Cyclic behavior of circular TSRC column to steel beam frames

Tubed steel reinforced concrete (TSRC), as a new-type composite member, has drawn increasing interest in recent years due to its appropriate mechanical properties. However, studies on such structural form have mainly focused on the columns and joints, with very limited investigations made on the structural system, resulting in an insufficient design basis. To make up this research gap, this study investigated first the cyclic behavior of circular tubed steel reinforced concrete (CTSRC) column to steel beam frames. Two half-scaled double-bay two-story CTSRC column to steel beam frames were designed and tested under quasi-static loading, where the column-beam strength ratio (η) was considered as the main parameter. The test results indicate that the frame with higher η of 2.5 fails in beam plastic hinge (PH) mechanism; while that with the lower η of 0.7 fails in column PH mechanism. Due to the good cyclic behavior of CTSRC columns, the deformation capacity of the frame failed in column PH mechanism does not decrease significantly. A 3D finite element model (FEM) using the software ABAQUS was developed and validated with the test results. The parametric study indicates that the axial load ratio, column-beam strength ratio, and beam-column stiffness ratio are the primary factors affecting the load-deformation relation of CTSRC frames. Floor slabs were also analyzed using the FEM and it was found that the effect of slabs on the behavior of CTSRC frames was similar to the increase of steel beam strength and stiffness.