Structural Assessment of Historical Timber Roof Trusses: The Case of the Croce di Lucca Church in Naples

Large part of the historical heritage is characterised by the presence of timber elements for floors and roof, which need to sustain vertical load and comply with safety prescriptions of current building codes. One of the main stages in the assessment of historical timber structures is the evaluation of material properties. This is not a trivial task, as (i) timber is a complex material, (ii) the presence of defects strongly influences the overall bearing capacity of the element, and (iii) most times exhaustive destructive testing activities may not be feasible. In this respect, the use of resistographic non-destructive tests was proposed in past research as a means to estimate the strength of defect-free wood in longitudinal direction as well as a measure of the material local defectiveness. This approach is formalized in the present paper to derive a design procedure for the structural assessment of ancient timber structures. The procedure is applied to the case study of Croce di Lucca church in Naples. The evaluation of the bearing capacity of the roof structure by means of the proposed experimental methodology reveals significant structural issues in the system, in particular regarding the bottom tie beam.