This paper aims to deal with the experimental and numerical investigations of the fire protection performance of a waterborne intumescent coating (IC) on structural steel in case of natural fires. Based on own small-scale laboratory tests, an advanced numerical model is developed to simulate the fire protection performance of the investigated coating in case of arbitrary fire scenarios. The insulation efficiency of the coating is described within the model by temperature and heating rate-dependent material properties, such as expansion factors, thermal conductivity and heat capacity. The results of the numerical model are compared to own large-scale fire tests of an unloaded I-section beam and column.
As natural fires can show arbitrary regimes, the material properties of the waterborne IC are investigated for various heating rates. Based on these investigations, a material model for the IC is implemented in the finite element program ABAQUS. With the help of user subroutines, the material properties of the coating are introduced for both the heating and cooling phase of natural fires, allowing for two- and three-dimensional thermomechanical analyses of coated steel elements.
The results of the performed small-scale laboratory tests show a heating rate-dependent behavior of the investigated coating. The mass loss as well as the expansion of the coating change with the heating rate. Moreover, the material properties obtained on small scale are valid for large scale. Therefore, a material model could be developed that is suitable to reproduce the results of the large-scale fire tests. Additionally, with the help of the numerical model, a dimensioning approach for the dry film thickness (DFT) of the investigated coating is derived for arbitrary natural fires.
The material properties presented in this paper are only valid for the investigated waterborne IC and the parameter area that was chosen. However, the developed modeling approach for the fire protection performance of ICs is general and can be applied for every coating that is part of the intumescent product family.
Until now, only few research works have been carried out on the fire protection performance of ICs under non-standard fire exposure. This paper deals extensively with the material properties and the material modeling of a waterborne IC exposed to natural fires. Especially, the laboratory examinations and the numerical simulations are unique and allow for new evaluation possibilities of ICs.
The work presented in this paper is part of the German research project “Test procedures for thermal material properties of fire protection claddings and intumescent coatings for the design of steel structures exposed to natural fires” (in German: “Prüfverfahren für thermische Materialkennwerte von Brandschutzbekleidungen und reaktiven Brandschutzsystemen für die Bemessung von Stahltragwerken bei Naturbränden”) (AiF 19176 N). The authors express their deep gratitude for the financial support received from the Federal Ministry for Economic Affairs and Energy.
Weisheim, W., Schaumann, P., Sander, L. and Zehfuß, J. (2019), "Numerical model for the fire protection performance and the design of intumescent coatings on structural steel exposed to natural fires", Journal of Structural Fire Engineering, Vol. 11 No. 1, pp. 33-50. https://doi.org/10.1108/JSFE-01-2019-0004Download as .RIS
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