In-situ checking various mechanical parameters of original nail connections between crossbeams and wooden support, in the framework of an innovative method for rationally dimensioning the crossbeams of panel paintings, applied on an original artwork

This research presents for the first time the rational dimensioning of the stiffness of the crossbeams in an original Panel Painting. Crossbeams typically have a double function: a) to control the deformation of the panel painting when it undergoes climate changes and b) to stiffen the panel painting for handling purposes. If too stiff or too yielding, crossbeams might damage the wooden support or the paint layers; until today the choice of their stiffness was entrusted to the expert but subjective judgment of the Restorers alone, who therefore have been calling for a confrontation with Wood and Engineering Scientists in order to develop more objective criteria. To satisfy this request the research here mentioned has been carried out, to develop a specific protocol allowing for the dimensioning of this stiffness. This protocol is based on an engineering modular approach, and for the first time it has been applied on an original artwork, the Adorazione del bambino e committente attributed to Cesare da Sesto (1514-1520). One of the modules of such protocol is to assess the stiffness of both the crossbeams and the wooden support and, in such framework, this paper presents the non-invasive mechanical tests that were designed and implemented to check in-situ various mechanical parameters (including the axial holding capacity) of the original nail connections between the crossbeams and the wooden support.