Post-fire integrity of composite gratings for offshore platforms

The post-fire integrity of pultruded phenolic/glass and polyester/glass floor gratings, of the type used offshore and elsewhere, was investigated. The aim was to determine whether glass/phenolic gratings may be safely walked on, post-fire, by offshore workers and fire-fighting teams. The load to be resisted was identified as equivalent to a running person carrying a load, the combined mass being 150 kg. The maximum resulting dynamic strains were determined by strain gauges on the undersides of the individual beam elements of gratings. This enabled target values of post-fire bending resistance to be identified. Individual beam elements from the gratings were exposed to heat fluxes of 12.5, 37.5 and 100 kW/m² using a propane burner, for periods up to 16 min, after which the residual strength was measured. Phenolic gratings showed longer ignition times, with lower flame and smoke emission, as well as greater post-fire strength compared to polyester ones. At the lowest flux, 12.5 kW/m², all gratings remained serviceable beyond 16 min. At higher heat fluxes, the phenolic gratings retained some post-fire strength, assisted by the formation of a carbonaceous char binding the fibres. However, this was somewhat below the target level. A study of the effect of testing speed indicated that fire-exposed gratings are not especially strain-rate sensitive.