Heat Transfer in Steel Structures and Their Fire Resistance

Abstract

This chapter deals with the fire resistance of composite beams with unfilled voids and temperature modeling with fire flux data and intumescent coating. The chapter quantitatively predicts the amount of additional protection required when the voids between the top flange and the underside of the steel deck are unfilled. Two fire tests are carried out on a conventional I-beam floor structure with the same 18-mm board protection, but one with filled voids and the other with unfilled voids. Moment resistance calculations involve dividing the beam into four elements, the top flange, the upper half of the web, the lower half of the web, and the bottom flange, and considering the slab as one single element. The strengths of these elements depend on their temperatures at different times during fire tests. The temperature development in a steel section during fire is calculated with a heat transfer and thermal conduction model, TFIRE, developed at The Steel Construction Institute. The steel section temperatures are calculated with the data of heat flux into the steel measured in a fire test, instead of the fire temperature. The chapter also discusses the behavior of intumescent coating under fire. The heat conductivity value of intumescent coatings is modeled, based on fire test data.