Probabilistic analysis of steel columns protected by intumescent coatings subjected to natural fires

摘要

Probabilistic analysis is needed to yield a rational fire safety design. Intumescent coatings are passive fire protection materials widely used in steel construction. Due to the organic components, intumescent coating has an aging problem. This paper presents a probabilistic analysis of steel columns protected by intumescent coatings subjected to natural fires. Monte Carlo simulations were conducted to investigate the aging effect of intumescent coatings on the reliability of protected steel columns. The study found that aging has an effect of decreasing the reliability index of steel columns protected by intumescent coatings. That decreasing effect increases with increasing aging years. The decrease is more serious for cases with high load ratio, μ_0, than for cases with low μ_0. For the investigated cases with low load ratio (μ_0 ≤ 0.3), the amount of the decrease of reliability index, Δβ, due to the effects of aging is less than 0.2; and for the investigated cases with high load ratio (μ_0 ＞ 0.3), the maximum Δβ is about 0.24. Based on the calculated reliability index, a probability based approach with a design example was given to assess the service life of intumescent coating for steel structures. The approaches given in this paper can also be used for probabilistic analysis of steel columns protected by conventional inert fireproofing materials.