The effect of thermal creep on the fire resistance of steel columns

Abstract

An appropriate assessment of the structural fire resistance of steel columns necessitates an accurate mechanical material modeling considering thermal creep in the stress-strain response of steel at elevated temperatures. This paper presents a novel thermal creep model achieved from available experimental results in the literature and its application to structural members in fire within a numerical study on the proposed creep model. Based on this model, a comparative set of numerical studies is performed for a specific benchmark structure in fire conditions, considering protected and unprotected structural steel columns, different stress ratios, different severity of fire exposure and the role of creep buckling. The effect of thickness of the protection material and associated heating rate of the structure on the fire resistance with regard to creep buckling is also investigated. In addition, the structural buckling behavior in fire conditions with explicit consideration of thermal creep in the aforementioned model is studied in comparison to the existent simplified constitutive material model with implicit creep consideration in EN 1993-1-2 [1] for the benchmark structure. The results of this paper highlight the necessity of including thermal creep in the state-of-the-art advanced structural fire design in engineering practice.