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Thermal performance of composite slabs with profiled steel decking exposed to fire effects

Published

Author(s)

Jian Jiang, Joseph Main, Jonathan Weigand, Fahim H. Sadek

Abstract

This paper presents detailed numerical modeling of heat transfer in composite floor slabs with profiled steel decking. The detailed modeling approach represents the concrete slab with solid elements and the steel decking with shell elements. After validating against experimental data, the detailed model is used to conduct a parametric study to investigate the influence of thermal boundary conditions, thermal properties of concrete, and slab geometry on the temperature distribution within composite slabs. The results show that the fire resistance of composite slabs, according to the thermal insulation criterion in Eurocode, is governed by the maximum temperature occurring at the unexposed surface of the slab, rather than the average temperature. The emissivity of steel has a significant influence on the temperature distribution in composite slabs. A new temperature-dependent emissivity is proposed for the steel decking to give a better prediction of temperatures in the slab. The ASCE models of concrete conductivity are quite similar to the upper limit in EC4, which is recommended for the numerical analysis. A constant specific heat value of 1000 J/(kg·K) is recommended for simple analytical calculations. The moisture content of the concrete has a significant influence on the temperature distribution, with an increment of 1 % in moisture content leading to an increase in the fire resistance of about 5 minutes. The height of the upper continuous portion of the slab is found to be the key geometrical factor influencing heat transfer through the slab, particularly for the thin portion of the slab. Heat transfer through the thick portion of the slab is also significantly affected by the height of the rib and the width at the top of the rib.
Citation
Fire Safety Journal
Volume
95

Keywords

composite slab, heat transfer analysis, finite element detailed model, thermal boundary, thermal property, slab geometry

Citation

Jiang, J. , Main, J. , Weigand, J. and Sadek, F. (2018), Thermal performance of composite slabs with profiled steel decking exposed to fire effects, Fire Safety Journal, [online], https://doi.org/10.1016/j.firesaf.2017.10.003, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=923515 (Accessed December 1, 2021)
Created February 4, 2018, Updated October 12, 2021