Temperature Attained in Intumescent Coating–Protected Concrete-Filled Circular Steel Tubular Sections under the Standard Fire Condition

Abstract

This paper presents the results of an experimental and numerical investigation to obtain a simplified analytical method to calculate intumescent coating thermal conductivity and temperatures of intumescent coating–protected concrete-filled circular steel tubular sections by using an equivalent section factor for the steel section without concrete infill. An important test of correctness of the equivalent steel section factor is that when the resulting thermal conductivity of the intumescent coatings is used in numerical modeling of concrete-filled sections, the steel and concrete core temperatures can be accurately calculated. This paper first reports the experimental results of 32 fire tests conducted on intumescent coating–protected concrete-filled circular sections; experimental variables included coating thickness and circular section dimensions. The fire test results are then used to assess the the accuracy of two existing methods of calculating the equivalent steel section factor. These methods were shown to give a wide range of effective thermal conductivity–temperature relationships for the same intumescent coating and not being able to accurately predict the steel and concrete core temperatures consistently. This paper then proposes a new equation to calculate the equivalent steel section factor, which is demonstrated to be able to more accurately predict the temperatures of intumescent coating–protected concrete-filled steel sections.