Abstract：To study the working mechanism of square steel-reinforced concrete-filled steel tubular (SRCFST) members under combined compression-bending-shear loads, a total of 10 square SRCFST specimens were tested. The influence laws of shear-span ratio, axial compression ratio and profiled steel section form on the horizontal capacity and failure modes of specimens were considered. The finite element analysis (FEA) model was established to simulate the testing results and employed to analyze the mechanical behaviors of typical specimen and subsequently the effects of various factors on the horizontal capacity were evaluated. The results showed that the SRCFST members exhibited good ductility, obvious buckling deformation appeared at the compressive side of the steel tube, and the combined effect between the profiled steel and core concrete was found. With the loading directions varying from strong axis to weak axis, an average decrease of 13% on the horizontal capacity of specimens was observed. After setting the stiffeners, the horizontal capacity of specimens increased with an average rate of 21%. During the loading process, the axial load redistributed, and most horizontal and axial loads were carried by the concrete. The interaction force between the profiled steel and the concrete was uneven, and a stronger interaction between the flange of profiled steel and the concrete occurred at the compression zone. Keeping the axial compression ratio constant, when the shear-span ratio was below 0.8, the horizontal capacity of specimens was significantly enhanced as the shear-span ratio decreased. When the axial compression ratio was less than 0.4, the horizontal capacity of SRCFST specimens was improved due to the existence of axial force.
