Probabilistic Evaluation of Structural Fire Resistance

The work described herein seeks to investigate a probabilistic framework to evaluate the fire resistance of structures given uncertainty in the fire load and structural resistance parameters. The methodology involves (i) the identification and characterization of uncertain parameters in the system, (ii) a stochastic analysis of the thermo-mechanical response of the structure, and (iii) the evaluation of structural reliability based on a suitable limit state function. The methodology is demonstrated through the analysis of a protected steel beam using Monte Carlo simulation with embedded finite element simulations. Model dimensionality is reduced using a response sensitivity analysis, and limit state functions are defined based on limiting deflection criteria used in fire resistance tests. Results demonstrate that the 1-h rated beam resists a natural fire exposure with a failure probability of less than ten percent, although additional discussion is warranted regarding what might be considered an acceptable level of risk in structural fire design. The study also demonstrates that probabilistic analysis of structural fire resistance provides an enhanced understanding of the factors affecting the resistance of structures to fire and offers a means for rationally improving structural designs to meet target performance objectives.