Pyrolysis-Driven Changes in Wood

Timber-framed structures rely on the integrity of metal fixings, yet environmental factors such as heat and moisture movement can significantly affect their performance. This research investigates the withdrawal strength of nails and screws within timber at elevated temperatures, seeking to clarify the major factors at play in this scenario. It concludes with a particular focus on nail failures occurring at around 65°C, and anticipated to go as low as 40°C temperatures now increasingly recorded in the UK due to climate change.Chapter 3 explores the impact of heat on metal fixings embedded in timber, revealing that moisture migration away from heated nails leads to shrinkage and loss of load-bearing capacity. This process results in failure even at temperatures well below pyrolysis thresholds, challenging assumptions about timber stability under moderate heat conditions. The findings raise concerns for fire safety and structural reliability, particularly in older buildings where secondary fixings are crucial for compartmentalisation and fixture stability.Chapter 4 evaluates the feasibility of low-cost CNC and computer vision techniques to analyse the timber-fixing interface. These methods provide a novel approach to identifying shrinkage effects, reinforcing the experimental findings of Chapter 3. By demonstrating the potential for automated assessment, this research contributes to the development of scalable assessment techniques to further under the interface for timber structures. It should be noted that this work was carried out during the pandemic, therefore the novel approach was forced by lack of access to laboratory equipment and the need to be inventive to continue the research under challenging conditions.The discovery that nail failures could occur at 40°C highlights an urgent need to reassess building standards and maintenance practices, given the increasing frequency of such ambient temperatures. This study provides a foundation for further research into material behaviours and monitoring solutions to improve the resilience of timber structures under changing climatic conditions.