ISO/TC 92/SC 4/WG 12 - Structures in fires

This document provides a methodology for assessing the performance of structures in the built environment when exposed to a real fire. This document, which follows the principles outlined in ISO 23932-1, provides a performance-based methodology for engineers to assess the level of fire safety of new or existing structures. NOTE The fire safety of structures is evaluated through an engineering approach based on the quantification of the behaviour of a structure for the purpose of meeting fire safety objectives and can cover the entire time history of a real fire (including the cooling phase), and its consequences related to fire safety objectives such as life safety, property protection and/or environmental protection.

ISO/TR 24679-6:2017 provides an example of fire safety engineering design in the application of ISO 24679‑1 to an office building. In ISO/TR 24679-6:2017, an overall structural analysis of a building is undertaken. It consists in a numerical assessment of the structural performance of an eight-storey concrete building when subjected to a fire. This analysis is performed in order to demonstrate that the fire safety objectives, for the relevant design fire scenarios, due to structural behaviour of building in the event of fire, are met with the trial plan for the safety of structure. With regards to this, a fully developed fire was studied. The purpose of this document is to assess the performance of an office building which is fully accessible to public in case of fire, using ISO 24679‑1. In this respect, a critical design fire was identified and analysed using detailed fire modelling. A more detailed analysis was then performed for critical design fire using the finite element model. The advanced model provided all the comprehensive information necessary for analysing the given built environment with respect to fire safety. It is to be noted that this document only addresses the fire safety objectives related to the structural performance during fire. The analysis within this document is therefore only part of the overall building fire safety strategy.

ISO/TR 24679-4:2017 provides a fire engineering application relative to the fire resistance assessment of a fifteen-storey steel framed building following the methodology given in ISO 24679-1. This document describes the adopted process which follows the same step by step procedure as that provided in ISO 24679-1. The annexes of this document present the detailed assessment results obtained for the most severe fire scenarios on the basis of the outcome of this specific fire safety engineering procedure for the building. The fire safety engineering applied in this example to the office building with respect to its fire resistance considers specific design fire scenarios as well as the corresponding fire development. It takes into account fully-developed compartment fires. In realistic situations, activation of fire suppression systems and/or intervention of fire brigade are expected, but their beneficial effects are not taken into account. It should be noted that these severe fire scenarios have been selected for fire resistance purposes. Global structural behaviour is not explicitly considered, but implicitly included in the calculation formulae. Since the building of the example is located in a seismic region, principal structural elements are rigidly connected to each other. Load redistribution from heated elements to cold surrounding elements exists, but it's not taken into account in the design calculations. By this approach, design is conservative, while the process of safety checking is greatly simplified and clear. As a result, all the calculations were carried out by explicit algebraic formulae.

ISO/TR 24672-2:2017 provides a fire engineering application relative to fire resistance assessment of an airport terminal structure according to the methodology given in ISO 24679‑1. It follows step by step the procedure given by ISO 24679‑1. Some requirements relative to Chinese building regulation are taken into account concerning the fire scenarios. The fire safety engineering applied to an airport terminal takes into account the real fire data based in fire tests. It is important to note that the intervention of fire service brigade dedicated to this airport, located approximately 1 km away, has been taken into account in definition of fire scenarios. For the fire modelling, both fire extinguishing system and the smoke extraction are not considered but the fire fighter intervention has been taken into account 10 min after the starting of fire.

ISO/TR 24679-4:2015 provides a fire safety engineering application relative to fire resistance assessment of an open car park according to the methodology given in ISO/TS 24679. It describes the adopted process which followed the same step by step procedure as that given within ISO/TS 24679. The annexes of ISO/TR 24679-4:2015 presents the detailed numerical analysis results obtained for most severe fire scenarios on the basis of this specific fire safety engineering procedure for open car parks.

ISO/TS 24679:2010 provides a methodology for assessing the performance of structures in the built environment when exposed to a real fire. ISO/TS 24679:2010, which follows the principles outlined in ISO 23932, provides a performance-based methodology for engineers to assess the level of fire safety of new or existing structures.