Fire Behaviour and Fire Stability Test of Wood Species and Joint Types

Abstract

The construction industry has shown a significant interest in timber due to its sustainability, leading to widespread use. However, choosing the ideal material can be challenging due to the varying performance of different types of wood, especially considering its combustible nature. Besides, the joints in the timber structure are considered the weakest part of the structure. The physical separation in the wooden jointed sample due to the fire is termed here as the failure of the sample in other words the stability of the sample. In the current state of the art, the failure is influenced by the behaviour of the wood under fire, along with cracking, and opening occurring due to the jointed glue line. Therefore, in this study, an experimental investigation has been performed focusing on two major goals - to understand the behaviour of the jointed wood in developing fire and to understand the stability of the jointed sample under fully developed fire. To study this behaviour, in total 160 small-scale tests were performed, where 100 cone calorimeter tests and 60 fire stability tests were performed. Three different types of wood namely Pine, Spruce, and Beech, and 5 different joints (no joint, butt joint, half-lap joint, 3-finger joint, and 6-finger joint) were analysed. Also, two different thicknesses 24 mm and 42 mm of Spruce wood were evaluated. Besides, in the cone calorimeter test, three different heat flux levels (35, 50, & 65 kW/m2) were tested as part of the thesis work. From these tests, the changes in the fire behaviour were observed for three different woods in the second peak heat release. Cracks and deformation during the burning were noticeable influential factors. The method developed in this work is suitable for observing the failure time. Nevertheless, there are some limitations to this approach. The failure in the jointed timber has been observed mostly from the glue line. The thermal penetration through the sample and charring rate are indications of this phenomenon and are considered as important tools for understanding the failure of the sample. Even so, none of the investigated features alone showed the same effect on the heated depth as that observed in the experimental study. This highlights the need for further research to understand the mechanisms causing the failure of the jointed wood.

Popular Abstract

Timber is gaining popularity for sustainability, quick assembly, and aesthetic value. Recently, the uses of an engineered product like Glue laminated timber and Cross-laminated has increased which required glued joints to produce them. Not only just producing this timber specimen, but also in any timber construction joints exist to minimize wastage, and support the structure. This jointed part is considered the weakest part of the structure. So, it is really important to include the behaviour of joints in fire design. Although the wood behaviour is widely described, the fire behaviour of glued joints still needs to be explored.
This research is structured around two main goals. Firstly, it aims to investigate the behaviour of five different types of jointed wood across various wood species during the developing fire stage. Secondly, it focuses on understanding the stability (failure of the joints) of these jointed wood structures under fully developed fire conditions. To achieve these goals, two distinct tests were conducted: the Cone Calorimeter test and the Fire Stability test. Through 160 small-scale tests, including cone calorimeter and fire stability tests, Pine, Spruce, and Beech woods with various joints and thicknesses were analyzed. For the cone calorimeter test, the ISO 5660:2015 standard was followed, and the fire stability test was conducted on a small scale at the BAM laboratory to meet the specified objectives. Detailed descriptions of the test setup can be found in the report.
The main results revealed that different types of wood and joints exhibit varying behaviours in terms of the time of ignition, first and second peak release, time to reach the first and second peak, mass loss rate, and total heat release when subjected to fire. Differences have been observed in the failure time, and thermal penetration among jointed wood due to density, and thermal conductivity differences. Understanding these differences is crucial for designing buildings that can better withstand fires. The small-scale tests were the focus of this work. Furthermore, the findings suggest that further research is necessary to fully comprehend the behaviour of wood joints in fire scenarios, which can ultimately enhance building safety standards.

• author: Mannan, Maria Binte
• supervisor: Patrick Van Hees
• organization: Division of Fire Safety Engineering
• course: VBRM05 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Timber, Timber Joints, Wood species, Pine, Spruce, Beech, Fire Behaviour, Fire Stability, Bench scale test, Cone calorimeter test, Temperature profile, Heat release rate.
• publication/series: LUTVDG/TVBB
• report number: 5722
• other publication id: LUTVDG/TVBB—5722-SE
• language: English
• id: 9159320
• date added to LUP: 2024-06-11 07:38:20
• date last changed: 2024-06-11 07:38:20