Introduction of a paper about experimental investigations on
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More recently, Keller et al. [23,24] reported results of fire resistance tests on 195 mm thick GFRP pultruded cellular panels, made of E-glass fibres and non-fire retarded isopthalic polyester resin. The 2.75 m span slab was subjected to the service load and,simultaneously, its bottom surface was exposed to the ISO 834 fire.The slab was able to resist fire exposure from the underside for 57 min: structural collapse was not caused by tensile failure in
the damaged hot face; instead, an instability induced failure mechanism occurred on the cold compression flange, due to the loss of lateral support of the fibres following resin softening.
More recent investigations carried out by Bai and Keller [25] explain that failure may have been triggered by exceeding the shear strength at the web–flange junctions. In order to improve the fire resistance of the GFRP panels, the authors protected the bottom flange of the panels with a water cooling system, developing an original concept used to protect steel elements, also successfully applied by Davies and Dewhurst in glass–epoxy pipes [26]. By using relatively modest flow rates (applicable in real buildings), it was possible to maintain the structural integrity of the GFRP panels after 120 min of exposure.
Presently, the commercially available resins and flame retardants allow fulfilling most flammability requirements. However, if changing the matrix formulation allows overcoming fire reaction restrictions, in terms of fire resistance, this approach does not achieve the fire endurances typically required for primary structural elements (60–90 min). Within the literature survey, internal water cooling proved to be the most effective solution, being, in addition, a very well material-adapted solution.
However, internal water cooling is only applicable to tubular shapes, such as cellulartype slab panels and, therefore, other structural shapes still require alternative and effective fire protection solutions. The use of intumescent
coatings has proved to improve the fire reaction [27,28] and post-fire properties of FRP materials [27,29]. However, limited research was performed regarding the fire resistance of FRP structural elements under loading. With regard to the use of thick layers (such as those made of spray applied materials or boarding systems) for the fire protection of FRP materials under loading, to the authors’ best knowledge no research has been reported and,
although this solution may lack material-adaptability (due to the non-negligible increase of self-weight), high fire ratings are foreseen.
This paper presents results of experimental investigations on the behaviour of loaded GFRP pultruded fiberglass profiles when submitted to fire. The main objective was to study the viability of their use in floors of building, as structural elements, taking into account the fulfilment of fire resistance requirements. The feasibility and efficacy of using different protective coatings/layers, which are often used to protect structural steel, to provide fire protection to
GFRP pultruded profiles was investigated and compared to a water cooling fire protection system. Dynamic mechanical analyses (DMA) and differential scanning calorimetry (DSC) and thermogravimetric (DSC/TGA) measurements were first performed in the GFRP material and also in the fire protection materials in order to determine their thermo-physical and thermo-mechanical properties.
Subsequently, fire resistance tests were conducted on an oven to investigate the behaviour of loaded GFRP pultruded beams (unprotected and protected) in a fire situation, simulated according to the ISO 834 time–temperature curve. These tests investigated: (i) the feasibility of using the investigated passive fire protection systems; (ii) the thermal response of the GFRP material when exposed to fire; (iii) the mechanical response and failure modes
of the beams under a simulated fire; and (iv) the fire resistance.
