCS beams to explore the effects of C-ties, steel plate thickness, top steel plates, and shear-span ratio on their flexural performance. The load-deflection behaviour of the SCS beams was categorized into three distinct stages: elastic, yielding, and recession stages. During the yielding stage, C-ties functioned similarly to stirrups in reinforced concrete (RC) beams, restricting the propagation of diagonal cracks and enabling SCS beams to sustain the load, transitioning from shear failure to flexural failure and thus enhancing the ductility of the beams. Additionally, the top steel plates provided confinement to the concrete in the compression zone, and their premature local buckling led to the compression collapse of the concrete and the premature failure of the specimen, resulting in a shorter yield plateau and poorer ductility. Diagonal cracks resulted in a nonlinear distribution of relative slip between the bottom steel plates and the concrete in the shear-span region. According to the load-slip curves from the push-out experiments, the steel-concrete interface was full shear connection. Finally, considering the shear lag effect of the outer steel faceplates and employing an effective width method, a series of prediction formulas for the flexural performance of SCS sandwich composite beams were proposed and proved to be accurate by comparison with experimental results.