ISO/TR 15655:2003

ISO/TR 15655:2003 identifies test methods already in existence and provides guidance on those that need to be developed to characterize the thermo-physical and mechanical properties of structural materials at elevated temperatures for use in fire safety engineering calculations.

It is applicable to materials used in load-bearing construction in which structural and thermal calculations might be required to assess the performance of elements or systems exposed to either standard fire tests, real or design fire heating conditions

It is recognized that the elevated temperature properties of materials can be determined under a variety of conditions. Since fire is a relatively short transient process lasting from a few minutes to several hours, ideally, the properties determined should reflect the transient thermal and loading conditions as well as the duration of heating that may be experienced in practice. However, it is also recognized that some properties are relatively insensitive to the transient conditions and therefore, alternative steady state test methods may be appropriate. Some properties are sensitive to orientation effects, for example timber, and these should be considered with respect to how the tests are conducted.

In cases where materials undergo either a chemical or a physical reaction during the heating process, it might be impossible to determine an individual property. ISO/TR 15655:2003 gives guidance in selecting a test method to determine an effective value representing a combination of properties. It is also recognized that a test specimen may comprise of a small construction such as that used in the testing of masonry. This often involves building a mini assembly to form a pyramid in order to represent the true behaviour.

Apart from the traditional construction materials such as metals, concrete, masonry and wood, the use of plastics and fibre reinforcement is becoming more common. Therefore these materials have also been included in ISO/TR 15655:2003 to reflect possible future changes in design and advances in materials technology.

In the past, the behaviour of jointing systems in fire has only received a little interest yet their behaviour is fundamental to the performance of composite elements and structural frames. ISO/TR 15655:2003 also addresses jointing systems under individual materials, for example welds for steel, glues for timber, they are considered in that section. However, in many cases the end use of an adhesive is not clear or it covers a range of applications. For this reason a separate category for adhesives is included.

For some materials, it has not been possible to identify an existing standard or laboratory procedure for conducting tests at elevated temperatures under either steady state or, transient heating conditions. In these cases, standards for conducting tests at ambient temperature are identified. These may be considered to form the basis for development into a test method suitable at elevated temperatures.