Design Formulation for Critical Buckling Stress of Steel Columns Subjected to Nonuniform Fire Loads

Assessing the stability of steel building frames exposed to fire conditions is challenging due to the need to consider elevated temperature properties of steel, nonuniform heating of structural members, and large deformational demands on the frames. There has been significant progress recently in simulating the response of structural members and systems under fire loads using finite element methods. There is a need, however, for conducting additional analysis while expanding upon previous work to allow for the development of additional design provisions for column buckling while accommodating varying temperature profiles. This study introduces a framework for conducting stability analyses of W-shape steel columns subjected to demands imposed by fire loads considering nonuniform longitudinal temperature profiles. Results from the analyses show good agreement with available strength design equations of steel columns at ambient and elevated temperatures. An equation is proposed to compute the Euler elastic buckling stress in case of nonuniform longitudinal distribution of temperature. In addition, another equation is proposed to calculate the critical buckling stress of steel columns subjected to nonuniform longitudinal temperature demands. The efficiency of the proposed equations is investigated when two additional nonuniform longitudinal temperature profiles are considered.