Reinforcement of Timber Elements in Compression Perpendicular to the Grain using Compressed Wood Dowels

ABSTRACT: In the past decade, there has been an increased focus on the environmental impacts of construction and a movement towards more sustainable construction products. Timber is one such sustainable product that can achieve these environmental targets but, while timber has a high strength-to-weight ratio parallel to the grain, it demonstrates poor strength perpendicular to the grain. As a result, stress perpendicular to the grain is an important factor in the design of timber structures, especially in areas of concentrated loading, such as supports. This paper describes a study, which examines the use of compressed wood dowels as a sustainable alternative to the self-tapping steel screws for reinforcement against perpendicular to the grain compressive stresses. Glued laminated timber specimens were reinforced with 2, 4 and 6 dowels using the same arrangement and dimensions as outlined in Eurocode 5 for self-tapping steel screws. The results show a significant improvement in both load-bearing capacity and stiffness. When compared to the unreinforced condition, the results showed an increase in load-carrying capacity of up to 30% for the 6 dowels arrangement. An increase in stiffness of up to 36% for 6 dowels arrangement was also observed. Additionally, good agreement was found when comparing the experimental results to design equations adapted from recently proposed Eurocode 5 recommendations for compression reinforcement using self-tapping steel screws.