International Organization for Standardization (ISO)
Status
Latest
ISO/TR 12470:1998
Scope
Direct and extended applications of test results are the two possible ways to ensure that a modified element will have a good possibility of obtaining the same fire rating as that of the original tested specimen. In both cases these applications refer only to the fire rating that the building element can expect to reach if it were to be tested in a furnace according to the standard fire used for the reference test.
For each type of element of construction, the application of test results will be considered under two sub-headings.
a) Direct application: this section identifies the modifications that can be made to the design of the tested element without reducing its fire rating. These possible modifications are based on obvious knowledge and do not need further evaluation. In every case it is, at least, assumed that the basic materials used for the tested sample will not be changed. The results obtained from tests performed using standard configurations are valid for the field of application derived from that configuration, regardless of any specific advice given in the following chapters.
b) Extended application: this will require in every case an assessment by a fire expert either in developing rules of application or evaluating the results of fire engineering calculations or making a judgement. In every case it will be taken into consideration that extended application may take into account the difference between the result of the original test and the fire resistance required for the untested element.
A judgement is the result of a qualitative process, normally carried out by experts. Judgements are used to justify a change of design or method of construction which may use, for example, empirical data derived from tests, established physical properties, hot and cold state calculations, a knowledge of fire exposure, fire behaviour and response of the construction, either in isolation or in combination.
1) Rules of application: these would be applied universally even by persons without expertise in fire as part of the "field of application" of the test result for a given family of products. These rules may require cold state calculation. The quantification of these rules would be agreed universally based upon validated experience related to generic constructions or components. This could cover size changes, number of joints, size of glazing etc.
Throughout this Technical Report the clauses covering rules frequently express the acceptable change in terms of un-quantified percentages indicated by the letter "X" and an appropriate suffix.
This allows national code authorities to insert their own acceptable limits which will relate to their established fire safety philosophy.
Authorities are encouraged to support the necessary research towards internationally harmonized validated value.
2) Fire engineering calculations: these would be used by an expert in giving advice but will mainly be restricted to the properties indicated below:
· non-loaded elements: this would be restricted to the calculation of temperature rise and deflection of "simple" components and elements;
· loaded element: in addition to the properties permitted for non-loaded elements, calculation at elevated temperature could be permitted for the load-bearing capacity for well-documented materials (steel, concrete, etc.) and for statically determined elements.
In every case the calculation models used by the experts, whatever their source (purchased from software manufacturers or developed in the institution) have to be fully validated by comparison with existing test results and by sensitivity analysis of the various parameters.
3) judgements: for a test result to be extrapolated to cover changes outside those for which calculations or written rules are applicable, the result may still apply subject to some expert judgement being made. The section on judgements highlights the matters that need to be considered and to be explained by the bod
ISO/TR 12470:1998 history
1998ISO/TR 12470:1998 Fire resistance tests - Guidance on the application and extension of results