Interpolation Formulas for Coefficients Reducing the Strength of Steel and Aluminum Alloys in Increasing Temperatures

Heating of steel or structural aluminum alloys at a speed of 2 to 50 K/min - characterizing the fire conditions - leads to a reduction in mechanical properties of the analyzed alloys. The limit of proportionality f_p, real f_yand proof f₀₂yield limit, breaking strength f_uand longitudinal limit of elasticity E decrease as the temperature increases. Quantitative evaluation of the thermal conversion in strengths of structural alloys is published in Eurocodes 3 and 9, in the form of dimensionless graphs depicting reduction coefficients and selected (tabulated) discrete values of mechanical properties. The author’s proposal for an analytical formulation of code curves describing thermal reduction of elasticity modulus and strengths of structural alloys recommended for an application in building structures is presented in this paper.