Significance of End Connection Rigidity on the Economic Design of Long-Span Timber Beams

Timber is a sustainable construction material and is increasingly being used in larger structures with large-span beams. The defection limit state often governs the design of these beams, making the accurate estimation of beam deflections essential for their economic design. However, timber beam end connections are often idealised as pin connections, whereas in reality they resist some moments at the service load level. Ignoring the connection rigidity may lead to higher deflection estimation, resulting in uneconomic design. This paper aims to understand the significance of connection rigidity on the economic design of timber beams. The paper conducts a detailed parametric study on the design of long-span timber beams. The parameters used for the study include beam section, span, lateral restraint, and connection rigidity. The study uses a total of 39 Laminated Veneer Lumber (LVL) and Glulam timber sections, which are suitable for long-span beams and currently available in the market. The Australian standard AS1720 is used for the design, and the governing limit states for the design of each beam are identified. The influence of the connection rigidity on that limit state is analysed. The result of the study shows the importance of including connection rigidity for the economic design of long-span timber beams. It identifies the conditions when the connection rigidities are most influential for the design. The findings of the paper highlight the significance of connection rigidity, which has been ignored in the design of timber beams and provide recommendations for its consideration in the design process.