Experimental and numerical investigation on exposed RCFST column-base Joint

This paper investigates the seismic performance of exposed RCFST column--base joints, in which the high--strength steel bars (USD 685) are set through the column and reinforced concrete foundation without any base plate and anchor bolts. Three specimens with different axial force ratios (n = 0, 0.25, and 0.5) were tested under cyclic loadings. Finite element analysis (FEA) models were validated in the basic indexes and failure mode. The hysteresis behavior of the exposed RCFST column-base joints was studied by the parametrical analysis including six parameters: width of column (D), width--thickness ratio (D/t), axial force ratio (n), shear--span ratio (L/D), steel tube strength (fy) and concrete strength (fc). The bending moment of the exposed RCFST column--base joint increased with D, fy and fc. But the D/t and L/D play a little effect on the bending capacity of the new column--base joint. Finally, the calculation formula is proposed to assess the bending moment capacities, and the accuracy and stability of the formula are verified.