Characteristics of fire exposure - with particular reference to steel structures

The following presentation specifies the thermal characteristics of the compartment fire exposure and the standard fire exposure as a basis for an analytical fire design of load bearing structures, particularly steel structures. The connection between the two types of exposure is dealt with according to the concept of equivalent time of fire exposure. given in an approximate as well as in a more accurate form. The document was drafted for and included as Chapter 11 and Appendix A in the "Design Manual on the European Recommendations for the Fire Safety of Steel Structures", Publication No 35 of the European Convention for Construction Steelwork (ECCS), Brussels 1985. The Design Manual was prepared within ECCS Technical Committee 3 by a drafting group with the following membership: J. Witteveen, chairman; L. Twilt, secretary; S. Bryl; J.P. Favre. J. Kruppa, M. Law and O. Pettersson

Requirements of Fire Resistance Based on Actual Fires (Swedish Approach)

A rational, analytical approach to a fire engineering design of load bearing steel structures is described. The method of design is directly based on the natural compartment fire concept and on strictly defined functional requirements and performance criteria. The method is permitted to be generally applied in Sweden, as one a1ternative;since more than ten years. For facilitating the practical application, a comprehensive design basis has been worked out in the form of diagrams and tables for a direct determination of the maximum steel temperature during the relevant compartment fire and the corresponding design load bearing capacity of the fire exposed structure. The design basis is presented in a manual which has been given type approval for practical use by the National Swedish Board of Physical Planning and Building. The design procedure has recently been further developed in order to arrive at a design method in regard to fire exposure which is in principal agreement with modern loading and safety philosophy for the non-fire state

Structural fire behaviour - development trends

During the last two decades, a rapid progress has been made in the development of analytical methods for a fire engineering design of load bearing and separating structures and structural members. Consequently, more and more countries are now permitting a classification of structural members with respect to fire to be formulated analytically as an alternative to the internationally prevalent method of classification based on results of standard fire resistance tests. In a long-term perspective, the development goes towards an analytical design, directly based on a natural fire exposure, specified with regard to the combustion characteristics of the fire load and the geometrical, ventilation and thermal properties of the fire compartment. Parallel to this progress, a further development is going on towards a reliability based structural fire engineering design. The development includes contributions related to a practical design format calculation, based on partial safety factors, as well as to an evaluation, based on first order reliability methods. The paper describes and comments on these developments

The role of the university in fire science

Historically , the fire safety code systems now in force had to be written without actually stating their objective level of safety and, still far less , without any analytical measurement of the objectives involved. For this reason, there is an urgent need for future attempts to evaluate the levels of safety inherent in present local and national fire protection regulations. Lack of knowledge with respect to analytical models describing the physical processes of design components and systems has for a long time effectively prevented efforts to quantitatively assess risk levels. As a result of the powerfully increased extent of the international fire research, more and more components and systems are now becoming amenable to analytical and computer modelling

Practical need of scientific material models for structural fire design - general review

More and more countries are now permitting a classification of structural elements with respect to fire exposure to be formulated analytically as an alternative to the internationally preualent method of classification, based on results of standard fire resistance tests. In some countries, the authorities also have taken the next step to approve a general practical application of a direct analytical design procedure, based on the natural compartment fire concept. The process of an analytical structural fire design comprises three main components - the determination of the fire exposure, the thermal analysis and the mechanical behaviour analysis. The components require access to welldefined input information on: (a) material properties for describing the characteristics of the fire load and the compartment fire; (b) material properties for determining the transient temperature state of the fire exposed structure; and (c) material properties for determining the related mechanical behaviour and load-bearing capacity. With a summary presentation of the deuelopment and characteristics of the analytical structural fire design as a background, the paper is focusing on the mechanical material properties at elevated temperatures. A systematic scheme of classification of available tests is referred to and the importance is stressed of using such functionally well-defined tests which give material properties, stringently connected to material behaviour models being independent of the type of load-bearing structure