Experimental and numerical research on hysteretic behavior of CFST frame with diaphragm-through connections

The hysteretic behavior of CFST frame with diaphragm-through connections was investigated experimentally and numerically in this paper. Three frame specimens were designed and tested under reserved cyclic load. The steel tube in the panel zone were weakened by declining the thickness of two specimens. Variable failure modes were observed during the test such as concave of web in the panel zone, convex of flange of column bottom, and weld fracture at the stress-concentrated location. Based on the experimentally-validated FE models, parametric analysis was carried out focusing on the thickness of steel tube in panel zone, axial compression ratio n, the addition of concrete, the thickness of diaphragm-through, the section area of column and the grade of concrete strength. The numerical results reflected that for frames with weak-designed panel zone, the thickness of steel tube in panel zone made a great contribution to the load-carrying capacity and initial stiffness, specifically, while for frames with a balanced or strong-designed panel zone, the variation of the thickness of the steel tube had limited influence, adding the concrete merely into the panel zone could strengthen the panel zone and avoid the shear failure of the panel zone. When the thickness was lower than 8 mm, the load-carrying capacity would sharply decline.