PSI - Issue 79

Aikaterini Marinelli et al. / Procedia Structural Integrity 79 (2026) 182–189

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Numerical output for combined wind and wave loading indicates that the resulting structural effects are comparable to those produced by wave loading alone. The highest compressive stresses in the horizontal (x direction) are located where the wave contacts the structure. An area of tension occurs at the base on the side the wave impacts, and higher compression occurs up to the breaking point of the wave. The highest compressive stresses in the y-direction take place on the leeward side of the structure where the wave breaks. It should be noted that, with no visual studies of where waves do break on the lighthouse, the height of impact has been reasonably assumed. Horizontal displacements are dominated by the direction of the loading, and largest values are observed around the areas of the rooms within the sandstone regions of the lighthouse (Fig. 5).

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Fig. 5. Numerical output of a design wind and wave loading scenario by distributions of a) normal stresses at x-direction, b) normal stresses at y direction, c) displacement at x-direction To provide a structural assessment of the Bell Rock Lighthouse under the loading scenario that was considered, three possible failure mechanisms are discussed: material failure, overturning and sliding. Based on stresses shown earlier, a safety factor approach considering combinations of stresses based on a post-processing application of a Mohr-Coulomb failure criterion in the form of envelopes suitable for the two materials, confirmed that they are inside the safe domain. Failure due to overturning occurs if the destabilising moment due to the wave impact is higher than the stabilising moment provided by the self-weight. Considering the total weight of the structure as obtained by the numerical model and the equivalent wave force of a 10m high wave, a safety factor of 2.4 was established. Sliding failure occurs when the horizontal force induced by the wave is higher than the frictional force present at the interface between the base of the lighthouse and the reef. Assuming a friction coefficient of 0.7, a 2.5 safety factor against sliding was established in relation to a 10m wave. Considering the criticality of wave loading for the lighthouse as structural response appears highly influenced by the height at which the wave acts, a wave load parametric study would be most useful, to determine the characteristics of a wave that would produce material failure and/or would destabilise the lighthouse. 4. Discussion The findings presented in this study represent a successful pilot investigation into the structural assessment of the historic Bell Rock Lighthouse. A detailed three-dimensional finite element model was developed to simulate the lighthouse's response to representative wind and wave loading conditions. Structural integrity was evaluated with respect to three key failure mechanisms, providing an initial verification of safety under the adopted loading