Fire performance of single-storey steel structures - case study: Industrial hall and retail building

Steel structures must be designed for adequate performance in case of fire. This study aims to compare fire design methodologies for portal frame structures based on a prescriptive approach against a performance-based approach relying on the natural fire models recently incorporated into the Eurocodes. The focus is on portal frame structures representative of industrial halls and retail buildings, which are characterized by large open spaces where flashover is unlikely to occur. The prescriptive design approach assesses structural response under the ISO 834 standard fire curve, which does not represent a real fire in these large open-plan spaces. Conversely, the performance-based design approach incorporates natural fire models developed to reflect more realistic fire scenarios given the characteristics of the structure under study, such as localised fires. The new generation of Eurocode 1 Part 1–2 introduces various localised fire models for structural components, considering their positions relative to flame exposure. This study employs localised fire models to assess the thermal-structural performance of the portal frame structures. Results indicate that unprotected steel structures do not meet the required fire resistance classifications under the prescriptive design approaches stipulated by the Italian Fire Prevention Code. However, when using physically-based fires within performance-based design approach, the anticipated failure time of the unprotected structures is significantly extended, possibly beyond the requirements depending on the performance objectives. This paper suggests that the application of fire protection materials can be optimized leading to more efficient and cost-effective fire safety designs. • A fire design methodology is proposed for single-storey steel structures. • Prescriptive and performance-based fire design approaches are compared. • Localised fire models in the new generation of Eurocode are introduced in a performance-based design approach. • Rational use of fire protection is determined using realistic fire scenarios and advanced analysis.