Fire performance of steel elements protected with ICs and subjected to large tensile deformations

Steel elements may be subjected to large deformations during a fire or as a consequence of previous accidental event that triggered the fire, such as an earthquake or an explosion. In such cases, fire protective intumescent coatings (IC) applied on the steel elements can crack or detach as a result of the large deformation and undergo earlier fall-off of the protection during fire exposure. Such issues are known to depend, among other factors, on the type and thickness of the IC, as well as the geometry and layout of the steel profiles. However, there is at present very little knowledge on the entity of tolerated deformations or of possibly reduced performance of damaged ICs during fire. This project was aimed at advancing such knowledge by means of an experimental campaign, where four different types of ICS (one water-based, one solvent-based two epoxy-based) were applied on 39 steel plate samples, which were first subjected to different tensile strains and then tested in an electric furnace under constant heating rate up to achievement of the design temperature in the steel. The damage of the IC before and after the furnace tests was evaluated and the performance of the strained samples during fire exposure were evaluated against the performance of unstrained reference samples. The results show that, while the two water- and solvent-based ICs could tolerate quite large tensile strains (up to 16%) without significant damage nor reduction of the performance in fire, the two epoxy-based ICs showed large cracks and detachments when subjected to tensile strain larger than 5-8% and were not able to provide the required fire protection to the steel samples during fire.