Behavior of Hollow-Core Steel-Concrete-Steel Columns Subjected to Torsion Loading

The torsional behavior of hollow-core steel-concrete-steel (HC-SCS) columns is presented using finite-element (FE) and analytical approaches. The HC-SCS columns consist of a concrete shell sandwiched between two steel tubes. Software was used to develop a three-dimensional model of an HC-SCS column that was subjected to torsional loading. The FE results were validated against the experimental results collected from six HC-SCS columns tested under pure torsion. The average error from the FE analysis was 4.8%, compared with experimental results, when predicting the column's torsion strength. The study revealed that the interaction between the steel tube's stiffness and concrete shell's thickness controls the behavior of the column. A parametric study was conducted to further analyze each parameter affecting the column's torsion behavior. The parametric analysis concluded that the torsional behavior of the column mainly depends on the outer steel tube's properties and the thickness of the concrete shell. A simplified equation was developed to predict the torsion strength of the member using a direct method of stress analysis. The proposed equation predicted the members' torsion strength with an accuracy greater than 90%. (C) 2016 American Society of Civil Engineers.