TOWARDS HARMONIZED STANDARD FIRE RESISTANCE TESTING

All fire resistance rest furnaces in the EU will shortly be operated i n accordance with EN 1363-1 (ISO 834-1), which specifies the temperatu re-time characteristic of the furnace gases 100 mm from the test speci men. However, even though a test centre complies with this standard, d ifferences in furnace construction, fuel used and mode of operation ca n significantly change the effective heat flux at the surface of the t est specimen. This in turn influences the heating rate and hence the a ssigned fire resistance time of the test specimen. For example, a comp arison between valid fire resistance tests on identical samples of two types of steel beam carried out during 1989 in furnaces at TNO, Delft , and WRFC, Warrington (both gas-fired furnaces), indicated a 30% diff erence in the assigned fire resistance times even though the observed limiting temperatures of the steel beams were similar in each instance . There is evidence that the specimens tested at TNO were subjected to significantly higher incident heat fluxes during the early stages of the test. To achieve harmonized fire resistance testing it is necessar y to subject all test specimens to the same incident heat flux-time ch aracteristic. This will involve furnace standardization and the develo pment of methods for the measurement and control of the incident heat flux at the surface of the test specimen. Some indication is given con cerning the form of the incident heat flux-time characteristic envisag ed for an improved test procedure. (C) 1997 Elsevier Science Ltd.