Glueline Integrity in Fire

Mass timber is an increasingly popular material for large and tall buildings. Such buildings typically have higher consequence classes than buildings of traditional timber construction and have higher fire resistance requirements. Architectural demands pushing towards having large surface areas of visible and exposed wood lead to additional fire safety challenges. Previous research has shown that some mass timber products can exhibit glue line integrity failure when exposed to fire, while other mass timber products are not prone to this phenomenon. In practice, it is important to know whether glue line integrity failure occurs, to be able to suitably perform fire resistance calculations (for example using the upcoming version of Eurocode 5) and to be able to predict the fire exposure and duration of fires in real buildings (needed for a performance-based approach). The research presented in this report studies the suitability of a furnace test for determining whether products exhibit glue line integrity failure or not. The study includes the determination of a conservative test duration, by comparisons with conditions of a statistically severe compartment fire. Furthermore, a round robin study with twelve fire tests in furnaces of different labs at different scales, fired with different fuel types has been performed. For all tests, the specimens were made of a mass timber material that does not exhibit glue line integrity failure. The average mass loss rate per unit of exposed area and the average charring rate were determined and assessment criteria were evaluated. Comparisons of the round robin study results have been made, against those of a specific CLT product that has been shown to maintain glue line integrity in numerous furnace and compartment fire tests and a recommendation of a pass/fail criterion is given for a future classification standard