Study on the mechanical behavior of L-shaped concrete-filled steel tubular columns under axial compression

In this paper, a total of six different ribbed and two nonribbed L-shaped concrete-filled steel tubular (CFST) short columns are designed; finite element modeling and calculations are carried out and verified with measured results. The optimal ribbing method among the ribbing methods applied is proposed. The mechanisms of the longitudinal stress of the concrete, longitudinal stress of the outer steel tube, and lateral compressive stress of the concrete for the L-shaped CFST short column without ribs and with the optimal ribbing method are compared and analyzed. The results show that the optimal ribbing method involves setting half-width longitudinal stiffening ribs in the middle of the two wide sides of the L-shaped steel tube. The stiffening ribs can delay the occurrence of local buckling failure of the steel tube, thus strengthening the restraining effect of the steel tube on the concrete and improving the uniformity of the longitudinal stress of the core concrete. In addition, based on an analysis of a large number of parameters, four methods for calculating the bearing capacity of nonribbed L-shaped CFST short columns are compared. A design formula for the bearing capacity of ribbed L-shaped CFST columns is proposed by considering the improvement in the concrete performance. The calculation results agree well with the finite element and experimental results, and the error is <5%.