Luis C. M. da Silva

The capacity of dowel-type timber connections is generally governed by brittle failure modes, such as splitting and row shear failures. In design standards, this is indirectly addressed through the effective number of fasteners concept. This parameter accounts for both the non-uniform load distribution and the interactions among fasteners, which can induce brittle failure before the fasteners’ capacity is fully mobilised. Although the current expressions for the effective number of fasteners in European design codes are based on tests on timber-to-timber connections, they are also applied to other configurations, such as steel-to-timber connections. The present study investigates, through numerical simulation, the validity of existing empirical expressions under various loading conditions and connection arrangements. The numerical model adopted was previously proposed and validated by the authors and is grounded in linear elastic fracture mechanics. The model validation performed herein on the original experimental dataset used to derive the empirical expressions for the effective number of fasteners further strengthens its validity. The parameters influencing the connection response across different configurations are further evaluated, including the fastener slenderness ratio and the spacing between fasteners. The findings reveal that both connection arrangement and loading direction (compression vs tension) substantially affect failure assessment and, by extension, the effective number of fasteners. Specifically, steel-to-timber and tension-loaded connections tend to fail earlier than timber-to-timber connections under compression, thereby leading to a lower effective number of fasteners. These critical factors are not adequately captured in current design equations, underscoring the need for revised approaches, supported by further experimental validation and probabilistic assessment, to improve the reliability of design expressions for the effective number of fasteners.

Cultural heritage preservation requires a deeper understanding of their seismic response and imposes the use of effective strengthening methods. Fibre‐reinforced polymers (FRP) have emerged as an effective solution for strengthening masonry structural elements. The decision over the optimal configuration for a FRP‐based strengthening is a trade‐off between different objective functions such as strength, inelastic stiffness and cost. Although some studies have explored design alternatives and topology optimisation, experimental investigation remains limited, especially regarding the evaluation of seismic response. This study investigates the seismic capacity of unstrengthened and strengthened mortared–masonry arches through tilting table experiments and numerical simulations. The optimal strengthening arrangement is obtained through topology optimisation, and experimental results demonstrate its performance. A three‐dimensional numerical model, following a macro‐modelling approach through the so‐called concrete damage plasticity material model, is adopted. Numerical results are validated with existing literature and experimental data. A parametric study is conducted for full‐scale arches to evaluate the effect of dimensions and the embrace angle of masonry arches. The study reveals that the numerical model successfully replicates masonry arches' nonlinear behaviour and hinge mechanism. In addition, both experimental and numerical results highlight the effectiveness of optimised strengthening placement achieved through topology optimisation.