Steel plates are integral components of steel members, particularly vulnerable to local buckling when exposed to fire and subjected to compression or bending loading conditions. These plates, combined with various boundary conditions at different edges, form complete steel sections. This study proposes a behavior and design formulation to determine the ultimate strength of a steel section or member by examining the most vulnerable element with idealized boundary conditions on all edges. Experimental and numerical results from previous studies on whole steel sections were compared and found to align well with this new design approach, proving it simple and effective in determining the behavior and strength of the entire member under elevated temperatures. Using the commercially available finite element software ABAQUS, a numerical investigation was conducted to analyze the compressive and flexural behavior of internal and outstand steel elements, with and without central cutouts, across different plate slenderness and temperature ranges. The reliability and accuracy of the proposed formulation were assessed by comparing it with existing European design standards (EN-1993-1-2) and North American design standards (AISC-360-16) for steel structures in fire exposure scenarios.