Impact of Strengthening on Shear Stress Distribution in Built-Up Timber Beams
Abstract
The growing emphasis on sustainability has led to an increased use of renewable and low-carbon materials, such as timber, in structural applications. Built-up timber elements are increasingly preferred over solid timber elements due to their superior mechanical properties and dimensional stability. However, strengthening interventions can considerably modify the internal stress distribution within built-up sections. This study presents a theoretical analysis of elastic shear stress distribution at bonding interfaces in built-up beams strengthened with steel plates applied to the tension zone. Different cross-sections, including homogeneous and non-homogeneous rectangular sections, as well as symmetric and asymmetric I-sections, are analyzed. The analysis is performed using the transformed section method, assuming linear elastic material behavior. The results indicate that increasing the steel plate thickness leads to higher interlayer shear stresses, particularly near the first and second layers of the built-up timber sections used in this analysis. In non-homogeneous and asymmetric sections, the stress increase occurs more gradually and is more evenly distributed, whereas homogeneous and symmetric sections display sharper and more concentrated increases near the steel plate. These findings underline the importance of considering not only load-bearing capacity but also interface behavior in strengthening, particularly in aged or historic timber structures where bonding layers may be vulnerable
Keywords
Built-up timber beams, Strengthening, Shear stress, Elastic analysis, Composite section
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