Effects of Gap Arrangement on the Compression Behavior of Square Tubed Steel Reinforced-Concrete Columns

For a tubed concrete column, generally, the tube gaps are arranged at column ends to avoid the steel tube carrying loads directly. This paper experimentally and numerically investigated the behavior of square tubed steel reinforced concrete (TSRC) columns with an additional gap at the mid-height of the steel tube. Four square intermediate TSRC columns were tested under axial and eccentric compression, and the main test parameters were the load eccentricity ratio and width-to-thickness ratio of steel tube. The failure modes and ultimate strength were analyzed. The test results demonstrated that the columns with two types of gap arrangement schemes showed similar failure modes. The axial compression strength of the column with an additional gap at mid-height was slightly higher than that of the column with gaps at the column ends, while the eccentric compression strength of column showed the opposite result. A detailed finite element (FE) model was developed and verified, in which the material nonlinearity and initial geometric imperfection were considered. Further parametric analysis was carried out based on the verified FE model.