EVALUATION OF ULTIMATE STRENGTH OF SQUARE HOLLOW SECTION UNDER ELEVATED TEMPERATURES WITH VARYING SLENDERNESS RATIOS AND WIDTH-TO-THICKNESS RATIOS

Detailed FEM models employing shell elements were developed to evaluate the ultimate strength of square hollow steel columns with varying slenderness ratios and width-to-thickness ratios under elevated temperatures. The analyses considered plasticity, flexural buckling, and local buckling of the columns. It was quantitatively demonstrated that even columns with relatively small width-to-thickness ratios undergo local buckling at high temperatures. Furthermore, by focusing on fiber stresses in the column cross-section, the ultimate axial strength was evaluated using the tangent modulus theory. In addition, the ultimate strength under combined axial force and uniform bending at elevated temperatures was assessed.