A simplified method for calculating non-uniform temperature distributions in thin-walled steel members protected by intumescent coatings under localized fires

摘要

This paper presents a method to calculate the non-uniform temperature field of steel members protected by intumescent coatings under localized fires. In this proposed method, the steel member is divided into a number of segments along the length according to the localized fire temperature field, and each segment divided into plate elements with different surrounding fire temperatures. The temperature of each plate element is assumed uniform and is calculated by the lumped mass equation with the thermal conductivity of intumescent coatings approximated using a three-stage thermal conductivity model. Heat conduction between different steel plate elements is ignored. Comparisons of steel temperature results between measured results and the proposed simplified temperature calculation method show very good agreement in temperature distributions along the steel member length, in the cross-section and detailed temperature-time relations at critical and high temperature locations, with differences in calculated and measured average temperatures in different segments being less than 7.2 %. Comparisons of load carrying capacities of axially-loaded steel members using measured temperature distributions and calculated temperature distributions show small (6%) differences.