The repairs to the dome of the Chapel of St. Gennaro's Treasure: an Eighteenth-century dispute between F. Sanfelice and G. Lucchese

In 1708, Ferdinando Sanfelice published “The report on the repairs to the dome of St. Gennaro’s Treasure Chapel” entering the heated debate on the diagnosis of the cracks revealed in the above-mentioned dome. The scientific community split into two different currents of thought, whose main points are: 1) The former considered the dome seriously compromised; the cause of the damage was attributed to an insufficient thickness of the tambour and therefore it proposed to add a further iron bandaging, in addition to the three existing reinforcement rings. 2) The latter dissented and reputed that the fractures didn't endanger the stability of the structure. For the experts that supported this current of thought, the cause was to be attributed exclusively to the excessive weight of the small lantern and not " per difetto de’ muri di fabbrica " ( to the thickness of the main walls); and in fact, the first repair was the substitution of the stone lantern with an oaken one. In this context, we find Ferdinando Sanfelice engaged in a heated debate with all the advocates of the dome encirclement and particularly with Lucchese. The intention of this note is to interpret the Ferdinando Sanfelice and Giuseppe Lucchese statements in the light of the XVIII century static theories on the vaulted buildings. Particularly, the two reports will be reread through the treatises Statica degli Edifici and Voltimetria Retta by Vincenzo Lamberti, Neapolitan engineer of the XVIII century, with reference to other coeval handbooks. Subsequently, the validity of the statements will be tested with an appropriate numerical method, according to the contemporary techniques of modelling masonries.