OVERVIEW OF THE WORK WITHIN CEN TC 250/ SC5/ WG12 ASSESMENT AND RETROFITTING OF TIMBER EXISTING STRUCTURE

Engineering design codes for timber structures implicitly address brittle failure modes in single-row multiple-fastener connections by considering an effective number of fasteners. This parameter accounts for the group effect, which considers the load distribution and interaction among the fasteners, as well as the brittle failure of timber. Consequently, the load-carrying capacity of a row of fasteners in multiple-fastener connections is lower than the sum of the capacities of the individual fasteners. Empirical expressions for the effective number of fasteners have been proposed in the literature and are currently used in the design. This study investigates the parameters that influence the effective number of fasteners of timber-to-timber and steel-to-timber connections with stocky, dowel-type fasteners, meaning that they do not undergo plastic deformations, through a numerical approach grounded in linear fracture mechanics. The numerical model aligns well with previous experimental results and provides a novel approach for predicting crack initiation. The group effect is based on a realistic load distribution among fasteners, and the model takes advantage of high computational efficiency.