A practical tool for evaluating fire induced failure probability of steel columns designed based on U.S. prescriptive standards

Previous research has investigated and developed systematic probabilistic models for parameters involved in determining the reliability of a structure under fire. The established models have been summarized and applied in this paper to quantify and compare the reliability of steel columns protected based upon the US prescriptive approach. A set of columns with a range of section factors are selected to study the influence of utilization ratio, restraint conditions, and fuel load density on the probability of failure under fire. The results show a relatively large variation in the value of probability of failure for columns with similar fire protection rating but different section factors and utilization ratio. The influence of fuel load density is presented in the form of fragility functions, where the probabilities of failure for expected fuel load density values are discussed. In addition, the probability of failure for columns across different stories of a building is calculated, leading to the conclusion that further harmonization of safety levels can be achieved if reliability-based quantifications are introduced in the design process.