Axial compression behavior of prefabricated T-section thin concrete encased steel short columns

A T-section thin concrete encased steel (T-TCES) column is proposed for the residual buildings, avoiding the convex corners in rooms. The required concrete cover thickness for concrete encased steel members specified in the existing codes is quite large, which is the key problem and to be solved in the proposed column by reducing the concrete covers, facilitating the transportation and installation. To evaluate the mechanical performances of the proposed columns, especially the local stability of the internal T-section steel with the obviously reduced concrete covers, tests of nine short column specimens were conducted under axial monotonic loading. Also, the finite element (FE) analysis was conducted and validated. The effect of the proportion of steel sectional area, concrete strength, stirrup spacing and the concrete encasement thickness outside the flange on the failure modes, load-displacement responses, load-strain responses and characteristic loads were obtained. According to the test and FE analysis results, the peak load can be improve by increasing concrete strength or the proportion of steel sectional area or decreasing the stirrup spacing. The T-TCES columns with low-grade concrete or small stirrup spacing or high proportion of steel sectional area have a better composite action between the internal steel and concrete. Increasing the thickness of the concrete encasement outside the flange can prevent the T-TCES column from cracking. The concrete encasement and reinforcement bars can restrain the internal steel buckling, and improve the steel strength of the composite column compared with the steel column. The calculation methods for the peak and design resistances of the T-TCES column were proposed and proved to show satisfactory accuracy. The simplified model of the load- displacement responses and the calculation methods of the axial stiffness are proposed and validated against the test results.