Nonlinear analysis as a diagnostic tool for the strengthening of an old wooden dome

Finite element analysis (FEA), combined with on-site and laboratory tests, might be an effective and versatile tool for studying existing structures, providing useful insights on structural resisting resources and failure mechanisms. When adopted in structural rehabilitation studies, FEA might help the engineer in defining the retrofitting strategies, and in testing their effectiveness. This paper presents an application of nonlinear FEA to the diagnostic study of the wooden dome of Palazzo della Loggia (Brescia, Italy, 1914), in order to assess the feasibility of its preservation, and to aid in planning its strengthening. The FEA demonstrated the influence of local mechanisms, such as clearances and splitting failures at joints, on the large existing crown deflection. Small scale tests were then carried out to study local phenomena and to assess the efficiency of some retrofitting techniques aimed at reinforcing the joints. The numerical model was then used to simulate the strengthening works. The results proved that the wooden roof could be preserved by repairing a few critical joints only, thus considerably limiting the impact of the retrofitting works.